ADC12DS105
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SNAS382E – SEPTEMBER 2006 – REVISED APRIL 2013
ADC12DS105 Dual 12-Bit, 105 MSPS A/D Converter with Serial LVDS Outputs
Check for Samples: ADC12DS105
FEATURES
DESCRIPTION
•
•
•
•
•
•
The ADC12DS105 is a high-performance CMOS
analog-to-digital converter capable of converting two
analog input signals into 12-bit digital words at rates
up to 105 Mega Samples Per Second (MSPS). The
digital outputs are serialized and provided on
differential LVDS signal pairs. This converter uses a
differential, pipelined architecture with digital error
correction and an on-chip sample-and-hold circuit to
minimize power consumption and the external
component count, while providing excellent dynamic
performance. The ADC12DS105 may be operated
from a single +3.0V or 3.3V power supply. A powerdown feature reduces the power consumption to very
low levels while still allowing fast wake-up time to full
operation. The differential inputs accept a 2V full
scale differential input swing. A stable 1.2V internal
voltage reference is provided, or the ADC12DS105
can be operated with an external 1.2V reference. The
selectable
duty
cycle
stabilizer
maintains
performance over a wide range of clock duty cycles.
A serial interface allows access to the internal
registers for full control of the ADC12DS105's
functionality. The ADC12DS105 is available in a 60lead WQFN package and operates over the industrial
temperature range of −40°C to +85°C
1
2
Clock Duty Cycle Stabilizer
Single +3.0 or 3.3V Supply Operation
Serial LVDS Outputs
Serial Control Interface
Overrange Outputs
60-pin WQFN Package, (9x9x0.8mm, 0.5mm
pin-pitch)
APPLICATIONS
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•
•
•
•
High IF Sampling Receivers
Wireless Base Station Receivers
Test and Measurement Equipment
Communications Instrumentation
Portable Instrumentation
KEY SPECIFICATIONS
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•
•
•
•
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Resolution: 12 Bits
Conversion Rate: 105 MSPS
SNR (fIN = 240 MHz): 68.5 dBFS (typ)
SFDR (fIN = 240 MHz): 83 dBFS (typ)
Full Power Bandwidth: 1 GHz (typ)
Power Consumption: 1 W (typ)
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006–2013, Texas Instruments Incorporated
ADC12DS105
SNAS382E – SEPTEMBER 2006 – REVISED APRIL 2013
www.ti.com
PD_A
SPI_EN
SCSb
SDI
SDO
SCLK
DRGND
VDR
N/C
DLC
WAM
ORA
57
56
55
54
53
52
51
49
48
47
46
50
VREF
VA
58
VA
59
60
Connection Diagram
AGND
VINA-
1
45
OUTCLK+
2
44
OUTCLK-
VINA+
3
43
FRAME+
AGND
VRPA
4
42
FRAME-
5
41
VRNA
6
40
N/C
VDR
VCMOA
7
39
DRGND
VA
8
38
SD1_A+
VCMOB
9
37
SD1_A-
VRNB
10
36
SD0_A+
VRPB
11
35
SD0_A-
AGND
VINB+
12
34
SD1_B+
13
33
SD1_B-
VINB-
14
32
SD0_B+
AGND
15
31
SD0_B-
ADC12DS105
(top view)
17
18
19
20
21
22
23
24
25
26
27
28
29
30
VA
CLK
PD_B
N/C
N/C
N/C
DLL_Lock
DRGND
VDR
TEST
Reset_DLL
LVDS_Bias
ORB
OF/DCS
16
VA
* Exposed Pad
Figure 1. WQFN Package
See Package Number NKA0060A
Block Diagram
ORA
2
2
VINA
Ref.Outputs
VREF
12-Bit Pipelined
ADC Core
Parallel
-toSerial
2
Reference
A
3
Reference
B
2
12-Bit Pipelined
ADC Core
DLL
&
Timing
Generation
2
CHANNEL A
SD1_A
FRAME
2
OUTCLK
2
VINB
SD0_A
3
CLK
Ref.Outputs
12
12
Parallel
-toSerial
2
SD0_B
CHANNEL B
SD1_B
ORB
SCSb
SCLK
SPI_EN
SDI
SDO
2
SPI
Interface
&
Control
Registers
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Pin Descriptions and Equivalent Circuits
Pin No.
Symbol
Equivalent Circuit
Description
ANALOG I/O
3
13
VINA+
VINB+
2
14
VINAVINB-
5
11
VRPA
VRPB
7
9
VCMOA
VCMOB
VA
Differential analog input pins. The differential full-scale input signal
level is 2VP-P with each input pin signal centered on a common mode
voltage, VCM.
AGND
VA
VA
VA
6
10
VRNA
VRNB
VA
These pins should each be bypassed to AGND with a low ESL
(equivalent series inductance) 0.1 µF capacitor placed very close to
the pin to minimize stray inductance. An 0201 size 0.1 µF capacitor
should be placed between VRP and VRN as close to the pins as
possible, and a 1 µF capacitor should be placed in parallel.
VRP and VRN should not be loaded. VCMO may be loaded to 1mA for
use as a temperature stable 1.5V reference.
It is recommended to use VCMO to provide the common mode
voltage, VCM, for the differential analog inputs.
AGND
AGND
Reference Voltage. This device provides an internally developed
1.2V reference. When using the internal reference, VREF should be
decoupled to AGND with a 0.1 µF and a 1µF, low equivalent series
inductance (ESL) capacitor.
This pin may be driven with an external 1.2V reference voltage.
This pin should not be used to source or sink current.
VA
59
VREF
29
LVDS_Bias
LVDS Driver Bias Resistor is applied from this pin to Analog Ground.
The nominal value is 3.6KΩ
AGND
DIGITAL I/O
18
28
CLK
VA
The clock input pin.
The analog inputs are sampled on the rising edge of the clock input.
Reset_DLL input. This pin is normally low. If the input clock
frequency is changed abruptly, the internal timing circuits may
become unlocked. Cycle this pin high for 1 microsecond to re-lock
the DLL. The DLL will lock in several microseconds after Reset_DLL
is asserted.
Reset_DLL
AGND
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Pin Descriptions and Equivalent Circuits (continued)
Pin No.
Symbol
Equivalent Circuit
VA
19
OF/DCS
AGND
57
20
This is a two-state input controlling Power Down.
PD = VA, Power Down is enabled and power dissipation is reduced.
PD = AGND, Normal operation.
Note: This signal has no effect when SPI_EN is high and the SPI
interface is enabled.
PD_A
PD_B
VA
27
47
TEST
Test Mode. When this signal is asserted high, a fixed test pattern
(101001100011 msb->lsb) is sourced at the data outputs.
With this signal deasserted low, the device is in normal operation
mode.
Note: This signal has no effect when SPI_EN is high and the SPI
interface is enabled.
WAM
Word Alignment Mode.
In single-lane mode this pin must be set to logic-0.
In dual-lane mode only, when this signal is at logic-0 the serial data
words are offset by half-word. With this signal at logic-1 the serial
data words are aligned with each other.
Note: This signal has no effect when SPI_EN is high and the SPI
interface is enabled.
AGND
48
Dual-Lane Configuration. The dual-lane mode is selected when this
signal is at logic-0. With this signal at logic-1, all data is sourced on a
single lane (SD1_x) for each channel.
Note: This signal has no effect when SPI_EN is high and the SPI
interface is enabled.
DLC
VDR
45
44
OUTCLK+
OUTCLK-
+
-
+
43
42
FRAME+
FRAME-
DRGND
4
Description
This is a four-state pin controlling the input clock mode and output
data format.
OF/DCS = VA, output data format is 2's complement without duty
cycle stabilization applied to the input clock
OF/DCS = AGND, output data format is offset binary, without duty
cycle stabilization applied to the input clock.
OF/DCS = (2/3)*VA, output data is 2's complement with duty cycle
stabilization applied to the input clock
OF/DCS = (1/3)*VA, output data is offset binary with duty cycle
stabilization applied to the input clock.
Note: This signal has no effect when SPI_EN is high and the SPI
interface is enabled.
Serial Clock. This pair of differential LVDS signals provides the serial
clock that is synchronous with the Serial Data outputs. A bit of serial
data is provided on each of the active serial data outputs with each
falling and rising edge of this clock. This differential output is always
enabled while the device is powered up. In power-down mode this
output is held in logic-low state. A 100-ohm termination resistor must
always be used between this pair of signals at the far end of the
transmission line.
Serial Data Frame. This pair of differential LVDS signals transitions
at the serial data word boundaries. The SD1_A+/- and SD1_B+/output words always begin with the rising edge of the Frame signal.
The falling edge of the Frame signal defines the start of the serial
data word presented on the SD0_A+/- and SD0_B+/- signal pairs in
the Dual-Lane mode. This differential output is always enabled while
the device is powered up. In power-down mode this output is held in
logic-low state. A 100-ohm termination resistor must always be used
between this pair of signals at the far end of the transmission line.
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Pin Descriptions and Equivalent Circuits (continued)
Pin No.
38
37
Symbol
Equivalent Circuit
SD1_A+
SD1_A-
VDR
34
33
SD1_B+
SD1_B-
+
-
+
36
35
Description
Serial Data Output 1 for Channel A. This is a differential LVDS pair
of signals that carries channel A ADC’s output in serialized form. The
serial data is provided synchronous with the OUTCLK output. In
Single-Lane mode each sample’s output is provided in succession.
In Dual-Lane mode every other sample output is provided on this
output. This differential output is always enabled while the device is
powered up. In power-down mode this output holds the last logic
state. A 100-ohm termination resistor must always be used between
this pair of signals at the far end of the transmission line.
SD0_A+
SD0_ADRGND
Serial Data Output 1 for Channel B. This is a differential LVDS pair
of signals that carries channel B ADC’s output in serialized form. The
serial data is provided synchronous with the OUTCLK output. In
Single-Lane mode each sample’s output is provided in succession.
In Dual-Lane mode every other sample output is provided on this
output. This differential output is always enabled while the device is
powered up. In power-down mode this output holds the last logic
state. A 100-ohm termination resistor must always be used between
this pair of signals at the far end of the transmission line.
Serial Data Output 0 for Channel A. This is a differential LVDS pair
of signals that carries channel A ADC’s alternating samples’ output
in serialized form in Dual-Lane mode. The serial data is provided
synchronous with the OUTCLK output. In Single-Lane mode this
differential output is held in high impedance state. This differential
output is always enabled while the device is powered up. In powerdown mode this output holds the last logic state. A 100-ohm
termination resistor must always be used between this pair of signals
at the far end of the transmission line.
Serial Data Output 0 for Channel B. This is a differential LVDS pair
of signals that carries channel B ADC’s alternating samples’ output
in serialized form in Dual-Lane mode. The serial data is provided
synchronous with the OUTCLK output. In Single-Lane mode this
differential output is held in high impedance state. This differential
output is always enabled while the device is powered up. In powerdown mode this output holds the last logic state. A 100-ohm
termination resistor must always be used between this pair of signals
at the far end of the transmission line.
32
31
SD0_B+
SD0_B-
56
SPI_EN
SPI Enable: The SPI interface is enabled when this signal is
asserted high. In this case the direct control pins have no effect.
When this signal is deasserted, the SPI interface is disabled and the
direct control pins are enabled.
55
SCSb
Serial Chip Select: While this signal is asserted SCLK is used to
accept serial data present on the SDI input and to source serial data
on the SDO output. When this signal is deasserted, the SDI input is
ignored and the SDO output is in tri-state mode.
52
SCLK
Serial Clock: Serial data are shifted into and out of the device
synchronous with this clock signal.
54
SDI
53
SDO
Serial Data-Out: Serial data are shifted out of the device on this pin
while SCSb signal is asserted. This output is in tri-state mode when
SCSb is deasserted.
46
30
ORA
ORB
Overrange. These CMOS outputs are asserted logic-high when their
respective channel’s data output is out-of-range in either high or low
direction.
24
DLL_Lock
DLL_Lock Output. When the internal DLL is locked to the input CLK,
this pin outputs a logic high. If the input CLK is changed abruptly, the
internal DLL may become unlocked and this pin will output a logic
low. Cycle Reset_DLL (pin 28) to re-lock the DLL to the input CLK.
VA
AGND
VDR
DRGND
VA
DGND
Serial Data-In: Serial data are shifted into the device on this pin
while SCSb signal is asserted.
ANALOG POWER
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Pin Descriptions and Equivalent Circuits (continued)
Pin No.
Symbol
8, 16, 17, 58,
60
VA
1, 4, 12, 15,
Exposed Pad
AGND
Equivalent Circuit
Description
Positive analog supply pins. These pins should be connected to a
quiet source and be bypassed to AGND with 0.1 µF capacitors
located close to the power pins.
The ground return for the analog supply.
DIGITAL POWER
26, 40, 50
VDR
25, 39, 51
DRGND
Positive driver supply pin for the output drivers. This pin should be
connected to a quiet voltage source and be bypassed to DRGND
with a 0.1 µF capacitor located close to the power pin.
The ground return for the digital output driver supply. This pins
should be connected to the system digital ground, but not be
connected in close proximity to the ADC's AGND pins.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings (1) (2) (3)
−0.3V to 4.2V
Supply Voltage (VA, VDR)
−0.3V to (VA +0.3V)
Voltage on Any Pin (Not to exceed 4.2V)
Input Current at Any Pin other than Supply Pins (4)
±5 mA
Package Input Current (4)
±50 mA
Max Junction Temp (TJ)
+150°C
Thermal Resistance (θJA)
ESD Rating
30°C/W
Human Body Model (5)
2500V
Machine Model (5)
250V
−65°C to +150°C
Storage Temperature
Soldering process must comply with Reflow Temperature Profile specifications. Refer to www.ti.com/packaging. (6)
(1)
(2)
(3)
(4)
(5)
(6)
All voltages are measured with respect to GND = AGND = DRGND = 0V, unless otherwise specified.
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is ensured to be functional, but do not ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance
characteristics may degrade when the device is not operated under the listed test conditions. Operation of the device beyond the
maximum Operating Ratings is not recommended.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
When the input voltage at any pin exceeds the power supplies (that is, VIN < AGND, or VIN > VA), the current at that pin should be
limited to ±5 mA. The ±50 mA maximum package input current rating limits the number of pins that can safely exceed the power
supplies with an input current of ±5 mA to 10.
Human Body Model is 100 pF discharged through a 1.5 kΩ resistor. Machine Model is 220 pF discharged through 0 Ω
Reflow temperature profiles are different for lead-free and non-lead-free packages.
Operating Ratings (1) (2)
−40°C ≤ TA ≤ +85°C
Operating Temperature
Supply Voltage (VA=VDR)
Clock Duty Cycle
+2.7V to +3.6V
(DCS Enabled)
(DCS Disabled)
VCM
(2)
6
45/55 %
1.4V to 1.6V
≤100mV
|AGND-DRGND|
(1)
30/70 %
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is ensured to be functional, but do not ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance
characteristics may degrade when the device is not operated under the listed test conditions. Operation of the device beyond the
maximum Operating Ratings is not recommended.
All voltages are measured with respect to GND = AGND = DRGND = 0V, unless otherwise specified.
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Converter Electrical Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, VCM = VCMO, CL = 5 pF/pin. Typical values are for TA = 25°C. Boldface limits apply for TMIN ≤ TA ≤
TMAX. All other limits apply for TA = 25°C (1) (2)
Parameter
Test Conditions
Typical (3)
Limits
Units
(Limits)
STATIC CONVERTER CHARACTERISTICS
Resolution with No Missing Codes
INL
Integral Non Linearity
±0.5
12
Bits (min)
2
LSB (max)
-2
LSB (min)
0.8
LSB (max)
DNL
Differential Non Linearity
±0.3
-0.8
LSB (min)
PGE
Positive Gain Error
0.15
±1
%FS (max)
NGE
Negative Gain Error
0.07
±1
%FS (max)
TC PGE
Positive Gain Error Tempco
−40°C ≤ TA ≤ +85°C
TC NGE
Negative Gain Error Tempco
−40°C ≤ TA ≤ +85°C
VOFF
Offset Error
TC VOFF
Offset ErrorTempco
ppm/°C
ppm/°C
0.03
±0.55
Under Range Output Code
0
0
Over Range Output Code
4095
4095
−40°C ≤ TA ≤ +85°C
%FS (max)
ppm/°C
REFERENCE AND ANALOG INPUT CHARACTERISTICS
VCMO
Common Mode Output Voltage
1.5
1.4
1.6
V (min)
V (max)
VCM
Analog Input Common Mode Voltage
1.5
1.4
1.6
V (min)
V (max)
CIN
VIN Input Capacitance (each pin to
GND) (4)
VIN = 1.5 Vdc ± 0.5
V
(CLK LOW)
8.5
(CLK HIGH)
3.5
pF
1.17
1.21
V (min)
V (max)
VREF
Internal Reference Voltage
TC VREF
Internal Reference Voltage Tempco
18
ppm/°C
VRP
Internal Reference Top
2.0
V
VRN
Internal Reference Bottom
1.0
Internal Reference Accuracy
EXT
VREF
(1)
(2)
(3)
(4)
1.18
pF
−40°C ≤ TA ≤ +85°C
(VRP-VRN)
External Reference Voltage
V
0.97
0.89
1.06
V (min)
V (max)
1.2
1.176
1.224
V (min)
V (max)
The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided
current is limited per Note 4 of the Absolute Maximum Ratings Table. However, errors in the A/D conversion can occur if the input goes
above 2.6V or below GND as described in the Operating Ratings section. See Figure 2.
With a full scale differential input of 2VP-P , the 12-bit LSB is 488 µV.
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
The input capacitance is the sum of the package/pin capacitance and the sample and hold circuit capacitance.
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Dynamic Converter Electrical Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, VCM = VCMO, CL = 5 pF/pin, . Typical values are for TA = 25°C. Boldface limits apply for TMIN ≤ TA
≤ TMAX. All other limits apply for TA = 25°C (1) (2)
Parameter
Test Conditions
Typical (3)
Limits
Units
(Limits) (4)
DYNAMIC CONVERTER CHARACTERISTICS, AIN= -1dBFS
FPBW
Full Power Bandwidth
-1 dBFS Input, −3 dB Corner
fIN = 10 MHz
SNR
SFDR
ENOB
THD
H2
(2)
(3)
(4)
8
Effective Number of Bits
Total Harmonic Disortion
Third Harmonic Distortion
SINAD
(1)
Spurious Free Dynamic Range
Second Harmonic Distortion
H3
IMD
Signal-to-Noise Ratio
Signal-to-Noise and Distortion Ratio
Intermodulation Distortion
1.0
GHz
71
dBFS
fIN = 70 MHz
70
fIN = 240 MHz
68.5
fIN = 10 MHz
88
fIN = 70 MHz
85
fIN = 240 MHz
83
fIN = 10 MHz
11.5
fIN = 70 MHz
11.3
fIN = 240 MHz
11
fIN = 10 MHz
−86
fIN = 70 MHz
−85
fIN = 240 MHz
−80
fIN = 10 MHz
−90
fIN = 70 MHz
−88
fIN = 240 MHz
−83
fIN = 10 MHz
−88
fIN = 70 MHz
−85
fIN = 240 MHz
−83
fIN = 10 MHz
70.8
fIN = 70 MHz
69.9
fIN = 240 MHz
68.2
fIN = 19.5 and 20.5 MHz,
each -7dBFS
-82
dBFS
67.4
dBFS
dBFS
dBFS
76.5
dBFS
Bits
Bits
10.7
Bits
dBFS
dBFS
-74
dBFS
dBFS
dBFS
-76.5
dBFS
dBFS
dBFS
-76.5
dBFS
dBFS
dBFS
66.5
dBFS
dBFS
The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided
current is limited per Note 4 of the Absolute Maximum Ratings Table. However, errors in the A/D conversion can occur if the input goes
above 2.6V or below GND as described in the Operating Ratings section. See Figure 2.
With a full scale differential input of 2VP-P , the 12-bit LSB is 488 µV.
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
This parameter is specified in units of dBFS - indicating the value that would be attained with a full-scale input signal.
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Logic and Power Supply Electrical Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, VCM = VCMO, CL = 5 pF/pin. Typical values are for TA = 25°C. Boldface limits apply for TMIN ≤ TA ≤
TMAX. All other limits apply for TA = 25°C (1) (2)
Parameter
Test Conditions
Typical (3)
Limits
Units
(Limits)
DIGITAL INPUT CHARACTERISTICS (CLK, PD_A,PD_B,SCSb,SPI_EN,SCLK,SDI,TEST,WAM,DLC)
VIN(1)
Logical “1” Input Voltage
VD = 3.6V
2.0
V (min)
VIN(0)
Logical “0” Input Voltage
VD = 3.0V
0.8
V (max)
IIN(1)
Logical “1” Input Current
VIN = 3.3V
10
µA
IIN(0)
Logical “0” Input Current
VIN = 0V
−10
µA
CIN
Digital Input Capacitance
5
pF
DIGITAL OUTPUT CHARACTERISTICS (ORA,ORB,SDO,DLL_Lock)
VOUT(1)
Logical “1” Output Voltage
IOUT = −0.5 mA
VOUT(0)
Logical “0” Output Voltage
IOUT = 1.6 mA
+ISC
Output Short Circuit Source Current
VOUT = 0V
−10
mA
−ISC
Output Short Circuit Sink Current
VOUT = VDR
10
mA
COUT
Digital Output Capacitance
5
pF
1.2
V (min)
0.4
V (max)
POWER SUPPLY CHARACTERISTICS
IA
Analog Supply Current
Full Operation
240
270
mA (max)
IDR
Digital Output Supply Current
Full Operation
70
80
mA
1000
1130
mW (max)
Power Consumption
Power Down Power Consumption
(1)
(2)
(3)
Clock disabled
33
mW
The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided
current is limited per Note 4 of the Absolute Maximum Ratings Table. However, errors in the A/D conversion can occur if the input goes
above 2.6V or below GND as described in the Operating Ratings section. See Figure 2.
With a full scale differential input of 2VP-P , the 12-bit LSB is 488 µV.
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
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Timing and AC Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, VCM = VCMO, CL = 5 pF/pin. Typical values are for TA = 25°C. Timing measurements are taken at
50% of the signal amplitude. Boldface limits apply for TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (1) (2)
Parameter
Typical (3)
Test Conditions
Limits
Units
(Limits)
Maximum Clock Frequency
In Single-Lane Mode
In Dual-Lane Mode
65
105
MHz (max)
Minimum Clock Frequency
In Single-Lane Mode
In Dual-Lane Mode
25
52.5
MHz (min)
tCONV
Conversion Latency
Single-Lane Mode
Dual-Lane, Offset Mode
Dual-Lane, Word Aligned Mode
7.5
8
9
Clock Cycles
tAD
Aperture Delay
0.6
ns
tAJ
Aperture Jitter
0.1
ps rms
(1)
(2)
(3)
The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided
current is limited per Note 4 of the Absolute Maximum Ratings Table. However, errors in the A/D conversion can occur if the input goes
above 2.6V or below GND as described in the Operating Ratings section. See Figure 2.
With a full scale differential input of 2VP-P , the 12-bit LSB is 488 µV.
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
Serial Control Interface Timing and AC Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = 3.3V, VDR = +3.0V, Internal VREF =
+1.2V, fCLK = 105 MHz, VCM = VCMO, CL = 5 pF/pin. Typical values are for TA = 25°C. Timing measurements are taken at 50%
of the signal amplitude. Boldface limits apply for TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (1) (2)
Parameter
fSCLK
Serial Clock Frequency
Typical (3)
Test Conditions
fSCLK = fCLK/10
Limits
Units
(Limits)
10.5
MHz (max)
% (min)
% (max)
tPH
SCLK Pulse Width - High
% of SCLK Period
40
60
tPL
SCLK Pulse Width - Low
% of SCLK Period
40
60
% (min)
% (max)
tSU
SDI Setup Time
5
ps (min)
tH
SDI Hold Time
5
ns (min)
tODZ
SDO Driven-to-Tri-State Time
40
50
ns (max)
tOZD
SDO Tri-State-to-Driven Time
15
20
ns (max)
tOD
SDO Output Delay Time
15
20
ns (max)
tCSS
SCSb Setup Time
5
10
ns (min)
tCSH
SCSb Hold Time
5
10
tIAG
(1)
(2)
(3)
10
Inter-Access Gap
Minimum time SCSb must be deasserted
between accesses
3
ns (min)
Cycles of
SCLK
The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided
current is limited per Note 4 of the Absolute Maximum Ratings Table. However, errors in the A/D conversion can occur if the input goes
above 2.6V or below GND as described in the Operating Ratings section. See Figure 2.
With a full scale differential input of 2VP-P , the 12-bit LSB is 488 µV.
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
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LVDS Electrical Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, VCM = VCMO, CL = 5 pF/pin. Typical values are for TA = 25°C. Timing measurements are taken at
50% of the signal amplitude. Boldface limits apply for TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (1) (2)
Parameter
Test Conditions
Typical (3)
Limits
Units
(Limits)
350
250
450
mV (min)
mV (max)
±25
mV (max)
1.125
1.375
V (min)
V (max)
±25
mV (max)
LVDS DC CHARACTERISTICS
VOD
Output Differential Voltage
(SDO+) - (SDO-)
RL = 100Ω
delta
VOD
Output Differential Voltage Unbalance
RL = 100Ω
VOS
Offset Voltage
RL = 100Ω
delta VOS Offset Voltage Unbalance
RL = 100Ω
IOS
DO = 0V, VIN = 1.1V,
Output Short Circuit Current
1.25
-10
mA (max)
ns
LVDS OUTPUT TIMING AND SWITCHING CHARACTERISTICS
tDP
Output Data Bit Period
Dual-Lane Mode
1.59
tHO
Output Data Edge to Output Clock Edge
Hold Time (4)
Dual-Lane Mode
750
450
ps
tSUO
Output Data Edge to Output Clock Edge
Set-Up Time (4)
Dual-Lane Mode
800
500
ps
tFP
Frame Period
Dual-Lane Mode
19.05
45
55
% (min)
% (max)
(4)
tFDC
Frame Clock Duty Cycle
tDFS
Data Edge to Frame Edge Skew
50% to 50%
15
ps
tODOR
Output Delay of OR output
From rising edge of CLK to ORA/ORB
valid
4
ns
(1)
(2)
(3)
(4)
50
ns
The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided
current is limited per Note 4 of the Absolute Maximum Ratings Table. However, errors in the A/D conversion can occur if the input goes
above 2.6V or below GND as described in the Operating Ratings section. See Figure 2.
With a full scale differential input of 2VP-P , the 12-bit LSB is 488 µV.
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
This parameter is specified by design and/or characterization and is not tested in production.
VA
I/O
To Internal Circuitry
AGND
Figure 2.
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Specification Definitions
APERTURE DELAY is the time after the falling edge of the clock to when the input signal is acquired or held for
conversion.
APERTURE JITTER (APERTURE UNCERTAINTY) is the variation in aperture delay from sample to sample.
Aperture jitter manifests itself as noise in the output.
CLOCK DUTY CYCLE is the ratio of the time during one cycle that a repetitive digital waveform is high to the
total time of one period. The specification here refers to the ADC clock input signal.
COMMON MODE VOLTAGE (VCM) is the common DC voltage applied to both input terminals of the ADC.
CONVERSION LATENCY is the number of clock cycles between initiation of conversion and when that data is
presented to the output driver stage. Data for any given sample is available at the output pins the Pipeline Delay
plus the Output Delay after the sample is taken. New data is available at every clock cycle, but the data lags the
conversion by the pipeline delay.
CROSSTALK is coupling of energy from one channel into the other channel.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of the maximum deviation from the ideal step size of 1
LSB.
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE BITS) is another method of specifying Signal-to-Noise
and Distortion Ratio or SINAD. ENOB is defined as (SINAD - 1.76) / 6.02 and says that the converter is
equivalent to a perfect ADC of this (ENOB) number of bits.
FULL POWER BANDWIDTH is a measure of the frequency at which the reconstructed output fundamental
drops 3 dB below its low frequency value for a full scale input.
GAIN ERROR is the deviation from the ideal slope of the transfer function. It can be calculated as:
Gain Error = Positive Full Scale Error − Negative Full Scale Error
(1)
It can also be expressed as Positive Gain Error and Negative Gain Error, which are calculated as:
PGE = Positive Full Scale Error - Offset Error NGE = Offset Error - Negative Full Scale Error
(2)
INTEGRAL NON LINEARITY (INL) is a measure of the deviation of each individual code from a best fit straight
line. The deviation of any given code from this straight line is measured from the center of that code value.
INTERMODULATION DISTORTION (IMD) is the creation of additional spectral components as a result of two
sinusoidal frequencies being applied to the ADC input at the same time. It is defined as the ratio of the power in
the intermodulation products to the total power in the original frequencies. IMD is usually expressed in dBFS.
LSB (LEAST SIGNIFICANT BIT) is the bit that has the smallest value or weight of all bits. This value is VFS/2n,
where “VFS” is the full scale input voltage and “n” is the ADC resolution in bits.
VD+
VDVOS
VOD
GND
VOD = | VD+ - VD- |
LVDS Differential Output Voltage (VOD) is the absolute value of the difference between the differential output
pair voltages (VD+ and VD-), each measured with respect to ground.
MISSING CODES are those output codes that will never appear at the ADC outputs. The ADC is specified not to
have any missing codes.
MSB (MOST SIGNIFICANT BIT) is the bit that has the largest value or weight. Its value is one half of full scale.
NEGATIVE FULL SCALE ERROR is the difference between the actual first code transition and its ideal value of
½ LSB above negative full scale.
OFFSET ERROR is the difference between the two input voltages [(VIN+) – (VIN-)] required to cause a transition
from code 2047 to 2048.
12
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OUTPUT DELAY is the time delay after the falling edge of the clock before the data update is presented at the
output pins.
PIPELINE DELAY (LATENCY) See CONVERSION LATENCY.
POSITIVE FULL SCALE ERROR is the difference between the actual last code transition and its ideal value of
1½ LSB below positive full scale.
POWER SUPPLY REJECTION RATIO (PSRR) is a measure of how well the ADC rejects a change in the power
supply voltage. PSRR is the ratio of the Full-Scale output of the ADC with the supply at the minimum DC supply
limit to the Full-Scale output of the ADC with the supply at the maximum DC supply limit, expressed in dB.
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in dB, of the rms value of the input signal to the rms
value of the sum of all other spectral components below one-half the sampling frequency, not including
harmonics or DC.
SIGNAL TO NOISE PLUS DISTORTION (S/N+D or SINAD) Is the ratio, expressed in dB, of the rms value of the
input signal to the rms value of all of the other spectral components below half the clock frequency, including
harmonics but excluding d.c.
SPURIOUS FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the rms values of the
input signal and the peak spurious signal, where a spurious signal is any signal present in the output spectrum
that is not present at the input.
TOTAL HARMONIC DISTORTION (THD) is the ratio, expressed in dB, of the rms total of the first six harmonic
levels at the output to the level of the fundamental at the output. THD is calculated as
(3)
where f1 is the RMS power of the fundamental (output) frequency and f2 through f7 are the RMS power of the first
six harmonic frequencies in the output spectrum.
SECOND HARMONIC DISTORTION (2ND HARM) is the difference expressed in dB, between the RMS power in
the input frequency at the output and the power in its 2nd harmonic level at the output.
THIRD HARMONIC DISTORTION (3RD HARM) is the difference, expressed in dB, between the RMS power in
the input frequency at the output and the power in its 3rd harmonic level at the output.
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Timing Diagrams
tDP
tDP
OUTCLK
tHO
tSUO
SData
Valid Data
Valid Data
Valid Data
Figure 3. Serial Output Data Timing
Sample
N+1
Sample
N
VINA
Sample
N+2
VINB
tSAMPLE = 1/fCLK
CLK
tSD
tDP = tSAMPLE/12
OUTCLK
tFP = tSAMPLE
Sample N-1
ORA,
ORB
D0
D11
D0
D11
D2
D1
D3
D4
D5
D6
D7
D8
D9
D10
D0
SD1_A,
SD1_B
D11
FRAME
Sample N
Sample N+1
Sample N
Sample N+1
Figure 4. Serial Output Data Format in Single-Lane Mode
14
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Sample N+1
Sample
N
VINA
Sample
N+2
VINB
tSAMPLE = 1/fCLK
CLK
tSD
tDP = tSAMPLE/6
OUTCLK
tFP = 2 x tSAMPLE
FRAME
OFFSET MODE :
tDP
Sample N
Sample N-2
SD1_A,
SD1_B
D1
D0
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
Sample N-1
SD0_A,
SD0_B
D7
D6
D5
D0
D11
D10
D9
D4
D3
Sample N+1
D4
ORA,
ORB
D3
D2
D1
D0
D11
D10
Sample N
D9
D8
D7
D6
D5
Sample N+1
WORD-ALIGNED MODE :
SD1_A,
SD1_B
D1
D0
D11
D10
D9
D8
D7
Sample N-1
SD0_A,
SD0_B
D1
Sample
N+2
Sample N
Sample N-2
D6
D5
D4
D3
D2
D1
D0
D11
D10
Sample
N+3
Sample N+1
D0
D11
D10
ORA,
ORB
D9
D8
Sample N
D7
D6
D5
D9
D4
D3
D2
D1
D0
D11
D10
D9
Sample N+1
Figure 5. Serial Output Data Format in Dual-Lane Mode
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Transfer Characteristic
Figure 6. Transfer Characteristic
Typical Performance Characteristics DNL, INL
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, 50% Duty Cycle, DCS disabled, VCM = VCMO, TA = 25°C.
16
DNL
INL
Figure 7.
Figure 8.
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Typical Performance Characteristics
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, 50% Duty Cycle, DCS disabled, VCM = VCMO, fIN = 10 MHz, TA = 25°C.
SNR, SINAD, SFDR vs. VA
Distortion vs. VA
Figure 9.
Figure 10.
SNR, SINAD, SFDR vs. Clock Duty Cycle
Distortion vs. Clock Duty Cycle
Figure 11.
Figure 12.
SNR, SINAD, SFDR vs. Clock Duty Cycle, DCS Enabled
Distortion vs. Clock Duty Cycle, DCS Enabled
Figure 13.
Figure 14.
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Typical Performance Characteristics (continued)
Unless otherwise specified, the following specifications apply: AGND = DRGND = 0V, VA = +3.3V, VDR = +3.0V, Internal VREF
= +1.2V, fCLK = 105 MHz, 50% Duty Cycle, DCS disabled, VCM = VCMO, fIN = 10 MHz, TA = 25°C.
18
Spectral Response @ 10 MHz Input
Spectral Response @ 70 MHz Input
Figure 15.
Figure 16.
Spectral Response @ 240 MHz Input
IMD, fIN1 = 20 MHz, fIN2 = 21 MHz
Figure 17.
Figure 18.
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FUNCTIONAL DESCRIPTION
Operating on a single +3.3V supply, the ADC12DS105 digitizes two differential analog input signals to 12 bits,
using a differential pipelined architecture with error correction circuitry and an on-chip sample-and-hold circuit to
ensure maximum performance. The user has the choice of using an internal 1.2V stable reference, or using an
external 1.2V reference. Any external reference is buffered on-chip to ease the task of driving that pin. Duty cycle
stabilization and output data format are selectable using the quad state function OF/DCS pin (pin 19). The output
data can be set for offset binary or two's complement.
Applications Information
OPERATING CONDITIONS
We recommend that the following conditions be observed for operation of the ADC12DS105:
2.7V ≤ VA ≤ 3.6V
2.7V ≤ VDR ≤ VA
25 MHz ≤ fCLK ≤ 105 MHz
1.2V internal reference
VREF = 1.2V (for an external reference)
VCM = 1.5V (from VCMO)
ANALOG INPUTS
Signal Inputs
Differential Analog Input Pins
The ADC12DS105 has a pair of analog signal input pins for each of two channels. VIN+ and VIN− form a
differential input pair. The input signal, VIN, is defined as
VIN = (VIN+) – (VIN−)
(4)
Figure 19 shows the expected input signal range. Note that the common mode input voltage, VCM, should be
1.5V. Using VCMO (pins 7,9) for VCM will ensure the proper input common mode level for the analog input signal.
The positive peaks of the individual input signals should each never exceed 2.6V. Each analog input pin of the
differential pair should have a maximum peak-to-peak voltage of 1V, be 180° out of phase with each other and
be centered around VCM.The peak-to-peak voltage swing at each analog input pin should not exceed the 1V or
the output data will be clipped.
Figure 19. Expected Input Signal Range
For single frequency sine waves the full scale error in LSB can be described as approximately
EFS = 4096 ( 1 - sin (90° + dev))
(5)
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Where dev is the angular difference in degrees between the two signals having a 180° relative phase relationship
to each other (see Figure 20). For single frequency inputs, angular errors result in a reduction of the effective full
scale input. For complex waveforms, however, angular errors will result in distortion.
Figure 20. Angular Errors Between the Two Input Signals Will Reduce the Output Level or Cause
Distortion
It is recommended to drive the analog inputs with a source impedance less than 100Ω. Matching the source
impedance for the differential inputs will improve even ordered harmonic performance (particularly second
harmonic).
Table 1 indicates the input to output relationship of the ADC12DS105.
Table 1. Input to Output Relationship
VIN+
VIN−
Binary Output
2’s Complement Output
VCM − VREF/2
VCM + VREF/2
0000 0000 0000
1000 0000 0000
VCM − VREF/4
VCM + VREF/4
0100 0000 0000
1100 0000 0000
VCM
VCM
1000 0000 0000
0000 0000 0000
VCM + VREF/4
VCM − VREF/4
1100 0000 0000
0100 0000 0000
VCM + VREF/2
VCM − VREF/2
1111 1111 1111
0111 1111 1111
Negative Full-Scale
Mid-Scale
Positive Full-Scale
Driving the Analog Inputs
The VIN+ and the VIN− inputs of the ADC12DS105 have an internal sample-and-hold circuit which consists of an
analog switch followed by a switched-capacitor amplifier.
Figure 21 and Figure 22 show examples of single-ended to differential conversion circuits. The circuit in
Figure 21 works well for input frequencies up to approximately 70MHz, while the circuit in Figure 22 works well
above 70MHz.
VIN
0.1 PF
20:
ADT1-1WT
18 pF
50:
ADC
Input
0.1 PF
0.1 PF
20:
VCMO
Figure 21. Low Input Frequency Transformer Drive Circuit
VIN
0.1 PF
ETC1-1-13
100:
3 pF
0.1 PF
ADC
Input
100:
ETC1-1-13
VCMO
0.1 PF
Figure 22. High Input Frequency Transformer Drive Circuit
20
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One short-coming of using a transformer to achieve the single-ended to differential conversion is that most RF
transformers have poor low frequency performance. A differential amplifier can be used to drive the analog inputs
for low frequency applications. The amplifier must be fast enough to settle from the charging glitches on the
analog input resulting from the sample-and-hold operation before the clock goes high and the sample is passed
to the ADC core.
Input Common Mode Voltage
The input common mode voltage, VCM, should be in the range of 1.4V to 1.6V and be a value such that the peak
excursions of the analog signal do not go more negative than ground or more positive than 2.6V. It is
recommended to use VCMO (pins 7,9) as the input common mode voltage.
Reference Pins
The ADC12DS105 is designed to operate with an
reference is the default condition when no external
applied to the VREF pin, then that voltage is used for
ground with a 0.1 µF capacitor close to the reference
internal or external 1.2V reference. The internal 1.2 Volt
reference input is applied to the VREF pin. If a voltage is
the reference. The VREF pin should always be bypassed to
input pin.
It is important that all grounds associated with the reference voltage and the analog input signal make connection
to the ground plane at a single, quiet point to minimize the effects of noise currents in the ground path.
The Reference Bypass Pins (VRP, VCMO, and VRN) for channels A and B are made available for bypass purposes.
These pins should each be bypassed to AGND with a low ESL (equivalent series inductance) 1 µF capacitor
placed very close to the pin to minimize stray inductance. A 0.1 µF capacitor should be placed between VRP and
VRN as close to the pins as possible, and a 1 µF capacitor should be placed in parallel. This configuration is
shown in Figure 23. It is necessary to avoid reference oscillation, which could result in reduced SFDR and/or
SNR. VCMO may be loaded to 1mA for use as a temperature stable 1.5V reference. The remaining pins should
not be loaded.
Smaller capacitor values than those specified will allow faster recovery from the power down mode, but may
result in degraded noise performance. Loading any of these pins, other than VCMO may result in performance
degradation.
The nominal voltages for the reference bypass pins are as follows:
VCMO = 1.5 V
VRP = 2.0 V
VRN = 1.0 V
OF/DCS Pin
Duty cycle stabilization and output data format are selectable using this quad state function pin. When enabled,
duty cycle stabilization can compensate for clock inputs with duty cycles ranging from 30% to 70% and generate
a stable internal clock, improving the performance of the part. With OF/DCS = VA the output data format is 2's
complement and duty cycle stabilization is not used. With OF/DCS = AGND the output data format is offset
binary and duty cycle stabilization is not used. With OF/DCS = (2/3)*VA the output data format is 2's complement
and duty cycle stabilization is applied to the clock. If OF/DCS is (1/3)*VA the output data format is offset binary
and duty cycle stabilization is applied to the clock. While the sense of this pin may be changed "on the fly," doing
this is not recommended as the output data could be erroneous for a few clock cycles after this change is made.
Note: This signal has no effect when SPI_EN is high and the serial control interface is enabled.
DIGITAL INPUTS
Digital CMOS compatible inputs consist of CLK, and PD_A, PD_B, Reset_DLL, DLC, TEST, WAM, SPI_EN,
SCSb, SCLK, and SDI.
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Clock Input
The CLK controls the timing of the sampling process. To achieve the optimum noise performance, the clock input
should be driven with a stable, low jitter clock signal in the range indicated in the Electrical Table. The clock input
signal should also have a short transition region. This can be achieved by passing a low-jitter sinusoidal clock
source through a high speed buffer gate. The trace carrying the clock signal should be as short as possible and
should not cross any other signal line, analog or digital, not even at 90°.
The clock signal also drives an internal state machine. If the clock is interrupted, or its frequency is too low, the
charge on the internal capacitors can dissipate to the point where the accuracy of the output data will degrade.
This is what limits the minimum sample rate.
The clock line should be terminated at its source in the characteristic impedance of that line. Take care to
maintain a constant clock line impedance throughout the length of the line. Refer to Application Note SNLS035
for information on setting characteristic impedance.
It is highly desirable that the the source driving the ADC clock pins only drive that pin. However, if that source is
used to drive other devices, then each driven pin should be AC terminated with a series RC to ground, such that
the resistor value is equal to the characteristic impedance of the clock line and the capacitor value is
(6)
where tPD is the signal propagation rate down the clock line, "L" is the line length and ZO is the characteristic
impedance of the clock line. This termination should be as close as possible to the ADC clock pin but beyond it
as seen from the clock source. Typical tPD is about 150 ps/inch (60 ps/cm) on FR-4 board material. The units of
"L" and tPD should be the same (inches or centimeters).
The duty cycle of the clock signal can affect the performance of the A/D Converter. Because achieving a precise
duty cycle is difficult, the ADC12DS105 has a Duty Cycle Stabilizer.
Power-Down (PD_A and PD_B)
The PD_A and PD_B pins, when high, hold the respective channel of the ADC12DS105 in a power-down mode
to conserve power when that channel is not being used. The channels may be powered down individually or
together. The data in the pipeline is corrupted while in the power down mode.
The Power Down Mode Exit Cycle time is determined by the value of the components on the reference bypass
pins ( VRP, VCMO and VRN ). These capacitors lose their charge in the Power Down mode and must be recharged
by on-chip circuitry before conversions can be accurate. Smaller capacitor values allow slightly faster recovery
from the power down mode, but can result in a reduction in SNR, SINAD and ENOB performance.
Note: This signal has no effect when SPI_EN is high and the serial control interface is enabled.
Reset_DLL
This pin is normally low. If the input clock frequency is changed abruptly, the internal timing circuits may become
unlocked. Cycle this pin high for 1 microsecond to re-lock the DLL. The DLL will lock in several microseconds
after Reset_DLL is asserted.
DLC
This pin sets the output data configuration. With this signal at logic-1, all data is sourced on a single lane
(SD1_x) for each channel. When this signal is at logic-0, the data is sourced on dual lanes (SD0_x and SD1_x)
for each channel. This simplifies data capture at higher data rates.
Note: This signal has no effect when SPI_EN is high and the SPI interface is enabled.
TEST
When this signal is asserted high, a fixed test pattern (101001100011 msb->lsb) is sourced at the data outputs.
When low, the ADC is in normal operation. The user may specify a custom test pattern via the serial control
interface.
Note: This signal has no effect when SPI_EN is high and the SPI interface is enabled.
22
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WAM
In dual-lane mode only, when this signal is at logic-0 the serial data words are offset by half-word. With this
signal at logic-1 the serial data words are aligned with each other. In single lane mode this pin must be set to
logic-0.
Note: This signal has no effect when SPI_EN is high and the SPI interface is enabled.
SPI_EN
The SPI interface is enabled when this signal is asserted high. In this case the direct control pins (OF/DCS,
PD_A, PD_B, DLC, WAM, TEST) have no effect. When this signal is deasserted, the SPI interface is disabled
and the direct control pins are enabled.
SCSb, SDI, SCLK
These pins are part of the SPI interface. See Serial Control Interface for more information.
DIGITAL OUTPUTS
Digital outputs consist of six LVDS signal pairs (SD0_A, SD1_A, SD0_B, SD1_B, OUTCLK, FRAME) and CMOS
logic outputs ORA, ORB, DLL_Lock, and SDO.
LVDS Outputs
The digital data for each channel is provided in a serial format. Two modes of operation are available for the
serial data format. Single-lane serial format (shown in Figure 4) uses one set of differential data signals per
channel. Dual-lane serial format (shown in Figure 5) uses two sets of differential data signals per channel in
order to slow down the data and clock frequency by a factor of 2. At slower rates of operation (typically below 65
MSPS) the single-lane mode may be the most efficient to use. At higher rates the user may want to employ the
dual-lane scheme. In either case DDR-type clocking is used. For each data channel, an overrange indication is
also provided. The OR signal is updated with each frame of data.
ORA, ORB
These CMOS outputs are asserted logic-high when their respective channel’s data output is out-of-range in
either high or low direction.
DLL_Lock
When the internal DLL is locked to the input CLK, this pin outputs a logic high. If the input CLK is changed
abruptly, the internal DLL may become unlocked and this pin will output a logic low. Cycle Reset_DLL to re-lock
the DLL to the input CLK.
SDO
This pin is part of the SPI interface. See Serial Control Interface for more information.
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+3.3V
+3.0V
3x 0.1 PF
5x 0.1 PF
+
0.1 PF
59
7
0.1 PF
0.1 PF
0.1 PF
1 PF
5 V A
RP
6
VRNA
11
0.1 PF 10
20
0.1 PF
SDO
0.1 PF
1 PF
VCMOB
0.1 PF
2
VINA+
VINA-
OUTCLK+
OUTCLK-
50
FRAME+
FRAME-
0.1 PF
2
20
45
44
43
42
SD1_A+ 38
SD1_A- 37
18 pF
0.1 PF
55
13
14
To capture device (ASIC or FPGA).
Note, all signal pairs should be routed with
100 ohm differential impedance, and should
be terminated with a 100 ohm resistor near
the input of the capture device.
SD0_A+ 36
SD0_A- 35
VINB+
VINB-
SD1_B+ 34
ADT1-1WT
Crystal Oscillator
19
57
20
These control pins are
ignored when SPI_EN is high
27
47
SPI_EN
56
SD1_B- 33
SD0_B+ 32
SD0_B- 31
CLK
OF/DCS
PD_A
PD_B
TEST
LVDS_Bias
29
3.6k
WAM
SPI_EN
1
AGND
4
AGND
12
AGND
15
AGND
18
25
DR GND
39
DR GND
51
DR GND
1
20
0.1 PF
SPI Interface
54
ADC12DS105
3
2
ADT1-1WT
VIN_B
53
VRNB
18 pF
20
SCSb
52
VRPB
0.1 PF
0.1 PF
SCLK
SDI
9
0.1 PF
1
VREF
VCMOA
0.1 PF
50
VIN_A
VDR 26
VDR 40
VDR 50
VA
VA
VA
VA
VA
8
16
17
58
60
10 PF
Figure 23. Application Circuit
Serial Control Interface
The ADC12DS105 has a serial interface that allows access to the control registers. The serial interface is a
generic 4-wire synchronous interface that is compatible with SPI type interfaces that are used on many
microcontrollers and DSP controllers.
The ADC's input clock must be running for the Serial Control Interface to operate. It is enabled when the SPI_EN
(pin 56) signal is asserted high. In this case the direct control pins (OF/DCS, PD_A, PD_B, DLC, WAM, TEST)
have no effect. When this signal is deasserted, the SPI interface is disabled and the direct control pins are
enabled.
Each serial interface access cycle is exactly 16 bits long. Figure 24 shows the access protocol used by this
interface. Each signal's function is described below. The Read Timing is shown in Figure 25, while the Write
Timing is shown in Figure 26
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
D2
D1
D0
(LSB)
D2
D1
17
SCLK
SCSb
COMMAND FIELD
SDI
C7
C6
C5
C4
R/Wb
0
0
0
Reserved (3-bits)
DATA FIELD
C3
C2
C1
C0
A3
A2
A1
A0
D7
D6
(MSB)
D5
D4
D3
Write DATA
Address (4-bits)
D7
D6
(MSB)
D5
D4
D3
D0
(LSB)
Hi-Z
Read DATA
SDO
Data (8-bits)
Single Access Cycle
Figure 24. Serial Interface Protocol
SCLK: Used to register the input data (SDI) on the rising edge; and to source the output data (SDO) on the
falling edge. User may disable clock and hold it in the low-state, as long as clock pulse-width min spec is not
violated when clock is enabled or disabled.
SCSb: Serial Interface Chip Select. Each assertion starts a new register access - that is, the SDATA field
protocol is required. The user is required to deassert this signal after the 16th clock. If the SCSb is deasserted
before the 16th clock, no address or data write will occur. The rising edge captures the address just shifted-in
and, in the case of a write operation, writes the addressed register. There is a minimum pulse-width requirement
for the deasserted pulse - which is specified in the Electrical Specifications section.
SDI: Serial Data. Must observe setup/hold requirements with respect to the SCLK. Each cycle is 16-bits long.
R/Wb:
A value of '1' indicates a read operation, while a value of '0' indicates
a write operation.
Reserved:
Reserved for future use. Must be set to 0.
ADDR:
Up to 3 registers can be addressed.
DATA:
In a write operation the value in this field will be written to the
register addressed in this cycle when SCSb is deasserted. In a read
operation this field is ignored.
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SDO: This output is normally at TRI-STATE and is driven only when SCSb is asserted. Upon SCSb assertion,
contents of the register addressed during the first byte are shifted out with the second 8 SCLK falling edges.
Upon power-up, the default register address is 00h.
st
th
th
1 clock
16
8 clock
clock
SCLK
tCSH
tCSS
tCSH
tCSS
CSb
tOZD
SDO
tODZ
tOD
D7
D1
D0
Figure 25. Read Timing
tPL
tPH
16th clock
SCLK
tSU
SDI
tH
Valid Data
Valid Data
Figure 26. Write Timing
Table 2. Device Control Register, Address 0h
7
6
OM
5
4
3
2
1
0
DLC
DCS
OF
WAM
PD_A
PD_B
Reset State : 08h
Bits (7:6)
Operational Mode
0 0 Normal Operation.
0 1 Test Output mode. A fixed test pattern (1010011000111msb->lsb) is sourced at the data outputs.
1 0 Test Output mode. Data pattern defined by user in registers 01h and 02h is sourced at data outputs.
1 1 Reserved.
Bit 5
Data Lane Configuration. When this bit is set to '0', the serial data interface is configured for dual-lane mode where the
data words are output on two data outputs (SD1 and SD0) at half the rate of the single-lane interface. When this bit is
set to ‘1’, serial data is output on the SD1 output only and the SD0 outputs are held in a high-impedance state
Bit 4
Duty Cycle Stabilizer. When this bit is set to '0' the DCS is off. When this bit is set to ‘1’, the DCS is on.
Bit 3
Output Data Format. When this bit is set to ‘1’ the data output is in the “twos complement” form. When this bit is set to
‘0’ the data output is in the “offset binary” form.
Bit 2
Word Alignment Mode.
This bit must be set to '0' in the single-lane mode of operation.
In dual-lane mode, when this bit is set to '0' the serial data words are offset by half-word. This gives the least latency
through the device. When this bit is set to '1' the serial data words are in word-aligned mode. In this mode the serial
data on the SD1 lane is additionally delayed by one CLK cycle. (Refer to Figure 5).
Bit 1
Power-Down Channel A. When this bit is set to '1', Channel A is in power-down state and Normal operation is
suspended.
Bit 0
Power-Down Channel B. When this bit is set to '1', Channel B is in power-down state and Normal operation is
suspended.
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Table 3. User Test Pattern Register 0, Address 1h
7
6
5
4
Reserved
3
2
1
0
User Test Pattern (13:6)
Reset State : 00h
Bits (7:6)
Reserved. Must be set to '0'.
Bits (5:0)
User Test Pattern. Most-significant 6 bits of the 12-bit pattern that will be sourced out of the data outputs in Test
Output Mode.
Table 4. User Test Pattern Register 1, Address 2h
7
6
5
4
3
User Test Pattern (5:0)
2
1
0
Reserved
Reset State : 00h
Bits (7:2)
User Test Pattern. Least-significant 6 bits of the 12-bit pattern that will be sourced out of the data outputs in Test
Output Mode.
Bits (1:0)
Reserved. Must be set to '0'.
POWER SUPPLY CONSIDERATIONS
The power supply pins should be bypassed with a 0.1 µF capacitor and with a 100 pF ceramic chip capacitor
close to each power pin. Leadless chip capacitors are preferred because they have low series inductance.
As is the case with all high-speed converters, the ADC12DS105 is sensitive to power supply noise. Accordingly,
the noise on the analog supply pin should be kept below 100 mVP-P.
No pin should ever have a voltage on it that is in excess of the supply voltages, not even on a transient basis. Be
especially careful of this during power turn on and turn off.
LAYOUT AND GROUNDING
Proper grounding and proper routing of all signals are essential to ensure accurate conversion. Maintaining
separate analog and digital areas of the board, with the ADC12DS105 between these areas, is required to
achieve specified performance.
Capacitive coupling between the typically noisy digital circuitry and the sensitive analog circuitry can lead to poor
performance. The solution is to keep the analog circuitry separated from the digital circuitry, and to keep the
clock line as short as possible.
Since digital switching transients are composed largely of high frequency components, total ground plane copper
weight will have little effect upon the logic-generated noise. This is because of the skin effect. Total surface area
is more important than is total ground plane area.
Generally, analog and digital lines should cross each other at 90° to avoid crosstalk. To maximize accuracy in
high speed, high resolution systems, however, avoid crossing analog and digital lines altogether. It is important to
keep clock lines as short as possible and isolated from ALL other lines, including other digital lines. Even the
generally accepted 90° crossing should be avoided with the clock line as even a little coupling can cause
problems at high frequencies. This is because other lines can introduce jitter into the clock line, which can lead to
degradation of SNR. Also, the high speed clock can introduce noise into the analog chain.
Best performance at high frequencies and at high resolution is obtained with a straight signal path. That is, the
signal path through all components should form a straight line wherever possible.
Be especially careful with the layout of inductors and transformers. Mutual inductance can change the
characteristics of the circuit in which they are used. Inductors and transformers should not be placed side by
side, even with just a small part of their bodies beside each other. For instance, place transformers for the analog
input and the clock input at 90° to one another to avoid magnetic coupling.
The analog input should be isolated from noisy signal traces to avoid coupling of spurious signals into the input.
Any external component (e.g., a filter capacitor) connected between the converter's input pins and ground or to
the reference input pin and ground should be connected to a very clean point in the ground plane.
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All analog circuitry (input amplifiers, filters, reference components, etc.) should be placed in the analog area of
the board. All digital circuitry and dynamic I/O lines should be placed in the digital area of the board. The
ADC12DS105 should be between these two areas. Furthermore, all components in the reference circuitry and
the input signal chain that are connected to ground should be connected together with short traces and enter the
ground plane at a single, quiet point. All ground connections should have a low inductance path to ground.
DYNAMIC PERFORMANCE
To achieve the best dynamic performance, the clock source driving the CLK input must have a sharp transition
region and be free of jitter. Isolate the ADC clock from any digital circuitry with buffers, as with the clock tree
shown in Figure 27. The gates used in the clock tree must be capable of operating at frequencies much higher
than those used if added jitter is to be prevented.
As mentioned inLAYOUT AND GROUNDING, it is good practice to keep the ADC clock line as short as possible
and to keep it well away from any other signals. Other signals can introduce jitter into the clock signal, which can
lead to reduced SNR performance, and the clock can introduce noise into other lines. Even lines with 90°
crossings have capacitive coupling, so try to avoid even these 90° crossings of the clock line.
Figure 27. Isolating the ADC Clock from other Circuitry with a Clock Tree
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REVISION HISTORY
Changes from Revision D (April 2013) to Revision E
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 28
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
ADC12DS105CISQ/NOPB
ACTIVE
WQFN
NKA
60
2000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
12DS105
ADC12DS105CISQE/NOPB
ACTIVE
WQFN
NKA
60
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
12DS105
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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