LMV721_06

LMV721/LMV722 10MHz, Low Noise, Low Voltage, and Low Power Operational Amplifier June 2006 LMV721/LMV722 10MHz, Low Noise, Low Voltage, and Low Power Operational Amplifier General Description The LMV721 (Single) and LMV722 (Dual) are low noise, low voltage, and low power op amps, that can be designed into a wide range of applications. The LMV721/LMV722 has a unity gain bandwidth of 10MHz, a slew rate of 5V/us, and a quiescent current of 930uA/amplifier at 2.2V. The LMV721/722 are designed to provide optimal performance in low voltage and low noise systems. They provide rail-to-rail output swing into heavy loads. The input commonmode voltage range includes ground, and the maximum input offset voltage are 3.5mV (Over Temp.) for the LMV721/ LMV722. Their capacitive load capability is also good at low supply voltages. The operating range is from 2.2V to 5.5V. The chip is built with National’s advanced Submicron SiliconGate BiCMOS process. The single version, LMV721, is available in 5 pin SOT23-5 and a SC-70 (new) package. The dual version, LMV722, is available in a SO-8, MSOP-8 and 8-pin LLP package. Features (For Typical, 5 V Supply Values; Unless Otherwise Noted) n Guaranteed 2.2V and 5.0V Performance n Low Supply Current LMV721/2 930µA/amplifier @2.2V n High Unity-Gain Bandwidth 10MHz n Rail-to-Rail Output Swing @ 600Ω load 120mV from either rail at 2.2V @ 2kΩ load 50mV from either rail at 2.2V n Input Common Mode Voltage Range Includes Ground n Silicon Dust™, SC70-5 Package 2.0x2.0x1.0 mm n Miniature packaging: LLP-8 2.5mm x 3mm x 0.8mm n Input Voltage Noise Applications n n n n Cellular an Cordless Phones Active Filter and Buffers Laptops and PDAs Battery Powered Electronics Typical Application A Battery Powered Microphone Preamplifier 10092244 Silicon Dust™ is a trademark of National Semiconductor Corporation. © 2006 National Semiconductor Corporation DS100922 www.national.com LMV721/LMV722 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Human Body Model Machine Model Differential Input Voltage Supply Voltage (V+ – V−) Soldering Information Infrared or Convection (20 sec.) Storage Temp. Range Junction Temperature (Note 4) 235˚C −65˚C to 150˚C 150˚C 2000V 100V Operating Ratings (Note 3) Supply Voltage Temperature Range Thermal Resistance (θJA) Silicon Dust SC70-5 Pkg Tiny SOT23-5 Pkg SO Pkg, 8-pin Surface Mount MSOP Pkg, 8-Pin Mini Surface Mount SO Pkg, 14-Pin Surface Mount LLP pkg, 8-Pin 440˚C/W 265 ˚C/W 190˚C/W 235 ˚C/W 145˚C/W 58.2˚C/W 2.2V to 5.0V −40˚C ≤T J ≤85˚C ± Supply Voltage 5.5V 2.2V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.2V, V− = 0V, VCM = V+/2, VO = V+/2 and R Boldface limits apply at the temperature extremes. Symbol VOS TCVOS IB IOS CMRR PSRR VCM AV Parameter Input Offset Voltage Input Offset Voltage Average Drift Input Bias Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio Input Common-Mode Voltage Range Large Signal Voltage Gain 0V ≤ VCM ≤ 1.3V 2.2V ≤ V+ ≤ 5V, VO = 0 VCM = 0 For CMRR ≥ 50dB RL=600Ω VO = 0.75V to 2.00V RL= 2kΩ VO = 0.50V to 2.10V VO Output Swing RL = 600Ω to V+/2 Condition Typ (Note 5) 0.02 0.6 260 25 88 90 −0.30 1.3 81 84 2.125 0.071 RL = 2kΩ to V+/2 2.177 0.056 IO Output Current Sourcing, VO = 0V VIN(diff) = ± 0.5V Sinking, VO = 2.2V VIN(diff) = ± 0.5V IS Supply Current LMV721 LMV722 14.9 17.6 0.93 1.81 75 60 75 60 2.090 2.065 0.120 0.145 2.150 2.125 0.080 0.105 10.0 5.0 10.0 5.0 1.2 1.5 2.2 2.6 70 64 70 64 Limit (Note 6) 3 3.5 L > 1 MΩ. Units mV max µV/˚C nA nA dB min dB min V V dB min dB min V min V max V min V max mA min mA min mA max www.national.com 2 LMV721/LMV722 2.2V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.2V, V− = 0V, VCM = V+/2, VO = V+/2 and R Boldface limits apply at the temperature extremes. Symbol SR GBW Φm Gm en in THD Slew Rate Gain-Bandwidth Product Phase Margin Gain Margin Input-Referred Voltage Noise Input-Referred Current Noise Total Harmonic Distortion f = 1 kHz f = 1 kHz f = 1 kHz AV = 1 RL = 600Ω, VO = 500 mVPP Parameter (Note 7) Conditions Typ (Note 5) 4.9 10 67.4 −9.8 9 0.3 L > 1 MΩ. Units V/µs MHz Deg dB 0.004 % 5V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V− = 0V, VCM = V+/2, VO = V+/2 and RL > 1 MΩ. Boldface limits apply at the temperature extremes. Symbol VOS TCVOS IB IOS CMRR PSRR VCM AV Parameter Input Offset Voltage Input Offset Voltage Average Drift Input Bias Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio Input Common-Mode Voltage Range Large Signal Voltage Gain 0V ≤ VCM ≤ 4.1V 2.2V ≤ V+ ≤ 5.0V, VO = 0 VCM = 0 For CMRR ≥ 50dB RL = 600Ω VO = 0.75V to 4.80V RL = 2kΩ, VO = 0.70V to 4.90V, VO Output Swing RL = 600Ω to V+/2 Condition Typ (Note 5) −0.08 0.6 260 25 89 90 −0.30 4.1 87 94 4.882 0.134 RL = 2kΩ to V+/2 4.952 0.076 IO Output Current Sourcing, VO = 0V VIN(diff) = ± 0.5V Sinking, VO = 5V VIN(diff) = ± 0.5V IS Supply Current LMV721 LMV722 52.6 23.7 1.03 2.01 80 70 85 70 4.840 4.815 0.190 0.215 4.930 4.905 0.110 0.135 25.0 12.0 15.0 8.5 1.4 1.7 2.4 2.8 70 64 70 64 Limit (Note 6) 3 3.5 Units mV max µV/˚C nA nA dB min dB min V V dB min dB min V min V max V min V max mA min mA min mA max 3 www.national.com LMV721/LMV722 5V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V− = 0V, VCM = V+/2, VO = V+/2 and R Boldface limits apply at the temperature extremes. Symbol SR GBW Φm Gm en in THD Slew Rate Gain-Bandwidth Product Phase Margin Gain Margin Input-Related Voltage Noise Input-Referred Current Noise Total Harmonic Distortion f = 1 kHz f = 1 kHz f = 1kHz, AV = 1 RL = 600Ω, VO = 1 VPP Parameter (Note 7) Conditions Typ (Note 5) 5.25 10.0 72 −11 8.5 0.2 L > 1 MΩ. Units V/µs MHz Deg dB 0.001 % Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics. Note 2: Human body model, 1.5 kΩ in series with 100 pF. Machine model, 200Ω in series with 100 pF. Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150˚C. Output currents in excess of 30 mA over long term may adversely affect reliability. Note 4: The maximum power dissipation is a function of TJ(max), θJA, and TA . The maximum allowable power dissipation at any ambient temperature is P D = (TJ(max)–T A)/θJA. All numbers apply for packages soldered directly into a PC board. Note 5: Typical Values represent the most likely parametric norm. Note 6: All limits are guaranteed by testing or statistical analysis. Note 7: Connected as voltage follower with 1V step input. Number specified is the slower of the positive and negative slew rate. www.national.com 4 LMV721/LMV722 Typical Performance Characteristics Supply Current vs. Supply Voltage (LMV721) Sourcing Current vs. Output Voltage (VS = 2.2V) 10092201 10092202 Sourcing Current vs. Output Voltage (VS = 5V) Sinking Current vs. Output Voltage (VS = 2.2V) 10092203 10092204 Sinking Current vs. Output Voltage (VS = 5V) Output Voltage Swing vs. Supply Voltage (RL = 600Ω) 10092205 10092206 5 www.national.com LMV721/LMV722 Typical Performance Characteristics Output Voltage Swing vs. Suppy Voltage (RL = 2kΩ) (Continued) Input Offset Voltage vs. Input Common-Mode Voltage Range VS = 2.2V 10092207 10092208 Input Offset Voltage vs. Input Common-Mode Voltage Range VS = 5V Input Offset Voltage vs. Supply Voltage (VCM = V+/2) 10092209 10092210 Input Voltage vs. Output Voltage (VS = 2.2V, RL = 2kΩ) Input Voltage vs. Output Voltage (VS = 5V, RL = 2kΩ) 10092211 10092212 www.national.com 6 LMV721/LMV722 Typical Performance Characteristics Input Voltage Noise vs. Frequency (Continued) Input Current Noise vs. Frequency 10092238 10092232 +PSRR vs. Frequency −PSRR vs. Frequency 10092213 10092214 CMRR vs. Frequency Gain and Phase Margin vs. Frequency (VS = 2.2V, RL 600Ω) 10092245 10092215 7 www.national.com LMV721/LMV722 Typical Performance Characteristics Gain and Phase Margin vs. Frequency (VS = 5V, RL 600Ω) (Continued) Slew Rate vs. Supply Voltage 10092216 10092217 THD vs. Frequency 10092242 www.national.com 8 LMV721/LMV722 Application Notes 1.0 BENEFITS OF THE LMV721/722 SIZE The small footprints of the LMV721/722 packages save space on printed circuit boards, and enable the design of smaller electronic products, such as cellular phones, pagers, or other portable systems. The low profile of the LMV721/ 722 make them possible to use in PCMCIA type III cards. Signal Integrity. Signals can pick up noise between the signal source and the amplifier. By using a physically smaller amplifier package, the LMV721/722 can be placed closer to the signal source, reducing noise pickup and increasing signal integrity. Simplified Board Layout. These products help you to avoid using long pc traces in your pc board layout. This means that no additional components, such as capacitors and resistors, are needed to filter out the unwanted signals due to the interference between the long pc traces. Low Supply Current. These devices will help you to maximize battery life. They are ideal for battery powered systems. Low Supply Voltage. National provides guaranteed performance at 2.2V and 5V. These guarantees ensure operation throughout the battery lifetime. Rail-to-Rail Output. Rail-to-rail output swing provides maximum possible dynamic range at the output. This is particularly important when operating on low supply voltages. Input Includes Ground. Allows direct sensing near GND in single supply operation. Protection should be provided to prevent the input voltages from going negative more than −0.3V (at 25˚C). An input clamp diode with a resistor to the IC input terminal can be used. 2.0 CAPACITIVE LOAD TOLERANCE The LMV721/722 can directly drive 4700pF in unity-gain without oscillation. The unity-gain follower is the most sensitive configuration to capacitive loading. Direct capacitive loading reduces the phase margin of amplifiers. The combination of the amplifier’s output impedance and the capacitive load induces phase lag. This results in either an underdamped pulse response or oscillation. To drive a heavier capacitive load, circuit in Figure 1 can be used. 10092231 FIGURE 2. Pulse Response of the LMV721 Circuit in Figure 1 The circuit in Figure 3 is an improvement to the one in Figure 1 because it provides DC accuracy as well as AC stability. If there were a load resistor in Figure 1, the output would be voltage divided by RISO and the load resistor. Instead, in Figure 3, RF provides the DC accuracy by using feedforward techniques to connect VIN to RL. Caution is needed in choosing the value of RF due to the input bias current of the LMV721/722. CF and RISO serve to counteract the loss of phase margin by feeding the high frequency component of the output signal back to the amplifier’s inverting input, thereby preserving phase margin in the overall feedback loop. Increased capacitive drive is possible by increasing the value of CF. This in turn will slow down the pulse response. 10092219 FIGURE 3. Indirectly Driving A Capacitive Load with DC Accuracy 3.0 INPUT BIAS CURRENT CANCELLATION The LMV721/722 family has a bipolar input stage. The typical input bias current of LMV721/722 is 260nA with 5V supply. Thus a 100kΩ input resistor will cause 26mV of error voltage. By balancing the resistor values at both inverting and non-inverting inputs, the error caused by the amplifier’s input bias current will be reduced. The circuit in Figure 4 shows how to cancel the error caused by input bias current. 10092218 FIGURE 1. Indirectly Driving A capacitive Load Using Resistive Isolation In Figure 1, the isolation resistor RISO and the load capacitor CL form a pole to increase stability by adding more phase margin to the overall system. the desired performance depends on the value of RISO. The bigger the RISO resistor value, the more stable VOUT will be. Figure 2 is an output waveform of Figure 1 using 100kΩ for RISO and 2000µF for C L. 9 www.national.com LMV721/LMV722 Application Notes (Continued) 4.2.1 Three-op-amp Instrumentation Amplifier The LMV721/722 can be used to build a three-op-amp instrumentation amplifier as shown in Figure 6 10092220 FIGURE 4. Cancelling the Error Caused by Input Bias Current 10092230 4.0 TYPICAL SINGLE-SUPPLY APPLICATION CIRCUITS 4.1 Difference Amplifier The difference amplifier allows the subtraction of two voltages or, as a special case, the cancellation of a signal common to two inputs. It is useful as a computational amplifier, in making a differential to single-ended conversion or in rejecting a common mode signal. FIGURE 6. Three-op-amp Instrumentation Amplifier The first stage of this instrumentation amplifier is a differential-input, differential-output amplifier, with two voltage followers. These two voltage followers assure that the input impedance is over 100MΩ. The gain of this instrumentation amplifier is set by the ratio of R2/R1. R3 should equal R1 and R4 equal R2. Matching of R3 to R1 and R4 to R2 affects the CMRR. For good CMRR over temperature, low drift resistors should be used. Making R4 slightly smaller than R2 and adding a trim pot equal to twice the difference between R2 and R4 will allow the CMRR to be adjusted for optimum. 4.2.2 Two-op-amp Instrumentation Amplifier A two-op-amp instrumentation amplifier can also be used to make a high-input impedance DC differential amplifier (Figure 7). As in the two-op-amp circuit, this instrumentation amplifier requires precise resistor matching for good CMRR. R4 should equal to R1 and R3 should equal R2. 10092221 FIGURE 5. Difference Application 10092222 4.2 Instrumentation Circuits The input impendance of the previous difference amplifier is set by the resistor R1, R2, R3 and R4. To eliminate the problems of low input impendance, one way is to use a voltage follower ahead of each input as shown in the following two instrumentation amplifiers. FIGURE 7. Two-op-amp Instrumentation Amplifier 4.3 Single-Supply Inverting Amplifier There may be cases where the input signal going into the amplifier is negative. Because the amplifier is operating in single supply voltage, a voltage divider using R3 and R4 is implemented to bias the amplifier so the input signal is within the input common-common voltage range of the amplifier. www.national.com 10 LMV721/LMV722 Application Notes (Continued) The capacitor C1 is placed between the inverting input and resistor R1 to block the DC signal going into the AC signal source, VIN. The values of R1 and C1 affect the cutoff frequency, fc = 1⁄2π R1C1. As a result, the output signal is centered around mid-supply (if the voltage divider provides V+/2 at the non-inverting input). The output can swing to both rails, maximizing the signal-to-noise ratio in a low voltage system. 10092225 FIGURE 10. Frequency Response of Simple Low-pass Active Filter in Figure 9 Note that the single-op-amp active filters are used in to the applications that require low quality factor, Q(≤ 10), low frequency (≤ 5KHz), and low gain (≤ 10), or a small value for the product of gain times Q(≤ 100). The op amp should have an open loop voltage gain at the highest frequency of interest at least 50 times larger than the gain of the filter at this frequency. In addition, the selected op amp should have a slew rate that meets the following requirement: Slew Rate ≥ 0.5 x (ωH VOPP) X 10 −6V/µsec Where ωH is the highest frequency of interest, and VOPP is the output peak-to-peak voltage. 10092223 FIGURE 8. Single-Supply Inverting Amplifier 4.4 Active Filter 4.4.1 Simple Low-Pass Active Filter The simple low-pass filter is shown in Figure 9. Its low-pass frequency gain (ω → o) is defined by −R3/R1. This allows low-frequency gains other than unity to be obtained. The filter has a −20dB/decade roll-off after its corner frequency fc. R2 should be chosen equal to the parallel combination of R1 and R3 to minimize error due to bias current. The frequency response of the filter is shown in Figure 10. 10092244 FIGURE 11. A Battery Powered Microphone Preamplifier Here is a LMV721 used as a microphone preamplifier. Since the LMV721 is a low noise and low power op amp, it makes it an ideal candidate as a battery powered microphone preamplifier. The LMV721 is connected in an inverting configuration. Resistors, R1 = R2 = 4.7kΩ, sets the reference half way between VCC = 3V and ground. Thus, this configures the op amp for single supply use. The gain of the preamplifier, which is 50 (34dB), is set by resistors R3 = 10kΩ and R4 = 500kΩ. The gain bandwidth product for the LMV721 is 10 MHz. This is sufficient for most audio application since the audio range is typically from 20 Hz to 20kHz. A resistor R5 = 5kΩ is used to bias the electret microphone. Capacitors C1 = C2 = 4.7µF placed at the input and output of the op amp to block out the DC voltage offset. 10092224 FIGURE 9. Simple Low-Pass Active Filter 11 www.national.com LMV721/LMV722 Connection Diagrams 5-Pin SC-70/SOT23-5 8-Pin SO/MSOP/LLP* 10092299 Top View Note: LLP-8 exposed DAP can be electrically connected to ground for improved thermal performance. 10092263 Top View Ordering Information Temperature Range Package Industrial −40˚C to +85˚C 8-Pin Small Outline 8-pin MSOP 8-pin LLP 5-Pin SOT23 5-Pin SC-70 LMV722M LMV722MX LMV722MM LMV722MMX LMV722LD LMV722LDX LMV721M5 LMV721M5X LMV721M7 LMV721M7X LMV722M LMV722 L22 A30A A20 Rails 2.5k Units Tape and Reel 1k Units Tape and Reel 3.5k Units Tape and Reel 1k Units Tape and Reel 3.5k Units Tape and Reel 1k Units Tape and Reel 3k Units Tape and Reel 1k Units Tape and Reel 3k Units Tape and Reel M08A MUA08A LDA08C MF05A MAA05A Package Marking Transport Media NSC Drawing www.national.com 12 LMV721/LMV722 Physical Dimensions unless otherwise noted inches (millimeters) 8-Pin SOIC NS Package Number M08A 8-Pin LLP NS Package Number LDA08C 13 www.national.com LMV721/LMV722 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Pin MSOP NS Package Number MUA08A 5-Pin SOT23 NS Package Number MF05A www.national.com 14 LMV721/LMV722 10MHz, Low Noise, Low Voltage, and Low Power Operational Amplifier Physical Dimensions inches (millimeters) unless otherwise noted (Continued) SC70-5 NS Package Number MAA05A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. 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