SQ20953AIC

Application Note: SQ20953 High Efficiency Fast Response, 3A, 30V Input Synchronous Step Down Regulator Features The SQ20953 develops a high efficiency synchronous step-down DC/DC converter ， which is capable of delivering 3A load current. The SQ20953 operates over a wide input voltage range from 4.5V to 30V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. • Low RDS(ON) for Internal Switches (Top/Bottom): 110/70 mΩ • 4.5-30V Input Voltage Range • Internal Compensation • Internal 1ms Soft-start Limits the Inrush Current • Adjustable Switching Frequency Range: 500kHz to 2.5MHz • 3A Output Current Capability • 1.5% 0.6V Reference • Low Quiescent Current • Cycle-by-cycle Peak Current Limit • Short Circuit Protection • Thermal Shutdown and Auto Recovery • RoHS Compliant and Halogen Free • Compact Package: TSOT23-8 OO KO O General Description Ordering Information on fi BS IN yC CBS VIN dF Efficiency vs. Load Current (L=6.8µH/CDRH8D43-6R8) 100 VOUT L erg R1 FB Sil EN LCD-TV SetTop Box Notebook Storage High Power AP Router Networking LX CIN ON/ OFF • • • • • • R2 FS C1(opt.) COUT 80 Efficiency (%) orp Typical Applications Note -- de nti a Package type TSOT23-8 lP Applications .C Ordering Number SQ20953AIC rep are The SQ20953 is available in TSOT23-8 package. or W The SQ20953 adopts peak current control scheme. The switching frequency is adjustable from 500kHz to 2.5MHz using an external resistor. The device also features ultra low quiescent operating to achieve high efficiency under light load. The internal soft-start limits inrush current during power on. 60 40 VIN=9V, VOUT=5V VIN=12V, VOUT=5V VIN=24V, VOUT=5V GND RFS 20 0 1 10 100 1000 10000 Load Current (mA) Figure 1. Schematic Diagram AN_SQ20953 Rev. 0.9 © 2020 Silergy Corp. Figure 2. Efficiency vs. Load Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 All Rights Reserved. SQ20953 FB 1 8 EN FS 2 7 BS GND 3 6 LX GND 4 5 IN Top Mark: Sil erg yC orp .C on fi de nti a lP GND IN LX BS EN or W FS dF FB C5xyz (Device code: C5, x=year code, y=week code, z= lot number code) Pin Description Pin Number Output feedback pin. Connect this pin to the center point of the output resistor 1 divider (as shown in Figure 1) to program the output voltage: V OUT=0.6×(1+R1/R2) Frequency programming pin. Connect a resistor to ground to program a switching 2 frequency between 500kHz to 2.5MHz. The switching frequency equals to: fSW=106800/ (RFS+7) kHz, where RFS is in kΩ. 3,4 Ground pin. 5 Input pin. Decouple this pin to the GND pin with at least a 4.7µF ceramic capacitor. 6 Inductor pin. Connect this pin to the switching node of inductor. 7 Boot-strap pin. Supply high side gate driver. Connect a 0.1µF to the LX pin. 8 Enable control. Pull high to turn on. Do not leave it floating. rep are Pin Name OO KO O Pinout (top view) AN_SQ20953 Rev. 0.9 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 2 All Rights Reserved. SQ20953 Block Diagram IN HS Current Sense Internal Power Input UVLO HS Current Limitation VCC OO KO O Comp BS HSFET VCC EN LX Enable Threshold PWM Control & Protect Logic HS Current Sense Internal SST Comp LSFET GND Comp Error Amp Rc rep are VREF FB VCC dF Slope Compensation LS Current Sense or W Internal clock FS SCP LS current Limitation OTP lP Cc de nti a Absolute Maximum Ratings (Note 1) yC orp .C on fi IN to GND --------------------------------------------------------------------------------- -------------- -0.3V to 33V LX, FB, EN, FS to GND------------------------------------------------------------------------------------------ -0.3V to 33V BS-LX ------------------------------------------------------------------------------------------------------------------- -0.3V to 4V Dynamic LX voltage in 20ns duration --------------------------------------------------------------------- IN+3V to GND-6V Power Dissipation, PD @ TA = 25°C TSOT23-8 ---------------------------------------------------------------------------- 2W Package Thermal Resistance (Note 2) θ JA --------------------------------------------------------------------------------------------------------------- 60.2°C/W θ JC --------------------------------------------------------------------------------------------------------------- 11.2°C/W Junction Temperature Range ------------------------------------------------------------------------------------- -40°C to 150°C Ambient Temperature Range ------------------------------------------------------------------------------------- -40°C to 105°C Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°C Storage Temperature Range -------------------------------------------------------------------------------------- -65°C to 150°C erg Recommended Operating Conditions (Note 3) Sil Supply Input Voltage ------------------------------------------------------------------------------------------- ------- 4.5V to 30V Junction Temperature Range ------------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------- -40°C to 85°C AN_SQ20953 Rev. 0.9 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 3 All Rights Reserved. SQ20953 Electrical Characteristics (VIN = 12V, TJ= -40°C to +125°C. Typical values are at TJ=25°C, unless otherwise specified. The values are guaranteed by test, design or statistical correlation.) Test Conditions Min 4.5 IOUT=0, VFB=VREF×105% EN=0 TJ=25°C TJ= -40~125°C VFB=VCC VREF 0.591 0.581 -50 or W IFB RDS(ON)1 RDS(ON)2 ILIM,TOP VENL VENH VUVLO VHYS Typ 10 1.6 0.6 0.6 110 70 RFS=206.6k 1.5 3.8 V nA mΩ mΩ A V V V V 2.5 MHz 500 630 kHz 0.4 1 80 120 2.4 ms ns ns de nti a TSD,HYS 4.5 Unit V µA µA 400 RFS=206.6k TSD 4.15 0.4 0.5 lP tSS rep are RFS=35.7k~206.6k dF 3.8 fOSC Max 30 27 4 0.609 0.619 50 190 110 6.8 0.5 OO KO O Symbol VIN IQ ISHDN 150 °C 15 °C on fi Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current Top FET RON Bottom FET RON Top FET Current Limit EN Input Voltage Low EN Input Voltage High Input UVLO Threshold UVLO Hysteresis Oscillator Frequency Program Range Oscillator Frequency Accuracy Soft-start Time Min ON Time Min OFF Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis θ JA is measured in the natural convection at TA = 25°C on a two-layer Silergy evaluation board. yC Note 2: orp .C Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Sil erg Note 3: The device is not guaranteed to function outside its operating conditions. AN_SQ20953 Rev. 0.9 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 4 All Rights Reserved. SQ20953 Typical Performance Characteristics (FSW=500kHz, TA = 25°C) Efficiency vs. Load Current Load Transient (L=6.8µH/CDRH8D43-6R8) (VIN=12V, VOUT=5V, IOUT=0.3A ~ 3A) 100 IL 40 VIN=9V, VOUT=5V VIN=12V, VOUT=5V VIN=24V, VOUT=5V 0 1 10 100 1000 10000 Time (40μs/div) dF Load Current (mA) rep are Startup from VIN VLX 10V/div IL 2V/div 2A/div on fi VOUT de nti a 10V/div Shutdown from VIN (VIN=12V, VOUT=5V, IOUT=3A) VIN 10V/div VLX 10V/div VOUT 2V/div IL 2A/div lP (VIN=12V, VOUT=5V, IOUT=3A) VIN 2A/div or W Efficiency (%) 60 20 0.5V/div OO KO O ΔVOUT 80 Time (20ms/div) orp .C Time (4ms/div) Shutdown from Enable (VIN=12V, VOUT=5V, IOUT=3A) EN 5V/div VLX 10V/div IL 5V/div VLX 10V/div 2V/div VOUT 2V/div 2A/div IL 2A/div erg EN Sil VOUT yC Startup from Enable (VIN=12V, VOUT=5V, IOUT=3A) Time (4ms/div) AN_SQ20953 Rev. 0.9 © 2020 Silergy Corp. Time (100μs/div) Silergy Corp. Confidential- Prepared for Customer Use Only 5 All Rights Reserved. SQ20953 Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=5V, 0A to Short) (VIN=12V, VOUT=5V, 3A to Short) VOUT 5V/div IL IL Time (10ms/div) dF Time (10ms/div) rep are Output Ripple (VIN=12V, VOUT=5V, IOUT= 3A) VLX 10V/div IL de nti a lP 10mV/div 2A/div or W 2A/div ΔVOUT 5V/div OO KO O VOUT Sil erg yC orp .C Time (2μs/div) on fi 2A/div AN_SQ20953 Rev. 0.9 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 6 All Rights Reserved. SQ20953 Output Capacitor COUT The output capacitor is selected to handle the output ripple noise requirements. Both steady state ripple and transient requirements must be taken into consideration when selecting this capacitor. For the best performance, it is recommended to use X5R or better grade ceramic capacitor greater than 22µF capacitance. Operation OO KO O The SQ20953 develops a high efficiency synchronous step-down DC/DC converter, which is capable of delivering 3A load current. The SQ20953 operates over a wide input voltage range from 4.5V to 30V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SQ20953 adopts peak current control scheme. The switching frequency is adjustable from 500kHz to 2.5MHz using an external resistor. The device also features ultra low quiescent operating to achieve high efficiency under light load. The internal soft-start limits inrush current during power on. L= fSW  IOUT,MAX  40% rep are where fsw is the switching frequency and IOUT,MAX is the maximum load current. The SQ20953 is quite tolerant of different ripple current amplitude. Consequently, the final choice of inductance can be slightly off the calculation value without significantly impacting the performance. 2) The saturation current rating of the inductor must be selected to be greater than the peak inductor current under full load conditions. lP Because of the high integration in the IC, the application circuit based on this regulator IC is rather simple. Only input capacitor CIN, output capacitor COUT, output inductor L and feedback resistors (R1 and R2) need to be selected for the targeted applications specifications. VOUT (1 − VOUT /VIN,MAX ) dF Applications Information or W Output Inductor L There are several considerations in choosing this inductor. 1) Choose the inductance to provide the desired ripple current. It is suggested to choose the ripple current to be about 40% of the maximum output current. The inductance is calculated as: 0.6V R1 . VOUT -0.6V orp 0.6VFB yC R2 = .C on fi de nti a Feedback Resistor Dividers R1 and R2 Choose R1 and R2 to program the proper output voltage. To minimize the power consumption under light loads, it is desirable to choose large resistance values for both R1 and R2. A value of between 10kΩ and 1MΩ is highly recommended for both resistors. If VOUT is 3.3V, R1=100k is chosen, then using following equation, R2 can be calculated to be 22.1k: GND VOUT R1 R2 Sil erg Input Capacitor CIN The ripple current through input capacitor is calculated as： ICIN_RMS =IOUT  D(1-D) . AN_SQ20953 Rev. 0.9 3) VOUT(1-VOUT/VIN,MAX) 2  fSW  L The DCR of the inductor and the core loss at the switching frequency must be low enough to achieve the desired efficiency requirement. It is desirable to choose an inductor with DCR