SQ27403FCA

Application Note: SQ27403 High Efficiency Fast Response, 3.5A, 40V Input Synchronous Step Down Regulator Advanced Design Specification General Description Features The SQ27403 develops a high efficiency synchronous step-down DC/DC converter capable of delivering 3.5A load current. The SQ27403 operates over a wide input voltage range from 4.2V to 40V 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): 115/80mΩ  4.2-40V Input Voltage Range  Internal Compensation  Internal 1ms Soft-start Limits the Inrush Current  Adjustable Switching Frequency Range: 300kHz to 2.2MHz  3.5A Output Current Capability  ±1% 0.6V Reference  Cycle-by-cycle Peak Current Limitation  Short Circuit Protection  Thermal Shutdown and Auto Recovery  RoHS Compliant and Halogen Free  Compact Package: SO8E The SQ27403 adopts peak current control scheme. The switching frequency is adjustable from 300kHz to 2.2MHz using an external resistor. The device also features ultra low quiescent operating to achieve high efficiency under light load. And the internal soft-start limits inrush current during power on. Ordering Information Applications SQ27403 □(□□)□ Temperature Code Package Code Optional Spec Code Ordering Number SQ27403FCA Package Type SO8E  Automotive  Industrial  High-Voltage DC/DC Converters Note Typical Application Efficiency vs. Output Current 100 VIN 95 PG IN 90 CBS ON/OFF VOUT L LX EN R1 FS C OUT Efficiency (%) BS C IN 85 80 75 70 65 FB R FS VIN =9V, VOUT =5V VIN =12V, VOUT =5V VIN =24V, VOUT =5V VIN =40V, VOUT =5V 60 GND R2 55 50 0.001 0.01 0.10 1 Output Current (A) Figure1. Schematic Diagram AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. Figure2. Efficiency vs. Output Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 All Rights Reserved. SQ27403 Pinout (Top View) Pin Name BS 1 8 PG LX 2 7 GND IN 3 6 FS EN 4 5 FB (SO8E) Top Mark: CYWxyz (device code: CYW, x=year code, y=week code, z= lot number code) Pin Number Pin Description BS 1 LX 2 Boot-strap pin. Supply high side gate driver. Connect a 0.1µF ceramic capacitor between the BS and the LX pin. Inductor pin. Connect this pin to the switching node of inductor. IN 3 Input pin. Decouple this pin to GND pin with at least a 4.7μF ceramic capacitor. EN 4 FB 5 FS 6 GND 7 PG 8 Enable control. Pull high to turn on. Do not leave it floating. Output feedback pin. Connect this pin to the center point of the output resistor divider (as shown in Figure 1) to program the output voltage: V OUT=0.6×(1+R1/R2) Frequency setting pin. Connect a resistor from this pin to GND to program the switching frequency. The switching frequency equals to: fsw(kHz) =106/(9.3×RFS(kΩ)+30) Ground. Power good indicator. Open drain output. Externally pulled high when V OUT is within regulation range. Otherwise, internally pulled low. Block Diagram IN HS Current Sense Comp Internal Power Input UVLO HS current Limitation VCC BS HSFET VCC EN LX Enable Threshold PWM Control & Protect Logic Internal clock FS LS Current Sense VCC LSFET Slope Compensation HS Current Sense GND Internal SST Comp FB PG Comp VREF LS current Limitation Error Amp Rc SCP OTP Cc Figure3. Block diagram AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 2 All Rights Reserved. SQ27403 Absolute Maximum Ratings (Note 1) IN to GND -------------------------------------------------------------------------------------------------- -0.3V to 44V LX, FB, EN, FS, PG to GND--------------------------------------------------------------------------------------- -0.3V to 44V BS-LX ---------------------------------------------------------------------------------------------------------- 4V Power Dissipation, P D @ T A = 25°C, SO8E --------------------------------------------------------------- 2.5W Package Thermal Resistance (Note 2) θ JA ------------------------------------------------------------------------------------------------------- -- 40°C/W θ JC ------------------------------------------------------------------------- ----------------------------------- 12°C/W Junction Temperature Range ----------------------------------------------------------------------------------- -40°C to 150°C Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°C Storage Temperature Range ------------------------------------------------------------------------------------- -65°C to 150°C Recommended Operating Conditions (Note 3) Supply Input Voltage ------------------------------------------------------------------------------------------------- 4.2V to 40V Ambient Temperature Range ----------------------------------------------------------------------------------- -40°C to 105°C AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 3 All Rights Reserved. SQ27403 Electrical Characteristics (VIN = 12V, TA = -40°C~105°C, unless otherwise specified, the values are guaranteed by test design or statistical correlation) Parameter Symbol Test Conditions Min Typ Max Unit Input Voltage Range VIN 4.2 40 V Input UVLO Threshold 3.55 4.0 4.2 V VUVLO UVLO Hysteresis VHYS 0.3 V IOUT=0, VFB=VREF×105%, 10 18 25 TA=25°C Quiescent Current IQ µA IOUT=0, VFB=VREF×105%, 5 18 33 TA= -40°C~105°C EN=0, TA=25°C 1 Shutdown Current ISHDN µA EN=0, TA= -40°C~105°C 5 TA= 25°C 0.594 0.6 0.606 Feedback Reference VREF V Voltage TA= -40°C~105°C 0.588 0.6 0.612 FB Input Current IFB VFB=3V -200 200 nA Top FET RON RDS(ON)1 115 mΩ Bottom FET RON RDS(ON)2 80 mΩ Top FET Current Limit ILIM,TOP 5.5 A EN High Threshold VENH 1.08 1.2 1.32 V EN Low Threshold VENL 0.9 1.0 1.1 V Hiccup Duty Cycle DHICCUP 12.5 % Output Discharge Current IDIS 45 mA Oscillator Frequency fOSC,RNG RFS=27.4k~200k(TBD) 300 2200 kHz Program Range Oscillator Frequency fOSC=2MHz, with RFS resistor fOSC,ACC -15% 15% fOSC Accuracy of 1% accuracy Output Under Voltage VUVP 33% VREF Protection Threshold VFB falling, PG from high to 89% VREF low VFB rising, PG from low to 93% VREF high Power Good Threshold VPG VFB rising, PG from high to 115% VREF low VFB falling, PG from low to 113% VREF high tPG_F PG falling edge 10 µs PG Delay tPG_R PG rising edge 150 µs Power Good Output Low VPG,LOW IPG_LOW=10mA 0.7 V Voltage Soft-start Time tSS 1 ms Min ON Time tON,MIN 90 ns Min OFF Time tOFF,MIN FOSC=2MHz 90 ns Thermal Shutdown TSD 160 °C Temperature Thermal Shutdown TSD,HYS 20 °C Hysteresis AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 4 All Rights Reserved. SQ27403 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. Note 2: θ JA is measured in the natural convection at T A = 25°C on a two-layer Silergy demo board. Note 3: The device is not guaranteed to function outside its operating conditions. Note 4: High junction temperatures degrade operating lifetime. Operating lifetime is derated for junction temperatures greater than 125°C. AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 5 All Rights Reserved. SQ27403 Typical Performance Characteristics Load Transient Efficiency vs. Output Current (VIN =12V, VOUT =5V, IOUT =0.35A ~ 3.5A) 100 95 Efficiency (%) 90 ΔVOUT 0.2V/div 85 80 75 IL 70 2A/div 65 VIN =9V, VOUT =5V VIN =12V, VOUT =5V VIN =24V, VOUT =5V VIN =40V, VOUT =5V 60 55 50 0.001 0.01 0.10 1 Output Current (A) Time (40μs/div) Startup from VIN Shutdown from VIN (VIN =12V, VOUT =5V, IOUT =3.5A) (VIN =12V, VOUT =5V, IOUT =3.5A) VIN 10V/div VIN 10V/div VLX 10V/div VLX 10V/div VOUT 2V/div VOUT IL 2V/div IL 2A/div Time (2ms/div) Time (2ms/div) Startup from Enable Shutdown from Enable (VIN =12V, VOUT =5V, IOUT =3.5A) (VIN =12V, VOUT =5V, IOUT =3.5A) EN 5V/div VLX 10V/div VOUT 2V/div IL 2A/div EN 5V/div VLX 10V/div VOUT 2V/div IL Time (2ms/div) AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. 2A/div 2A/div Time (100µs/div) Silergy Corp. Confidential- Prepared for Customer Use Only 6 All Rights Reserved. SQ27403 Short Circuit Protection Short Circuit Protection (VIN =12V, VOUT =5V, 0A to Short) (VIN =12V, VOUT =5V, 3.5A to Short) VOUT IL 2V/div VOUT IL 2A/div Time (20ms/div) 2V/div 2A/div Time (20ms/div) Output Ripple (VIN =12V, VOUT =5V, IOUT = 3.5A) ΔVOUT VLX IL 10mV/div 5V/div 2A/div Time (2μs/div) AN_SQ27403 Rev. 0.0 © 2020 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 7 All Rights Reserved. SQ27403 Operation The SQ27403 develops a high efficiency synchronous step-down DC/DC converter capable of delivering 3.5A load current. The SQ27403 operates over a wide input voltage range from 4.2V to 40V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SQ27403 adopts peak current control scheme. The switching frequency is adjustable from 300kHz to 2.2MHz using an external resistor. The device also features ultra low quiescent operating to achieve high efficiency under light load. And the internal soft-start limits inrush current during power on. 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 an X5R or better grade ceramic capacitor greater than 22μF capacitance. 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: Applications Information Because of the high integration in the SQ27403, the application circuit based on this regulator 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. 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: L= where fsw is the switching frequency and IOUT,MAX is the maximum load current. The SQ27403 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. ISAT, MIN  IOUT, MAX  VOUT 0.6V R2 =  R1 VOUT -0.6V 0.6VFB GND R1 3) R2 Input Capacitor CIN: The ripple current through input capacitor is calculated as： I  I  D(1  D) . CIN _ RMS VOUT(1-VOUT/VIN,MAX) fSW  IOUT,MAX  40% OUT To minimize the potential noise problem, place a typical X5R or better grade ceramic capacitor really close to the IN and GND pins. Care should be taken to minimize the loop area formed by CIN, and IN/GND pins. In this case, a 4.7μF low ESR ceramic capacitor is recommended. 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