SA24401FCA

Application Note: SA24401/SA24401B 1.8μA Quiescent Current, 0.6A, 40V Input Synchronous Step Down Regulator Advanced Design Specification General Description Features The SA24401/SA24401B develops a high efficiency synchronous step-down DC/DC converter capable of delivering 0.6A load current. The device operates over a wide input voltage range from 4.2V to 40V and integrates main switch and synchronous switch with low RDS(ON) to minimize the conduction loss. The SA24401/SA24401B adopts peak current control scheme. The device offers an adjustable version (SA24401) and a fixed-output voltage version of 3.3V (SA24401B). The SA24401/SA24401B operates under 500kHz / 2.1MHz fixed switching frequency. 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            Applications    Ordering Information SA24401 □(□□)□ Low RDS(ON) for Internal Switches (Top/Bottom): 225mΩ/150mΩ 4.2V to 40V Input Voltage Range 0.6A Output Current Capability Low Quiescent Current Switching Frequency -- SA24401: 500kHz -- SA24401B: 2.1MHz Internal Soft-start Limits the Inrush Current ±1% 1V Reference Short Circuit Protection Thermal Shutdown and Auto Recovery Power Good Indicator Compact Package: SO8E Automotive Industrial High-Voltage DC/DC Converters Temperature Code Package Code Optional Spec Code Ordering Number SA24401FCA SA24401BFCA Package Type SO8E SO8E Note Typical Application CBS VIN BS IN L VOUT LX CIN R1 ON/ OFF COUT FB EN R2 PG VCC CVCC GND Figure1. Schematic Diagram (SA24401) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 1 All Rights Reserved. AN_ SA24401/SA24401B CBS VIN BS IN L VOUT LX CIN COUT ON/ OFF OUT EN PG VCC CVCC GND Figure2. Schematic Diagram (SA24401B) Pinout (Top View) BS 1 LX 2 IN 3 EN 4 Exposed Pad 8 PG 7 GND 6 VCC 5 FB/OUT (SO8E) Top Mark: BZAxyz for SA24401FCA (device code: BZA, x=year code, y=week code, z= lot number code) CHMxyz for SA24401BFCA (device code: CHM, x=year code, y=week code, z= lot number code) Pin Pin Name Pin Description Number Boot-strap pin. Supply high side gate driver. Connect a 0.1µF ceramic capacitor BS 1 between BS and LX pin. LX 2 Inductor pin. Connect this pin to the switching node of the inductor. IN 3 EN 4 FB/OUT 5 VCC 6 GND 7 PG 8 Exposed Pad — AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. Power supply input. Connect a minimum of 4.7μF ceramic capacitor from IN to GND. Enable control. Pull high to enable the device, pull low to disable the device. Do not leave this pin floating. SA24401 (Adjustable Output): Feedback input. Connect FB to a resistive divider between the Buck output and GND to set the output voltage: VOUT=1V×(1+R1/R2) SA24401B (Fixed Output): Output voltage sense input. Internal 3.3V bias supply. Connect a 1μF ceramic capacitor from VCC to GND. Do not load this pin externally. Ground. Power good indicator. Open drain output. Externally pulled high when the output voltage is above 95% of regulation voltage. Pulled low otherwise. Exposed pad. Connect the exposed pad to a large copper ground plane for effective power dissipation. The exposed pad must be connected to GND. Silergy Corp. Confidential- Prepared for Customer Use Only 2 All Rights Reserved. AN_ SA24401/SA24401B Block Diagram IN 3.3V LDO EN BG OSC VCC CS BS CS & SLOPE COMP SS Logic Control PWM VREF FB LX gm VPG,TH PG GND Figure3. Block Diagram (SA24401) EN IN 3V 3.3V LDO BG OSC VCC CS BS CS & SLOPE COMP SS Logic Control PWM VREF LX gm OUT VPG,TH PG GND Figure4. Block Diagram (SA24401B) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 3 All Rights Reserved. AN_ SA24401/SA24401B Absolute Maximum Ratings (Note 1) IN to GND ------------------------------------------------------------------------------------- ------------- -0.3V to 44V LX, EN, PG to GND------------------------------------------------------------------------------------ -0.3V to 44V VCC, FB/OUT --------------------------------------------------------------------------------------------------------- -0.3V to 4V BS-LX ------------------------------------------------------------------------------------------------------------------- -0.3V to 4V Power Dissipation, PD @ TA = 25°C, SO8E-------------------------------------------------------------------------------- 2.5W Package Thermal Resistance (Note 2) θJA ----------------------------------------------------------------------------------------------------------------- 40°C/W θJC ----------------------------------------------------------------------------------------------------------------- 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) IN ------------------------------------------------------------------------------------------------------------------------ 4.2V to 40V Ambient Temperature Range ----------------------------------------------------------------------------------- -40°C to 125°C AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 4 All Rights Reserved. AN_ SA24401/SA24401B Electrical Characteristics (VIN = 12V, TA = -40°C~125°C, unless otherwise specified, the values are guaranteed by test design or statistical correlation) Parameter Input Voltage Range Input UVLO Threshold Input UVLO Hysteresis Symbol VIN VUVLO VHYS Quiescent Current IQ Shutdown Current ISHDN Feedback Reference Voltage VREF FB Input Current Output Voltage Set-point Top FET RON Bottom FET RON Top FET Current Limit PFM Peak Current Soft-start Time Switching Frequency Switching Frequency EN Input Voltage High EN Input Voltage Low IFB VSET RDS(ON)1 RDS(ON)2 ILMT,TOP IPK,PFM tSS fSW fSW VEN,H VEN,L Power Good Threshold Power Good Delay Time VPG tPG_F tPG_R VPG,L Test Conditions SA24401:TA=25°C SA24401:TA= -40~125°C SA24401B:TA=25°C SA24401B:TA= -40~125°C EN=0, TA = 25°C EN=0, TA= -40°C~125°C SA24401:TA=25°C,CCM SA24401: TA= -40°C~125°C, CCM VFB=3.3V SA24401B SA24401B, CCM SA24401, CCM Min 4.2 3.8 Typ 1 6 10 3 5 1 2 1.01 Unit V V V µA µA µA µA µA µA V 1 1.02 V 50 3.4 nA V mΩ mΩ A mA ms MHz MHz V V 4 3 4 0.2 5 5 1.8 1.8 0.99 0.98 -50 3.2 1.95 0.464 1.6 3.3 225 150 1.2 375 1 2.1 0.5 Max 40 4.2 2.25 0.536 0.5 VOUT rising, PG from low to high VOUT falling, PG from high to low Low to high High to low IPG=1mA 95 91.5 93.75 300 20 %VO,SET 96 %VO,SET µs µs V µA ns µs ns Power Good Output Low 0.04 PG High Leakage Current 1 Minimum ON Time tON,MIN 65 Maximum ON Time tON,MAX 2.1 Minimum OFF Time tOFF,MIN 70 Output Under Voltage Protection VUVP 65 %VREF Threshold Output UVP Delay tUVP,DLY 60 µs Thermal Shutdown Temperature TSD 160 °C Thermal Shutdown Hysteresis THYS 20 °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. Note 2: θ JA is measured in the natural convection at TA = 25°C on a two-layer Silergy demo board. Note 3: The device is not guaranteed to function outside its operating conditions. AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 5 All Rights Reserved. AN_ SA24401/SA24401B Typical Performance Characteristics (SA24401) Load Transient Response Efficiency vs. Output Current (VIN=12V, VOUT=1.8V,IOUT=0.06~0.6A) 100 VIN=5V,VOUT=1.8V VIN=12V,VOUT=1.8V VIN=18V,VOUT=1.8V 95 Efficiency (%) 90 VOUT 100mV/div 85 80 75 IOUT 500mA/div 70 65 60 0.001 0.01 0.1 Time (200μs/div) Output Current (A) Startup from VIN Shutdown from VIN (VIN=12V, VOUT=1.8V, IOUT=0A) (VIN=12V, VOUT=1.8V, IOUT=0A) VIN 10V/div VIN 10V/div VOUT 2V/div VOUT 2V/div 10V/div VLX VLX IL 500mA/div IL Time (2ms/div) VIN VOUT 500mA/div Time (100ms/div) Startup from VIN Shutdown from VIN (VIN=12V, VOUT=1.8V, IOUT=0.6A) (VIN=12V, VOUT=1.8V, IOUT=0.6A) 10V/div VIN 10V/div 2V/div VOUT 2V/div VLX VLX 10V/div 10V/div 10V/div IL 500mA/div IL Time (2ms/div) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. 500mA/div Time (10ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 6 All Rights Reserved. AN_ SA24401/SA24401B Startup from Enable Shutdown from Enable (VIN=12V, VOUT=1.8V, IOUT=0A) (VIN=12V, VOUT=1.8V, IOUT=0A) EN 5V/div EN 5V/div VOUT 2V/div VOUT 2V/div VLX 10V/div VLX 10V/div IL 500mA/div IL Time (800μs/div) Startup from Enable Shutdown from Enable (VIN=12V, VOUT=1.8V, IOUT=0.6A) 5V/div VOUT 2V/div IL Time (200ms/div) (VIN=12V, VOUT=1.8V, IOUT=0.6A) EN VLX 500mA/div EN 5V/div VOUT 2V/div VLX 10V/div 10V/div 500mA/div IL Time (800μs/div) 500mA/div Time (800μs/div) Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=1.8V,IOUT=0A→short) (VIN=12V, VOUT=1.8V,IOUT=0.6A→short) VOUT IL 2V/div 500mA/div Time (4ms/div) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. VOUT IL 2V/div 500mA/div Time (4ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 7 All Rights Reserved. AN_ SA24401/SA24401B Output Voltage Ripple Output Voltage Ripple (VIN=12V, VOUT=1.8V, IOUT=0A) (VIN=12V, VOUT=1.8V, IOUT=0.6A) ΔVOUT LX IL 20mV/div 5V/div 500mA/div Time (4μs/div) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. ΔVOUT LX IL 20mV/div 5V/div 500mA/div Time (2μs/div) Silergy Corp. Confidential- Prepared for Customer Use Only 8 All Rights Reserved. AN_ SA24401/SA24401B Typical Performance Characteristics (SA24401B) Load Transient Response Efficiency vs. Output Current (VIN=12V, VOUT=3.3V,IOUT=0.06~0.6A) 100 VIN=5V,VOUT=3.3V VIN=12V,VOUT=3.3V VIN=18V,VOUT=3.3V 98 Efficiency (%) 96 VOUT 50mV/div 94 92 90 88 IOUT 500mA/div 86 84 82 80 0.001 0.01 0.1 Time (200μs/div) Output Current (A) Startup from VIN Shutdown from VIN (VIN=12V, VOUT=3.3V, IOUT=0A) (VIN=12V, VOUT=3.3V, IOUT=0A) VIN 10V/div VIN 10V/div VOUT 2V/div VOUT 2V/div VLX VLX IL 500mA/div IL Time (2ms/div) Time (100ms/div) Startup from VIN Shutdown from VIN (VIN=12V, VOUT=3.3V, IOUT=0.6A) 10V/div VOUT 2V/div IL 500mA/div (VIN=12V, VOUT=3.3V, IOUT=0.6A) VIN VLX 10V/div 10V/div VIN 10V/div VOUT 2V/div VLX 10V/div 10V/div 500mA/div Time (2ms/div) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. IL 500mA/div Time (2ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 9 All Rights Reserved. AN_ SA24401/SA24401B Startup from Enable Shutdown from Enable (VIN=12V, VOUT=3.3V, IOUT=0A) (VIN=12V, VOUT=3.3V, IOUT=0A) EN 5V/div VOUT 2V/div VLX 10V/div IL 500mA/div EN 5V/div VOUT 2V/div VLX 10V/div IL Time (2ms/div) Startup from Enable Shutdown from Enable (VIN=12V, VOUT=3.3V, IOUT=0.6A) 5V/div VOUT 2V/div IL Time (800μs/div) (VIN=12V, VOUT=3.3V, IOUT=0.6A) EN VLX 500mA/div EN 5V/div VOUT 2V/div VLX 10V/div 10V/div 500mA/div IL Time (2ms/div) 500mA/div Time (800μs/div) Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=3.3V,IOUT=0A→short) (VIN=12V, VOUT=3.3V,IOUT=0.6A→short) VOUT IL 2V/div 500mA/div Time (10ms/div) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. VOUT 2V/div IL 500mA/div Time (10ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 10 All Rights Reserved. AN_ SA24401/SA24401B Output Voltage Ripple Output Voltage Ripple (VIN=12V, VOUT=3.3V, IOUT=0A) (VIN=12V, VOUT=3.3V, IOUT=0.6A) ΔVOUT ΔVOUT 10mV/div VLX 5V/div VLX 200mA/div IL IL Time (4μs/div) AN_SA24401/B Rev. 0.0 © 2019 Silergy Corp. 10mV/div 5V/div 500mA/div Time (400ns/div) Silergy Corp. Confidential- Prepared for Customer Use Only 11 All Rights Reserved. AN_ SA24401/SA24401B Applications Information Because of the high integration in the SA24401 /SA24401B, the application circuit based on this regulator is rather simple. Only input capacitor CIN, output capacitor COUT, output inductor L, VCC capacitor CVCC ,feedback resistors R1/R2 (only SA24401) need to be selected for the targeted applications specifications. L VOUT (1  VOUT/VIN,MAX ) FSW  IOUT,MAX  40% where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SA24401/SA24401B regulator 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. Feedback Resistor Dividers R1 and R2 2) The saturation current rating of the inductor must Choose R1 and R2 to program the proper output voltage. be selected to be greater than the peak inductor To minimize the power consumption under light loads, current under full load conditions. it is desirable to choose large resistance values for both R1 and R2. A value of between 10kΩ and 1MΩ is VOUT(1-VOUT/VIN,MAX) highly recommended for both resistors. If Vout is 1.8V, ISAT, MIN  IOUT, MAX  R1=100k is chosen, then using following equation, R2 2  FSW  L can be calculated to be 125k: VOUT 3) The DCR of the inductor and the core loss at the R1 1V switching frequency must be low enough to R2= R1 achieve the desired efficiency requirement. It is VOUT-1V 1VFB desirable to choose an inductor with DCR