SY8368QNC

Application Notes: AN_SY8368 High Efficiency Fast Response 8A Continuous, 16A Peak, 28V Input Synchronous Step Down Regulator General Description Features The SY8368 develops a high efficiency synchronous step-down DC-DC regulator capable of delivering 8A continuous, 16A peak current. The SY8368 operates over a wide input voltage range from 4V to 28V 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): 20/10 mΩ • Wide input voltage range: 4-28V • Instant PWM architecture to achieve fast transient responses • Internal 400uS softstart limits the inrush current • Pseudo-constant frequency: 800kHz. • 8A continuous/16A peak output current capability • ±1.5% 0.6V reference • Programmable peak current limit • Power good indicator • Output discharge function • Short circuit latch off protection • Over voltage latch off protection • Input UVLO • Over temperature protection • RoHS Compliant and Halogen Free • Compact package: QFN3x3-10 ar ed fo r The SY8368 adopts the instant PWM architecture to achieve fast transient responses for high step down applications and high efficiency at light loads. In addition, it operates at pseudo-constant frequency of 800kHz under continuous conduction mode to minimize the size of inductor and capacitor. SY8368 □ (□□)□ Tempera ture Code Packa ge Code Optional Spec Code Note -- Applications en Package type QFN3x3-10 • • • • .C on fid Ordering Number SY8368QNC tia l-P re p Ordering Information LCD-TV/Net-TV/3DTV Set Top Box Notebook High Power AP VIN Co rp Typical Applications IN PG PG (Open Drain Output) BS er gy CIN 10uF CBS 100nF High/Floating/Low ILMT Sil GND EN ON/OFF CVCC 2.2uF VCC VOUT=5V LX L 1.5uH C1 220pF R1 100k COUT 22uF×3 R3 1k FB R2 13.7k Figure 1 Schematic AN_SY8368 Rev. 0.9B Figure 2. Efficiency Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY8368 r Pinout (top view) fo (QFN3x3-10) Pin Number 1 PG 2 ILMT 3 FB 4 VC 5 BS 6 IN GND LX 7,8 9 10 Pin Description Enable control. Pull this pin high to turn on the IC. Do not leave this pin floating. Power good Indicator. Open drain output when the output voltage is within 90% to 120% of regulation point. tia l-P re p Pin Name EN ar ed Top Mark: YWxyz, (Device code: YW, x=year code, y=week code, z= lot number code) Sil er gy Co rp .C on fid en Current limit setting pin. The current limit is set to 8A, 12A or 16A when this pin is pull low, floating or pull high respectively. 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: Vout=0.6*(1+R1/R2) Internal 3.3V LDO output. Power supply for internal analog circuits and driving circuit. Bypass a capacitor to GND. Boot-Strap Pin. Supply high side gate driver. Decouple this pin to LX pin with 0.1uF ceramic cap. Input pin. Decouple this pin to GND pin with at least 10uF ceramic cap Ground pin Inductor pin. Connect this pin to the switching node of inductor AN_SY8368 Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY8368 Absolute Maximum Ratings (Note 1) IN, LX, PG, EN ------------------------------------------------------------------------------------------------------ -0.3V to 30V BS-LX, FB, ILMT, VCC ------------------------------------------------------------------------------------------- -0.3V to 4V Power Dissipation, PD @ TA = 25°C QFN3x3-10 -----------------------------------------------------------------------3.3W Package Thermal Resistance (Note 2) θ JA -----------------------------------------------------------------------------------------------------------------30°C/W θ JC ---------------------------------------------------------------------------------------------------------------- 4°C/W Junction Temperature Range ------------------------------------------------------------------------------------------------ 125°C Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°C Storage Temperature Range -------------------------------------------------------------------------------------- -65°C to 150°C Dynamic LX voltage in 50ns duration --------------------------------------------------------------------- IN+3V to GND-4V Recommended Operating Conditions (Note 3) fo r Supply Input Voltage ---------------------------------------------------------------------------------------------------- 4V to 28V Junction Temperature Range ------------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------- -40°C to 85°C Sil er gy Co rp .C on fid en tia l-P re p ar ed Block Diagram AN_SY8368 Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY8368 Electrical Characteristics (VIN = 12V, VOUT =5V, COUT = 100uF, TA = 25°C, IOUT = 2A unless otherwise specified) Parameter Input Voltage Range Quiescent Current Symbol VIN IQ Shutdown Current Feedback Reference Voltage FB Input Current Top FET RON Bottom FET RON Discharge FET RON Bottom FET Current Limit ISHDN VREF Test Conditions Min 4.0 IOUT=0, VFB=VREF*105% EN=0 0.591 VFB=4V Max 28 100 Unit V µA 3 0.6 10 0.609 µA V 50 nA mΩ mΩ Ω -50 20 10 50 ILMT=’0’ ILMT=Floating ILMT=’1’ 8 12 16 Vcc-0.8 A r IFB Rds(on)1 Rds(on)2 Rdis ILIM Typ Sil er gy Co rp .C on fid en tia l-P re p ar ed fo ILMT Rising Threshold VILMTH VCC V ILMT Falling Threshold VILMTL 0.8 V ILMT Floating Threshold VILMIF 1.3 2 V Soft Start Time TSS 400 µS EN Rising Threshold VENH 0.8 V EN Falling Threshold VENL 0.4 V Input UVLO Threshold 3.9 V VUVLO UVLO hysteresis VHYS 0.3 V Oscillator Frequency FOSC Vo=5V 0.68 0.8 0.92 MHz Min ON Time TON,MIN VIN=VINMAX 50 ns Min OFF Time TOFF,MIN 80 ns VCC Output VCC VIN=4V 3.2 3.3 3.4 V Output Over Voltage VFB Rising 115 120 125 %VREF Threshold Output Over Voltage 2 %VREF Hysteresis Output Over Voltage 20 us Delay Time Power Good Threshold VFB Rising (Good) 88 90 92 %VREF Power Good Hysteresis 2 %VREF Power Good Delay Time 10 us Thermal Shutdown TSD 150 °C Temperature Thermal Shutdown THYS 15 °C hysteresis 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 four-layer Silergy Evaluation Board.. Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8368 Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY8368 Typical Performance Characteristics Efficiency vs. Load Current Efficiency vs. Load Current 100 100 90 90 80 80 70 70 60 60 50 50 VIN=7.4V,VOUT=5.0V VIN=12V,VOUT=5.0V VIN=19V,VOUT=5.0V VIN=28V,VOUT=5.0V 40 30 VIN=5.0V,VOUT=3.3V VIN=12V,VOUT=3.3V VIN=19V,VOUT=3.3V VIN=28V,VOUT=3.3V 40 30 20 20 0.001 0.01 0.10 1.00 10.00 0.001 0.01 0.10 10.00 Load Current (A) fo r Load Current (A) 1.00 Efficiency vs. Load Current ar ed Efficiency vs. Load Current 95 95 85 85 75 65 tia l-P re p 75 65 55 55 45 VIN=5.0V,VOUT=1.8V VIN=12V,VOUT=1.8V VIN=19V,VOUT=1.8V VIN=28V,VOUT=1.8V 15 0.01 0.10 1.00 .C on 0.001 fid 25 Load Current (A) VIN=5.0V,VOUT=1.2V VIN=12V,VOUT=1.2V VIN=19V,VOUT=1.2V VIN=28V,VOUT=1.2V 35 en 35 45 25 15 10.00 0.001 0.01 0.10 1.00 Load Current (A) Load Transient (VIN=12V, VOUT=5V, ILOAD=2-6A) Co rp Load Transient (VIN=12V, VOUT=5V, ILOAD=0.8-8A) er gy ∆VOUT 100mV/div ∆VOUT IL 100mV/div 2A/div 5A/div Sil IL 10.00 Time (200µs/div) AN_SY8368 Rev. 0.9B Time (200µs/div) Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY8368 Startup from Enable Shutdown from Enable (VIN=12V, VOUT=5V, ILOAD=8A) (VIN=12V, VOUT=5V, ILOAD=8A) EN 5V/div VLX 10V/div VOUT IL EN 5V/div VLX 10V/div 5V/div VOUT 5V/div IL 5A/div 5A/div Time (400µs/div) Time (400µs/div) Shutdown from VIN (VIN=12V, VOUT=5V, ILOAD=8A) VOUT 5V/div IL 5A/div fo 10V/div ar ed VLX tia l-P re p 10V/div en VIN r Startup from VIN (VIN=12V, VOUT=5V, ILOAD=8A) 10V/div VLX 10V/div VOUT 5V/div IL 5A/div Time (2ms/div) fid Time (4ms/div) VIN .C on Short Circuit Protection er gy Co rp (VIN=12V, VOUT=5V, ILMT floating, Null Load to Short) VOUT 5A/div Sil IL 2V/div Time (100µs/div) AN_SY8368 Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 6 AN_SY8368 Output Ripple (VIN=12V, VOUT=5V, ILOAD=8A) 20mV/div VLX 5V/div IL 5A/div Frequency(kHz) ∆Vout(AC) Sil er gy Co rp .C on fid en tia l-P re p ar ed fo r Time (2µs/div) AN_SY8368 Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 7 AN_SY8368 Operation The SY8368 develops a high efficiency synchronous step-down DC-DC regulator capable of delivering 8A continuous, 16A peak current. The SY8368 operates over a wide input voltage range from 4V to 28V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SY8368 adopts the instant PWM architecture to achieve fast transient responses for high step down applications and high efficiency at light loads. In addition, it operates at pseudo-constant frequency of 800kHz under continuous conduction mode to minimize the size of inductor and capacitor. 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: VOUT (1 − VOUT /VIN, MAX ) FSW × I OUT, MAX × 40% ar ed L= where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SY8368 regulator IC 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. tia l-P re p Because of the high integration in the SY8368 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. fo r Applications Information 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 most applications, an X5R or better grade ceramic capacitor greater than 66uF capacitance can work well. The capacitance derating with DC voltage must be considered. Co rp 0.6V R2 = R1 . VOUT − 0.6V .C on fid en 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: 0.6VFB GND R1 R2 er gy Sil 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 10uF low ESR ceramic capacitor is recommended. AN_SY8368 Rev. 0.9B VOUT(1-VOUT/VIN,MAX) 2 ⋅ FSW ⋅ L VOUT Input capacitor CIN: The ripple current through input capacitor is calculated as： I = I ⋅ D(1 − D) . CIN _ RMS ISAT, MIN > IOUT, MAX + 3) 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