SY8286ARAC

Application Note: SY8286A High Efficiency Fast Response 6A, 23V Input Synchronous Step Down Regulator General Description Features The SY8286A develops a high efficiency synchronous step-down DC-DC regulator capable of delivering 6A current. The device integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SY8286A operates over a wide input voltage range from 4V to 23V. The DC-DC regulator adopts the instant PWM architecture to achieve fast transient responses for high step down applications and high efficiency at light load. The device provides various protection features for reliable operation. In addition, it operates at pseudoconstant frequency of 600kHz to minimize the size of inductor and capacitor. • Ordering Information SY8286 □(□□)□ Temperature Code Package Code Optional Spec Code Ordering Number SY8286ARAC Package type QFN3x3-20 Note -- • • • • • • • • • • • • • • • • • Low RDS(ON) for internal switches (top/bottom): 38/19 mΩ Wide input voltage range: 4-23V Instant PWM architecture to achieve fast transient responses Internal 1.3ms soft-start limits the inrush current Pseudo-constant frequency: 600kHz. 6A output current capability +/-1% internal reference voltage PFM/PWM selectable light l ad peration mode Optional bypass input Power good indicator Output discharge function Output current limit protection Hiccup mode output short circuit protection Output over voltage protection Input UVLO Ov r t mperature protection with auto recovery RoHS Compliant and Halogen Free Compact package: QFN3x3-20 Applications • • • • LCD-TV/Net-TV/3DTV Set Top Box Notebook High Power AP Typical Applications Figure 1 Schematic AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 1 SY8286A Pinout (top view) Top (QFN3x3-20) Mark: AWRxyz, (Device code: AWR, x=year code, y=week code, z= lot number code) Pin Name Pin Number BS 1 IN LX GND 2,3,4,5 6,19,20 7,8,18,EP PG 9 NC EN 10, 16 11 MODE 12 ILMT FB 13 14 BYP 15 VCC 17 Pin Description Boot-strap pin. Supply high side gate driver. Decouple this pin to LX pin with 0.1uF ceramic capacitor. Input pin. Decouple this pin to GND pin with at least 10uF ceramic cap Inductor pin. Connect this pin to the switching node of inductor Ground pin Power good Indicator. Open drain output when the output voltage is within 90% to 120% of regulation point. Not connected Enable pin. Pull this pin high to turn on IC. Do not leave this pin floating. Operating mode selection under light load. Pull this pin low for PFM operating, and pull this pin high for PWM operation. Do not leave this pin floating Output current limit threshold selection. Output feedback pin. Connect to the center point of resistor divider. External 3.3V bypass power supply input. Decouple this pin to GND with a 1uF ceramic capac tor. Leave this pin floating if it is not used. Internal 3.3V LDO output. Power supply for internal analog circuits and driving circuit. Decouple this pin to GND with a 2.2uF ceramic capacitor. AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 2 SY8286A Block Diagram IN Input UVLO Current Sense PG BS EN ILMT MODE Internal SST LX PWM Control & Protection Logic Current Sense OTP GND 0.6V FB IN BYP 3.1V 3.3V LDO VCC Absolute Maximum Ratings (Note 1) IN --------------------------------------------------------------------------------------------------------------------------------25V BS-LX ----------------------------------------------------------------------------------------------------------4V EN, ILMT, MODE, PG, LX -------------------------------------------------------------------------------------------------25V VCC, FB ----------------------------------------------------------------------------------------------------------4V BYP --------------------------------------------------------------------------------------------------------6V Power Dissipation, PD @ TA = 25°C QFN3x3-20 ------------------------------------------------------------------------------------3.3W Package Thermal Resistance (Note 2) θ JA, QFN3x3-20 -----------------------------------------------------------------------------------------------30°C/W θ JC, QFN3x3-20 ----------------------------------------------------------------------------------------------4.5°C/W Junction Temperature Range -----------------------------------------------------------------------------------------------150°C Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------------------260°C Storage Temperature Range --------------------------------------------------------------------------------------65°C to 150°C Dynamic LX voltage in 10ns duration --------------------------------------------------------------------IN+3V to GND-5V Recommended Operating Conditions (Note 3) Supply Input Voltage ---------------------------------------------------------------------------------------------------4V to 23V Junction Temperature Range ------------------------------------------------------------------------------------- - 40°C to 125°C Ambient Temperature Range --------------------------------------------------------------------------------------40°C to 85°C AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 3 SY8286A Electrical Characteristics (VIN = 12V, TA = 25°C unless otherwise specified) Parameter Input Voltage Range Input UVLO Threshold UVLO hysteresis Quiescent Current Shutdown Current Feedback Reference Voltage Top FET RON Bottom FET RON Output Discharge Current Top FET Current Limit Bottom FET Current Limit Soft Start Time EN/MODE Rising Threshold EN/MODE Falling Threshold ILMT Rising Threshold ILMT Falling Threshold Switching Frequency Min ON Time Min OFF Time VCC Output Voltage Output Over Voltage Threshold Output Over Voltage Hysteresis Output OVP Delay Output Under Voltage Protection Threshold Output UVP Delay Power Good Threshold Power Good Hysteresis Power Good Delay Symbol V V V UVLO Min 4 VIN Rising HYS IQ I SHDN V IOUT=0, VOUT=VSET*105% EN=0, 0.594 REF R DS(ON)1 R DS(ON)2 I DIS I LMT,HSFET I LMT, LSFET t ILMT=Low ILMT=Floating ILMT=High 6.7 9.3 12 SS V Typ 0.1 120 6 0.6 38 19 70 17 7.8 10.6 13.3 1.3 V CC V OVP V =V IN 510 INMAX With 1mA Lo d VFB Rising 3.2 115 57.5 20 62.5 2.97 200 92 1.5 200 10 3.1 OVP,DLY UVP t UVP,DLY V PG V PG,HYS t PG,RISING t V BYP V 600 50 150 3.3 120 0.5 690 3.4 125 VFB Falling VFB Rising (Good) Low to high High to low Unit V V V µA µA V mΩ mΩ mA A A A A ms V V V V kHz ns ns V %V REF %V 1.5 OVP,HYS V 8.9 11.9 14.8 Vcc-0.5 V t 145 10 0.606 0.4 ENL V ILMTH V ILMTL F OSC T ON,MIN T OFF,MIN V Max 23 3.9 1 ENH PG,FALLING Bypass Switch Turn -on Voltage Bypass Switch Switchov r Hysteresis Bypass Switch OVP Thermal Shutdown Temperature Thermal Shutdown hysteresis Test Conditions IN REF 67.5 µs %V REF us %V REF %V REF 3.21 µs µs V 0.15 V SD 120 150 %VCC °C THYS 15 °C BYP,HYS V BYP,OVP T 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 AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 4 SY8286A operational sections of the specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability Note 2: Package thermal resistance 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_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 5 SY8286A Typical Performance Characteristics Efficiency vs. Load Current Efficiency vs. Load Current (VBYP=3.3V, MODE=High) (VBYP=3.3V, MODE=Low) 100 100 90 90 80 80 70 60 70 50 60 40 VIN=5V,VOUT=1.2V VIN=12V,VOUT=1.2V VIN=19V,VOUT=1.2V 50 30 VIN=23V,VOUT=1.2V 40 VIN=5V,VOUT=1.2V VIN=12V,VOUT=1.2V 20 VIN=19V,VOUT=1.2V 10 30 VIN=23V,VOUT=1.2V 0 0.001 0.01 0.1 1 0.001 10 0.01 0.1 1 Load Current (A) Load Cu ent (A) Efficiency vs. Load Current Efficiency vs. Load Current 10 (VBYP=3.3V, MODE=High) (VBYP=3.3V, MODE=Low) 100 100 90 90 80 80 70 60 70 50 60 40 VIN=5V,VOUT=1.8V VIN=12V,VOUT=1.8V VIN=19V,VOUT=1.8V VIN=23V,VOUT=1.8V 50 40 30 VIN=5V,VOUT=1.8V VIN=12V,VOUT=1.8V 20 VIN=19V,VOUT=1.8V 10 30 VIN=23V,VOUT=1.8V 0 0.001 0.01 0.1 1 0.001 10 0.01 1 Load Current (A) Efficiency vs. Load Current Efficiency vs. Load Current 10 (VBYP=3.3V, MODE=High) (VBYP=3.3V, MODE=Low) 100 100 95 90 90 80 85 70 80 60 75 50 70 40 VIN=5V,VOUT=3.3V 65 30 VIN=12V,VOUT=3.3V VIN=23V,VOUT=3.3V 55 VIN=5V,VOUT=3.3V VIN=12V,VOUT=3.3V 20 VIN=19V,VOUT=3.3V 60 50 0.001 0.1 Load Current (A) VIN=19V,VOUT=3.3V 10 VIN=23V,VOUT=3.3V 0 0.01 0.1 Load Current (A) 1 10 0.001 0.01 0.1 1 10 Load Current (A) AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 6 SY8286A Efficiency vs. Load Current Efficiency vs. Load Current (VBYP=3.3V,MODE=High) (VBYP=3.3V, MODE=Low) 100 100 95 90 90 80 85 70 80 60 75 50 70 40 VIN=7.4V,VOUT=5V VIN=12V,VOUT=5V VIN=19V,VOUT=5V 65 60 VIN=23V,VOUT=5V 55 50 0.001 30 VIN=7.4V,VOUT=5V 20 VIN=12V,VOUT=5V VIN=19V,VOUT=5V VIN=23V,VOUT=5V 10 0 0.01 0.1 1 0.001 10 0.01 0.1 Load Current (A) Load Regulation 5.020 5.010 5.010 5.000 5.000 4.990 4.990 VIN=7.4V,VOUT=5V VIN=12V,VOUT=5V VIN=19V,VOUT=5V VIN=23V,VOUT=5V 4.980 4.970 1.0 2.0 3.0 4.0 5.0 6.0 4.960 0.0 VIN=19V,VOUT=5V VIN=23V,VOUT=5V 1.0 2.0 3.0 4.0 5.0 6.0 Output Current (A) Line Regulation (VBYP=3.3V, MODE=Low) 5.030 5.020 5.020 5.010 5.010 5.000 5.000 (VBYP=3.3V, MODE=High) 4.990 4.990 4.980 4.960 6.0 VIN=12V,VOUT=5V 4.970 Line Regulation 4.970 VIN=7.4V,VOUT=5V 4.980 Output Current (A) 5.030 (V BYP=3.3V, MODE=High) 5.030 5.020 4.960 0.0 10 Load Regulation (VBYP=3.3V, MODE=Low) 5.030 1 Load Current (A) 4.980 IO=0.001A, VO=5V IO=0.001A, VO=5V IO=3A, VO=5V IO=6A, VO=5V 11.0 4.970 16.0 Input Voltage (V) 21.0 23.0 4.960 6.0 IO=3A, VO=5V IO=6A, VO=5V 11.0 16.0 21.0 23.0 Input Voltage (V) AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 7 SY8286A Load Transient (VIN=12V, VOUT=3.3V, IOUT=0.6-6A, MODE=Low) ∆VOUT 100mV/div I 5A/div Load Transient (VIN=12V, VOUT=3.3V, IOUT=0.6-6A, MODE=High) ∆VOUT IL L Time (200µs/div) ∆Vo 5A/div Time (200µs/div) Output Ripple (VIN=12V, VO=3.3V, IO=0A, MODE=Low) 100mV/div Output Ripple (VIN=12V, V O=3.3V, IO=0A, MODE=High) ∆Vo 20mV/div VLX 5V/div IL 2A/div 20mV/div VLX 5V/div IL 2A/div Time (2µs/div) Output Ripple (VIN=12V, VO=3.3V, IO=3A) ∆Vo 20mV/div VLX 10V/div Time (2µs/div) Output Ripple (VIN=12V, VO=3.3V, IO=6A) ∆Vo VLX IL IL 20mV/div 10V/div 5A/div 5A/div Time (2µs/div) Time (2µs/div) AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 8 SY8286A Startup from VIN (VIN=12V, VOUT=3.3V, IO=6A) VIN Shutdown from VIN (VIN=12V, VOUT=3.3V, IO=6A) 10V/div VIN 10V/div VOUT 2V/div VOUT 2V/div VLX 10V/div VLX 10V/div IL 5A/div IL 5A/div Time (4ms/div) Time (4ms/div) Startup from Enable Shutdown f om Enable (VIN=12V, VOUT=3.3V, IO=6A) (VIN=12V, VOUT=3.3V, IO=6A) EN 5V/div EN 5V/div VOUT 2V/div VOUT 2V/div VLX 10V/div VLX 10V/div IL 5A/div IL 5A/div Time (2ms/div) Time (2ms/div) Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=3.3V, IO=0A~ Short, ILMT: Pull Low) (VIN=12V, VOUT=3.3V, IO=6A~ Short, ILMT: Pull Low) VOUT IL 2V/div 5A/div Time (4ms/div) VOUT 2V/div IL 5A/div Time (4ms/div) AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 9 SY8286A Short Circuit Protection (VIN=12V, VOUT=3.3V, IO=0A~ Short, ILMT: Floating) Short Circuit Protection (VIN=12V, VOUT=3.3V, IO=6A~ Short, ILMT: Floating) VOUT 2V/div VOUT 2V/div IL 5A/div IL 5A/div Time (4ms/div) Time (4ms/div) Short Circuit Protection Short Circuit P otection (VIN=12V, VOUT=3.3V, IO=0A~ Short, ILMT: Pull High) (VIN=12V, VOUT=3.3V, IO =6A~ Short, ILMT: Pull High) VOUT IL 2V/div 5A/div Time (4ms/div) VOUT 2V/div IL 5A/div Time (4ms/div) AN_SY8286A Rev. 0.9C Silergy Corp. Confidential- Prepared for Customer Use Only 10 SY8286A pins. In this case, a 10uF low ESR ceramic capacitor is recommended. Operation The SY8286A develops a high efficiency synchronous step-down DC-DC regulator capable of delivering 6A current. The device integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SY8286A operates over a wide input voltage range from 4V to 23V. The DC-DC regulator adopts the instant PWM architecture to achieve fast transient responses for high step down applications and high efficiency at light load. The device provides various protection features for reliable operation. In addition, it operates at pseudoconstant frequency of 600kHz to minimize the size of inductor and capacitor. Applications Information Because of the high integration in the SY8286A 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. Feedback resistor dividers R1 and R2: Choose R1 and R2 to program the proper output voltage. To minimize the power consumption under light load, it is desirable to choose large resistance values for bo h R1 and R2. A value of between 10kΩ and 1MΩ is highly recommended for both resistors. If Vout is 1.2V, R1=100k is chosen, then using following equat on, R2 can be calculated to be 100kΩ: 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. 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: L= 0.6V 0.6VFB R2 = VOUT − 0.6V R1 . GND R2 Input capacitor CIN: The ripple current through input capacitor is calculated as： ICIN _ RMS = IOUT ⋅ D(1− D) . 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 (1− V OUT OUT F ×I SW /V ) IN,MAX × 40% OUT,MAX where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SY8286A 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. ISAT , MIN > IOUT ,MAX + VOUT R1 V 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