SY8204FCC

Application Notes: AN_SY8204 High Efficiency Fast Response, 4A, 30V Input Synchronous Step Down Regulator General Description Features SY8204 develops a high efficiency synchronous stepdown DC-DC converter capable of delivering 4A output current. SY8204 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. • SY8204 adopts the proprietary 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 500kHz under continous conduction mode to minimize the size of inductor and capacitor. Ordering Information SY8204 ( □ □□ □ ) Temperature Code Package Code Optional Spec Code Temperature Range: -40°C to 85°C Ordering Number SY8204FCC Package type SO8E • • • • • • • • • • • Low RDS(ON) for internal switches (top/bottom): 80/50 mΩ 4.5-30V input voltage range Instant PWM architecture to achieve fast transient responses External softstart limits the inrush curre t Pseudo-constant frequency: 500kHz at heavy loads 4A continuous, 5A peak load current capability 1.5% 0.6V reference Output over current limit Output short circuit p otection with current fold back Thermal shut own and auto recovery RoHS Compliant and Halogen Free Compact package: SO8E Applications Note -- • • • • • • • LCD-TV SetTop Box Notebook High power AP router LCD Monitor DVR/NVR NAS Typical Applications Efficiency vs. Load Current 90 Efficiency (%) 85 80 75 70 65 60 VIN=12V, VOUT=1.8V VIN=18V, VOUT=1.8V 55 VIN=30V, VOUT=1.8V 50 1 Figure 1. Schematic Diagram AN_SY8204 Rev. 0.1 10 100 1000 Load Current (mA) 10000 Figure 2. Efficiency vs. Load Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY8204 Pinout (top view) Top Mark: AHIxyz (device code: AHI, x=year code, y=week code, z= lot number code) Pin Name Pin Number EN BS 3 1 LX VCC 2 6 VIN 7,8 FB 5 GND Exposed Paddle SS 4 Pin Description Enable control. Boot-Strap Pin. Supply high side gate driver. Decouple his pin to LX pin with 0.1uF ceramic cap. Inductor pin. Connect this pin to the switching node of inductor Internal 3.3V LDO output. Power supply for internal analog circuits and driving circuit. Add a 1uF bypass capacitor between this pin and GND. Voltage Supply Pin. Decouple this pin to GND pin with at least 4.7uF ceramic cap. 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) Ground pin. Softstart programming pin. Connect a capacitor from this pin to ground to program the softst rt time. Tss=Css*0.6V/10uA Absolute Maximum Ratings (Note 1) VIN, LX, BS, EN----------------------------------------------------------------------------------------------33V VCC, FB, SS, BS-LX -----------------------------------------------------------------------------------------4V Power Dissipation, PD @ TA = 25°C SO8E---------------------------------------- ---------------------------------------3.3W Package Thermal Resistance (Note 2) θ JA --------------------------------------------------------------------------------------------------------------30°C/W θ JC --------------------------------------------------------------------------------------------------------------10°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 -------------------------------------------------------------------------------------------------4.5V to 30V 40°C to 125°C Junction Temperature Range ------------------------------------------------------------------------------------- Ambient Temperature Range --------------------------------------------------------------------------------------40°C to 85°C AN_SY8204 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY8204 Electrical Characteristics (VIN = 12V, VOUT = 5V, COUT = 47uF, TA = 25°C, IOUT = 1A unless otherwise specified) Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current Top FET RON Bottom FET RON Bottom FET Current Limit EN falling threshold EN threshold hysteresis Input UVLO threshold UVLO hysteresis Oscillator Frequency Min ON Time Min OFF Time Internal LDO Output Thermal Shutdown Temperature Thermal Shutdown Hysteresis Symbol V IN I Q I SHDN V Test Conditions IOUT=0, VFB=VREF*105% EN=0 0.591 REF I FB R DS(ON)1 R DS(ON)2 I Min 4.5 V =V FB CC Typ 200 5 0.6 -50 1.1 EN,HYS V 1.2 0.1 V VCC T nA mΩ mΩ A 1.3 V V V V MHz ns ns V °C 4 UVLO IOUT=200mA VIN=4V 3.2 SD T SD,HYS 0.2 0.5 80 120 3.3 160 Unit V µA µA V 50 5 V ENL V OSC 10 0.609 80 50 LIM V HYS F Max 30 3.4 20 °C Note 1: Stresses beyond the “Absolute Maximum Ratings” ma y cause permanent damage to the device. These are stress ratings only. Functional operation of the evice 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: θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal con ductivity test board of JEDEC 51-3 thermal measurement standard. Paddle of SO8E packages is the case position for θJC measurement. Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8204 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY8204 Function Block AN_SY8204 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY8204 Efficiency (%) Efficiency (%) Typical Performance Characteristics AN_SY8204 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY8204 Short Circuit Protection SH RT CIRCUIT PROTECTION (VIN=12V, VOUT=1.8V, Open to Short) VOUT 2V/div IL 2A/div (VIN=12V, VOUT=1.8V, 4A TO SHORT) VOUT 2V/DIVOUT IL 2A/DIV IL Time (2ms/div) AN_SY8204 Rev. 0.1 5V/DIV 2A/DIV TIME (2MS/DIV) Silergy Corp. Confidential- Prepared for Customer Use Only 6 AN_SY8204 Operation pins. In this case, a 10uF low ESR ceramic capacitor is recommended. SY8204 is a synchronous buck regulator IC that integrates the PWM control, top and bottom switches on the same die to minimize the switching transition loss and conduction loss. With ultra low Rds(on) power switches and proprietary PWM control, this regulator IC can achieve the highest efficiency and the highest switch frequency simultaneously to minimize the external inductor and capacitor size, and thus achieving the minimum solution footprint. 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 47uF capacitance. SY8204 provides protection functions such as cycle by cycle current limiting and thermal shutdown protection. SY8204 will sense the output voltage conditions for the fault protection. Applications Information Because of the high integration in the SY8204 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 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: Output inductor L: There are several considerations in choos ng 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= (1 − V V OUT /V OUT F ×I SW ) IN, MAX × 40% OUT, MAX where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SY8204 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 (1-VOUT/VIN,MAX) 2 ⋅ FSW ⋅ L VOUT R2 = 0.6V V OUT R1 R1 . 0.6VFB − 0.6V GND R2 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