SY8205FCC

Application Notes: AN_SY8205 High Efficiency Fast Response，5A, 30V Input Synchronous Step Down Regulator Preliminary Specification General Description Features SY8205 develops a high efficiency synchronous stepdown DC-DC converter capable of delivering 5A output current. SY8205 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. • SY8205 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 500kHz under continous conduction mode to minimize the size of inductor and capacitor. Ordering Information SY8205 ( □ □□ □ ) Temperature Code Package Code Optional Spec Code Temperature Range: -40°C to 85°C Ordering Number SY8205DNC SY8205FCC Package type DFN4×3-12 SO8E • • • • • • • • • • • Low RDS(ON) for internal switches (top/bottom): 70/40 mΩ 4.5-30V input voltage range Instant PWM architecture to achieve fast transient responses External softstart limits the inrush current Pseudo-constant frequency: 500kHz at heavy loads 5A continuous, 6A peak load current capability 1.5% 0.6V reference Output over current limit Output short circuit protection with current fold back Thermal shutdown and auto recovery RoHS Compliant and Halogen Free Com act package: DFN3x4-12/SO8E Applications Note --- • • • • • • LCD-TV SetTop Box Notebook Storage High power AP router Networking Typical Applications Figure 1. Schematic Diagram Figure(SY8205DNC) AN_SY8205 Rev. 0.4 Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY8205 Figure 2. Schematic Diagram Figure(SY8205FCC) Efficiency vs. Load Current 100 90 80 12VIN,5VOUT 70 18VIN,5VOUT 30VIN,5VOUT 60 0 1 2 3 Load Current (A) 4 5 Figure 3. Efficiency vs. Load Current AN_SY8205 Rev. 0.4 Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY8205 Pinout (top view) (DFN4x3-12) (SO8E) Top Mark: ADSxyz, (Device code: ADS, x=year code, y=week code, z= lot number code) Top Mark: AHHxyz, (Device code: AHH, x=year code, y=week code, z= lot number code) Pin Name Pin Number 1 1 SVIN Exposed Paddle 10 Exposed Paddle / PVIN 11,12 7,8 LX 2,3,4 2 EN 5 3 VCC 9 6 PG 6 / FB 7 5 SS 8 4 BS GND AN_SY8205 Rev. 0.4 Pin Description Boot-Strap Pin. Supply high side gate driver. Decouple this pin to LX pin with 0.1uF ceramic cap. Ground pin. Analog supply input. Bypass 1uF capacitor to ground. Power supply input. Decou le this pin to GND pin with at least 10uF ceramic cap Inductor pin. Connect this pin to the switching node of inductor Enable control. The device has an accurate 1.2V rising threshold that will allow the user to program the accurate turn-on delay by adding RC before the EN pin. Internal 3.3V LDO output. Power supply for internal analog circuits and driving circuit. Add a 1uF bypass capacitor to GND. Power good indicator. Open drain output if the output is within 90% of regulation; low otherwise. 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) Softstart programming pin. Connect a capacitor from this pin to ground to program the softstart time. Tss=Css*0.6V/10uA Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY8205 Absolute Maximum Ratings (Note 1) PVIN, SVIN, LX, BS, EN, PG ----------------------------------------------------------------------------------------------VCC,FB, SS, BS-LX ------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C DFN4X3-12/SO8E ----------------------------- ------------------------------Package Thermal Resistance (Note 2) θ JA ------------------------------------------------------------------------------------------------------------θ JC ------------------------------------------------------------------------------------------------------------Junction Temperature Range -----------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------- 33V 4V 2.8/3.3W 36/30°C/W 18°/10C/W 125°C 260°C -65°C to 150°C Recommended Operating Conditions (Note 3) Supply Input Voltage -------------------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------Ambient Temperature Range -------------------------------------------------------------------------------------- 4.5V to 30V -40°C to 125°C -40°C to 85°C Function Block AN_SY8205 Rev. 0.4 Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY8205 Electrical Characteristics (VIN = 12V, VOUT = 5V, COUT = 47uF, TA = 25°C, I OUT = 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 Test Conditions IN IQ I SHDN V IOUT=0, VFB=VREF*105% EN=0 I V =V 0.591 REF FB Min 4.5 FB CC Typ 200 5 0.6 -50 Rds(on)1 Rds(on)2 V ENL V 1.1 EN,HYS V 1.2 0.1 V VCC T nA mΩ mΩ A 1.3 V V V V kHz ns ns V °C 4 UVLO IOUT=200mA VIN=4V 3.2 SD T SD,HYS 0.2 500 80 120 3.3 160 Unit V µA µA V 50 5 LIM OSC 10 0.609 70 40 I V HYS F Max 30 3.4 20 °C Note 1: Stresses beyond the “Absolute Maximum Rati gs” ma y 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 mplied. 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 DFN3x3-12/SO8E packages is the case position for θJC measurement. Note 3: The device is n t guaranteed to function outside its operating conditions. AN_SY8205 Rev. 0.4 Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY8205 Typical Performance Characteristics Ef fic ie nc y ( % ) Efficiency (%) Ef fic ie nc y ( % ) AN_SY8205 Rev. 0.4 Silergy Corp. Confidential- Prepared for Customer Use Only 6 AN_SY8205 Shutdown (EN=10Hz,VIN=12V, VOUT=5V, ILOAD=5A) EN 5V/div VLX 10V/div VOUT 5V/div IL 5A/div Time (400µs/div) AN_SY8205 Rev. 0.4 Short Circuit Protection (VIN=12V, VOUT=5V, Null load to Short) VOUT 5V/div IL 2A/div Time (1ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 7 AN_SY8205 Operation pins. In this case, a 10uF low ESR ceramic capacitor is recommended. SY8205 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. SY8205 provides protection functions such as cycle by cycle current limiting and thermal shutdown protection. SY8205 will sense the output voltage conditions for the fault protection. Applications Information Because of the high integration in the SY8205 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 F ×I SW /V OUT ) IN, MAX × 40% OUT, MAX where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SY8205 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