SY8253AIC

Application Note: SY8253 High Efficiency, 500kHz, 3A, 23V Input Synchronous Step Down Regulator General Description Features The SY8253 is a high efficiency 500 kHz synchronous step-down DC-DC converter capable of delivering 3A current. The SY8253 operates over a wide input voltage range from 4.5V to 23V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss.  Low output voltage ripple and small external inductor and capacitor sizes are achieved with 500 kHz switching frequency. It adopts the instant PWM architecture to achieve fast transient responses for high step down applications       Ordering Information SY8253 □(□□)□ Package type TSOT23-8 TSOT23-6 Internal softstart limits the inrush current Hic-cup mode output short circuit protection ±1.5% 0.6V reference Power good indicator (SY8253AIC only) TSOT23-8/ TSOT23-6 package Applications Temperature Code Package Code Optional Spec Code Ordering Number SY8253AIC SY8253ADC     low RDS(ON) for internal switches (top/bottom): 105mΩ/50mΩ 4.5-23V input voltage range 3A output current capability 500 kHz switching frequency Instant PWM architecture to achieve fast transient responses. Cycle-by-cycle peak current limitation Note ---      Set Top Box Portable TV Access Point Router DSL Modem LCD TV Typical Applications Figure 1. Schematic Diagram (SY8253AIC) AN_SY8253 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 1 SY8253 Figure 2. Schematic Diagram (SY8253ADC) AN_SY8253 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 2 SY8253 Pinout (top view) BS LX IN GND FB (TSOT23-8) Part Number SY8253AIC SY8253ADC EN (TSOT23-6) Top Mark XUxyz XTxyz Package type TSOT23-8 TSOT23-6 ① Note① ： x=year code, y=week code, z= lot number code. Pin Name BS TSOT23-8 TSOT23-6 Pin Description 1 1 GND 2 2 FB 3 3 SS 4 / PG 5 / EN 6 4 Enable control. Pull high to turn on. Do not float. IN LX 7 8 5 6 Input pin. Decouple this pin to GND pin with at least 1uF ceramic cap Inductor pin. Connect this pin to the switching node of inductor Boot-Strap Pin. Supply high side gate driver. Decouple this pin to LX pin with 0.1uF ceramic cap. Ground pin 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/4uA. Leave this pin open for default 1ms soft-start. Power good Indicator. Open drain output. Absolute Maximum Ratings (Note 1) Supply Input Voltage------------------------------------------------------------------------------------------------------------------ V BS-LX, SS------------------------------------------------------------------------------------------------------------------------------- V All other pins---------------------------------------------------------------------------------------------------------------- VIN + 0.3V Power Dissipation, PD @ TA = 25°C, TSOT23-8 /TSOT23-6----------------------------------------------------------- 1.5W Package Thermal Resistance (Note 2) θ JA------------------------------------------------------------------------------------------------------------------------ 66°C /W θ JC------------------------------------------------------------------------------------------------------------------------ 15°C /W Junction Temperature Range---------------------------------------------------------------------------------------------------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 23V Junction Temperature Range----------------------------------------------------------------------------------------- 40°C to 125°C Ambient Temperature Range------------------------------------------------------------------------------------------ 40°C to 85°C AN_SY8253 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 3 SY8253 Electrical Characteristics (VIN = 12V, VOUT =3.3V, L = 4.7uH, 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 Top FET Peak Current Limit Bottom FET RON Bottom FET Valley Current Limit EN Rising Threshold EN Falling Threshold Power Good Threshold Symbol VIN IQ ISHDN VREF Test Conditions IFB RDS(ON)1 ILIM,TOP VFB=3.3V Power Good Delay Time TPG_F TPG_R TOVP Output OVP Response Time Output OVP Off Time Soft-start Charging Current Short Circuit Protection Wait Time Short Circuit Protection Off Time Input UVLO Threshold Input UVLO Hysteresis Min ON Time Min OFF Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis IOUT=0, VFB=VREF*105% EN=0 RDS(ON)2 ILIM,BOT VENH VENL VPG Min 4.5 0.591 -50 Typ 100 5 0.6 5.1 105 6 3.0 50 3.7 1.5 VFB falling, PG from high to low VFB rising, PG from low to high VFB rising, PG from high to low VFB falling, PG from low to high PG falling edge PG rising edge 90 95 115 110 10 60 10 Max 23 10 0.609 50 Unit V µA µA V 6.9 nA mΩ A 4.5 mΩ A 0.4 V V %VREF %VREF %VREF %VREF µs µs µs tOFF,OVP ISS 1000 4 µs µA tWAIT,SCP 1.9 ms tOFF,SCP 15 ms VUVLO VHYS TSD 0.3 80 160 150 THYS 15 4.5 V V ns ns ℃ ℃ 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 Evaluation Board. Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8253 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 4 SY8253 Block Diagram (SY8253AIC) IN Current Sense Internal Power BS Input UVLO 4.5V PWM Control & Protect Logic EN 1.5V FB 0.6V LX Current Sense Internal SST Thermal Protection GND (SY8253ADC) AN_SY8253 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 5 SY8253 Typical Performance Characteristics Efficiency vs. Load Current Efficiency vs. Load Current 100 100 90 90 80 80 70 70 60 60 50 50 40 40 V IN=7V,V OUT=5V V IN =12V,V OUT =5V V IN =19V,V OUT =5V V IN =23V,V OUT =5V 30 20 V IN =5V,V OUT =3.3V V IN =12V,V OUT=3.3V V IN =19V,V OUT =3.3V V IN =23V,V OUT =3.3V 30 20 10 10 0 0 1 10 100 1000 10000 1 10 100 1000 10000 Load Current (mA) Load Current (mA) Efficiency vs. Load Current 100 90 80 70 60 50 40 30 V IN =5V,V OUT=1.2V V IN =12V,V OUT =1.2V V IN =19V,V OUT =1.2V V IN =23V,V OUT =1.2V 20 10 0 1 10 100 1000 10000 Load Current (mA) AN_SY8253 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 6 SY8253 Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=3.3V, 0A to Short) (VIN=12V, VOUT=3.3V, 3A to Short) VOUT IL 2V/div 2A/div Time (10ms/div) AN_SY8253 Rev.0.9 VOUT IL 2V/div 2A/div Time (10ms/div) Silergy Corp. Confidential-prepared for Internal Use Only 7 SY8253 Operation The SY8253 is a high efficiency 500 kHz synchronous step-down DC-DC converter capable of delivering 3A current. The SY8253 operates over a wide input voltage range from 4.5V to 23V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. Low output voltage ripple and small external inductor and capacitor sizes are achieved with 500 kHz switching frequency. It adopts the instant PWM architecture to achieve fast transient responses for high step down applications 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 22uF capacitance. Output inductor L: There are several considerations in choosing this inductor. 1) Applications Information 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 VOUT (1  VOUT /VIN,MAX ) Because of the high integration in the SY8253 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. where Fsw is the switching frequency and IOUT,MAX is the maximum load current. 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: 2) The SY8253 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. V 0.6V  0.6V R1 . 0.6VFB R1 OUT GND R2 Input capacitor CIN: The ripple current through input capacitor is calculated as： I CIN _ RMS  I OUT  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 pins. In this case, a 10uF low ESR ceramic capacitor is recommended. AN_SY8253 Rev.0.9 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 R2  FSW  IOUT, MAX  40% 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