SY7208LABC

Applications Note:AN_SY7208L High Efficiency 1MHz, 2A Step Up Regulator General Description Features The SY7208L is a high efficiency boost regulators targeted for general step-up applications. • • • • • • • • Ordering Information SY7208□(□□)□ Temperature Code Package Code Optional Spec Code Ordering Number SY7208LABC Package type SOT23-6 Wide input range: 3-25V bias input, 25Vout max 1MHz switching frequency Minimum on time: 100ns typical Minimum off time: 100ns typical Low RDS(ON): 150mΩ RoHS Compliant and Halogen Free Accurate Reference: 0.6VREF Compact package: SOT23 6 pins Applications Note 2A • WLED Drivers • Networking cards powered from PCI or PCIexpress slots Typical Applications Figure 1. Schematic Diagram AN_SY7208L Rev.0.9 Figure 2. Efficiency vs Load Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 SY7208L Pinout (top view) （SOT23-6） Top Mark: MIxyz (Device code: MI, x=year code, y=week code, z= lot number code) Pin Name IN GND LX FB Pin Number 5 2 1 3 EN 4 Pin Description Input pin. Decouple this pin to GND pin with 1uF ceramic cap. Ground pin Inductor node. Connect an inductor between IN pin and LX pin. Feedback pin. Connect a resistor R1 between VOUT and FB, and a resistor R2 between FB and GND to program the output voltage: VOUT=0.6V*(R1/R2+1). Enable control. High to turn on the part. Don’t leave it floated. NC 6 No connection. Absolute Maximum Ratings (Note 1) LX, IN, EN ---------------------------------------------------------------------------------------------------------- 26V All other pins-------------------------- ------------------------------------------------------------------------------ 4V Power Dissipation, PD @ TA = 25°C SOT23-6 ----------------------------------------------------------------- 0.6W Package Thermal Resistance (Note 2) θ JA -------------------------------------------------------------------------------------------------------- 161°C/W θ JC -------------------------------------------------------------------------------------------------------- 130°C/W Junction Temperature Range ------------------------------------------------------------------------------------ 125°C Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C Storage Temperature Range ------------------------------------------------------------------------------------- -65°C to 150°C Recommended Operating Conditions (Note 3) Input Voltage Supply----------------------------------------------------------------------------------------------- 3V to 25V Junction Temperature Range ------------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------- -40°C to 85°C AN_SY7208L Rev.0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 2 SY7208L Electrical Characteristics (VIN = 5V, VOUT=12V, IOUT=100mA, TA = 25°C unless otherwise specified) Parameter Input Voltage Range Quiescent Current Shutdown Current Low Side Main FET RON Main FET Current Limit Switching Frequency Feedback Reference Voltage IN UVLO Rising Threshold UVLO Hysteresis Thermal Shutdown Temperature EN Rising Threshold EN Falling Threshold EN Pin Input Current Max Duty Cycle Symbol VIN IQ ISHDN Rds(on) Test Conditions Min 3 VFB=0.66V EN=0 Typ Max 25 100 15 150 ILIM1 2 Fsw VREF 0.8 0.588 1 0.6 VIN,UVLO UVLO,HYS TSD VENH VENL IEN 2.6 A 1.2 0.612 MHz V 2.7 V 0.1 150 V °C 2 0.4 100 0 Unit V µA µA mΩ 90 V V nA % Note 1: Stresses beyond “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2: θ JA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Test condition: Device mounted on 2” x 2” FR-4 substrate PCB, 2oz copper, with minimum recommended pad on top layer and thermal vias to bottom layer ground plane. Note 3: The device is not guaranteed to function outside its operating conditions. Note 4: IC could be start up in 2.7V. AN_SY7208L Rev.0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 3 SY7208L Function Block AN_SY7208L Rev. 0.9 Silergy Corp. Confidential- Prepared for Internal Use Only 4 SY7208L Typical Performance Characteristics AN_SY7208L Rev. 0.9 Silergy Corp. Confidential- Prepared for Internal Use Only 5 SY7208L Output Ripple (VIN=5V, VOUT=12V,Iload=40mA) LX (5V/div) VO(AC) (0.1V/div) IL (0.5A/div) Time(4us/div) Output Ripple (VIN=5V, VOUT=12V,Iload=500mA) LX (5V/div) VO(AC) (50mV/div) IL (1A/div) Time(400ns/div) AN_SY7208L Rev. 0.9 Silergy Corp. Confidential- Prepared for Internal Use Only 6 Because of the high integration in the SY7208L IC, the application circuit based on this regulator IC is rather simple. Only input capacitor CIN, output capacitor COUT, 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 10k and 1M is recommended for both resistors. If R1=200k is chosen, then R2 can be calculated to be: R2 = (R1 × 0.6V)/(VOUT − 0.6V) VOUT 0.6VFB GND where FSW is the switching frequency and IOUT,MAX is the maximum load current. The SY7208L 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. VIN(VOUT − VIN)  VOUT  ISAT,MIN >   × IOUT_MAX + 2 × FSW × L × VOUT  VIN  R1 R2 Input capacitor CIN: The ripple current through input capacitor is calculated as: VIN ⋅ (VOUT − VIN) ICIN_RMS = 2 3 ⋅ L ⋅ FSW ⋅ VOUT 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 is recommended. 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 with 25V rating and more than two pcs 10uF capacitor. Boost 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 average input current. The inductance is calculated as: AN_SY7208L Rev. 0.9 (VOUT − VIN)  VIN  L=   VOUT  FSW × IOUT, MAX × 40% 2 Applications Information 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