SY7208CABC

Application Note:AN_SY7208C High Efficiency 1MHz, 600mA Step Up Regulator General Description Features The SY7208C is a high efficiency boost regulator targeted for general step-up applications. • • • • • • • • Ordering Information SY7208□(□□)□ Temperature Code Package Code Optional Spec Code Ordering Number SY7208CABC 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 Applications Note ---- • • WLED Drivers Networking car s powered from PCI or PCIexpress slots 2 Typical Applications Figure 1. Schematic Diagram Figure 2. Efficiency vs Load Current AN_SY7208C Rev. 0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 1 SY7208C Pinout (top view) LX 1 GND 6 IN 2 5 NC FB 3 4 EN （SOT23-6） Top Mark: JUxyz (Device code: JU, x=year code, y=week code, z= lot number code) Pin Name IN GND LX FB Pin Number 6 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 l eave it floated. NC 5 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) θJA --------------------------------------------------------------------------------------------------------161°C/W θJC --------------------------------------------------------------------------------------------------------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_SY7208C Rev. 0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 2 SY7208C 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 Symbol V IN I Q I SHDN Test Conditions Min 3 VFB=0.66V EN=0 LIM1 Fsw V REF V 0.8 0.588 U VLO,HYS T 1 0.6 1.2 0.612 MHz V 2.3 V V °C 2 0 Unit V µA µA mΩ mA 0.1 150 SD EN 5 600 IN,UVLO V ENH V ENL I Max 25 100 1 150 Rds(on) I Typ 0.4 100 V V nA Note 1: Stresses beyond “Absolute Maximum Ratings” m y ca use permanent damage to the device. These are for stress ratings. Functional operation of the device at hese 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: 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. Test condition: Device mounted on 2” x 2” FR-4 substrate PCB, 2oz copper, with minimum rec mmended 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_SY7208C Rev. 0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 3 SY7208C Typical Performance Characteristics Load Transient (VIN=5V, VOUT=12V, ILOAD=0.05-0.3A) Efficiency (%) VOUT(AC) IO 0.1V/div 0.1A/div Time (100µs/div) Shutdown from VIN VIN (VIN=5.0V, VOUT=12V, IOUT=0.3A) 2V/div VOUT 5V/div Io 0.2A/div Time (2ms/div) Startup from Enable (VIN=5.0V, VOUT=12V, IOUT=0.3A) EN 2V/div VOUT 5V/div Io 0.2A/div Time (200µs/div) AN_SY7208C Rev. 0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 4 SY7208C Output Ripple (VIN=5.0V, VOUT=12V, IOUT=20mA) VOUT(AC) 10mV/div IO 0.2A/div VLX 5V/div Time (400ns/div) AN_SY7208C Rev. 0.9 Silergy Corp. Confidential- Prepared for Customer Use Only 5 SY7208C Applications Information Because of the high integration in the SY7208C 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 R2=120k is chosen, then R1 can be calculated to be: R1 = (VOUT − 0.6V) × R2 0.6V ⎛ VIN ⎞ L=⎜ 2 ⎟ (VOUT − VIN) ⎝ VOUT ⎠ FSW × IOUT, MAX × 40% where FSW is the switching frequency and IOUT,MAX is the maximum load current. The SY7208C 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. ⎛ VOUT ⎞ ISAT, MIN > ⎜ ⎟ ⎝ VIN ⎠ 2 ⎛ VIN ⎞ (VOUT − VIN) × IOUT, MAX + ⎜ ⎟ ⎝ VOUT ⎠ 2 × FSW × L Input capacitor CIN: The ripple current through input capacitor is calculated as: I CIN_RMS = VIN ⋅ (VOUT − VIN) 2 3 ⋅ L ⋅ FSW ⋅ VOUT To minimize the potential noise problem, place a typical X7R or better grade ceramic capacitor really close to the IN and GND pins. Care should be taken o minimize the loop area formed by CIN, and IN/GND pins. Output capacitor COUT: The output capacitor is selected to ha dle 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 X7R or better grade ceramic capacitor with 25V rating and greater than 10uF capacitance. 3) The DCR of the inductor and the core loss at the switching frequency must be low enough to achi ve the desired efficiency requirement. It is desirable to choose an inductor with DCR