SY7208ABC

Applications Note:AN_SY7208 High Efficiency 1MHz, 2A Step Up Regulator Preliminary Specification General Description Features The SY7208 is a high efficiency, with an integrated NMOSFET current-mode and fixed frequency boost converter. The SY7208 integrated a very low Rds-on of NMOSFTET and feedback voltage to reduce power loss and achieve high efficiency. 1MHz operate frequency and internal compensation network minimizes as few external component counts and small L and C value. SOT23-6 package provides the best solution for PCB space saving and total BOM cost. • • • • • • • • • • • SY7208□(□□)□ r fo pa Applications re Temperature Code Package Code Optional Spec Code Temperature Range: -40°C to 85°C White LED Display Backlighting Cell Phone and Smart Phone PDA, PMP, MP3 Digital Camera Note 2A en Package type SOT23-6 tia l-P • • • • on f id Ordering Number SY7208ABC d re Ordering Information Wide input range: 3-25V bias input, 25Vout max 1MHz switching frequency Low RDS(ON): 150mΩ Up to 90% efficiency Under-Voltage lockout Protection Over-Temperature Protection Internal Soft Start 1uA Shutdown current RoHS Compliant and Halogen Free Accurate Reference: 0.6VREF Compact package: SOT23-6 Sil er gy Co rp .C Typical Applications Figure 1. Schematic Diagram AN_SY7208 Rev.0.95B Figure 2. Efficiency vs Load Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY7208 Pinout (top view) (SOT23-6) Top Mark: CAxyz (Device code: CA, x=year code, y=week code, z= lot number code) SOT23-6 5 2 1 FB 3 EN NC 4 6 Pin Description Power Input pin. 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. No connection. pa re d fo r Pin Name IN GND LX Sil er gy Co rp .C on f id en tia l-P re Block Diagram AN_SY7208 Rev.0.95B Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY7208 Absolute Maximum Ratings (Note 1) LX, IN, EN ---------------------------------------------------------------------------------------------------------- 26V All other pins-------------------------- ------------------------------------------------------------------------------ 6V Power Dissipation, PD @ TA = 25°C SOT23-6 ----------------------------------------------------------------- 0.6W Package Thermal Resistance (Note 2) θ JA -------------------------------------------------------------------------------------------------------- 170°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 ESD Susceptibility (Note 2) HBM (Human Body Mode) ---------------------------------------------------------------------------------------2kV MM (Machine Mode) ---------------------------------------------------------------------------------------------- 200V Dynamic LX voltage in 50ns duration --------------------------------------------------------------------- IN+3V to GND-4V r Recommended Operating Conditions (Note 3) Sil er gy Co rp .C on f id en tia l-P re pa re d fo Input Voltage Supply ------------------- --------------------------------------------------------------------------- 3V to 25V Junction Temperature Range ------------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------- -40°C to 85°C AN_SY7208 Rev.0.95B Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY7208 Electrical Characteristics (VIN = 5V, VOUT=12V, IOUT=100mA, TA = 25°C unless otherwise specified) 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 r VIN,UVLO d fo UVLO,HYS TSD re pa re 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 % l-P 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 id en tia Note 1: Stresses listed as the above “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 for extended periods may remain possibility to affect device reliability. .C on f 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. Co rp Note 3: The device is not guaranteed to function outside its operating conditions. Sil er gy Note 4: IC can start up in 2.7V. AN_SY7208 Rev.0.95B Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY7208 Sil er gy Co rp .C on f id en tia l-P re pa re d fo r Typical Performance Characteristics AN_SY7208 Rev. 0.95B Silergy Corp. Confidential- Prepared for Internal Use Only 5 AN_SY7208 Output Ripple (VIN=5V, VOUT=12V,Iload=40mA) LX (5V/div) VO(AC) (0.1V/div) IL (0.5A/div) Time(4us/div) fo r Output Ripple re d (VIN=5V, VOUT=12V,Iload=500mA) pa LX re (5V/div) l-P VO(AC) tia (50mV/div) IL id en (1A/div) Sil er gy Co rp .C on f Time(400ns/div) AN_SY7208 Rev. 0.95B Silergy Corp. Confidential- Prepared for Internal Use Only 6 AN_SY7208 Applications Information Because of the high integration in the SY7208 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. 2 (VOUT − VIN)  VIN  L=  V F SW × IOUT, MAX × 40% OUT   where FSW is the switching frequency and IOUT,MAX is the maximum load current. The SY7208 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. r 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: 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: 2) The saturation current rating of the inductor must be selected to be greater than the peak inductor current under full load conditions. fo R2 = (R1 × 0.6V)/(VOUT − 0.6V) d VOUT re R1 VIN(VOUT − VIN)  VOUT  ISAT,MIN >   × IOUT_MAX + 2 × FSW × L × VOUT  VIN  pa 0.6VFB re 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