SY7203DBC

Application Note:AN_ SY7203 30V High Current Boost LED Driver Target Design Specification General Description Features SY7203 develops a step-up DC/DC converter that delivers an accurate constant current for driving LEDs. Operating at a fixed switching frequency of 1MHz allows the device to be used with small value external ceramic capacitors and inductor. The LED current is programmable through the external resistor. The device also supports PWM dimming for accurate LED current control. • • • • SY7203 is ideal for driving up to eight white LEDs in series or up to 30V. Ordering Information • • • • • Input voltage range: 2.8 to 30V Switch current limit: 4A Drives LED strings up to 30V 1MHz fixed frequency minimizes the external components 20kHz~1MHz wide dimming frequency range for EN/PWM pin Internal softstart limits the inrush current Open LED over voltage protection RoHS Compliant and Halogen Free Compact package: DFN3X3-10 Applications SY7203 □(□□)□ • GPS Navigation Systems • Handheld Devices • Portable Media Players Temperature Code Package Code Optional Spec Code Temperature Range: -40°C to 85°C Ordering Number SY7203DBC Package type DFN3X3-10 Note Typical Applications Figure 1. Schematic Diagram SY7203 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY7203 Pinout (top view) (DFN3X3-10) Top mark： NZxyz (Device code: NZ, x=year code, y=week code, z= lot number code) Pin Name DFN3X3-10 Pin Description LX 4, 5 Inductor node. Connect an inductor from power input to LX pin. GND Exposed Paddle Ground pin FB 2 Feedback pin. Connect a resistor RFB between FB and GND to program the output current: ILED=0.2V/RFB. EN/PWM 9 Enable and dimming control. Pull high to turn on IC. The recommend dimming frequency range is 20kHz~1MHz. OVP 8 IN 7 NC 1, 3, 6, 10 Over voltage protection input. Connect to the output of circuit. The typical OVP value is 30V. Input pin. Decouple this pin to GND pin with 1uF ceramic cap. No connection Absolute Maximum Ratings IN, EN/PWM ----------------------------------------------------------------------------------------------------------------- 32V LX, OVP ---------------------------------------------------------------------------------------------------------------------- 36V All other pins ------------------------------------------------------------------------------------------------------------------- 4V Power Dissipation, PD @ TA = 25°C, DFN3X3-10 ----- -------------------------------------------------------------2.6 W Package Thermal Resistance (Note 2) DFN3X3-10, θJA ----------------------------------------------------------------------------------------------38°C/W DFN3X3-10, θJC -----------------------------------------------------------------------------------------------8°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 Input Voltage Supply ---------------------------------------------------------------------------------------------- 2.8V to 30V Junction Temperature Range ---------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------ -40°C to 85°C AN_SY7203 Rev. 1 Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY7203 Electrical Characteristics (VIN = 3.6V, TA = 25°C, unless otherwise specified) Parameter Symbol Conditions Min Typ Max Unit Input Voltage Range VIN 2.8 30 V Quiescent Current IQ VFB=0.3V 100 200 µA Shutdown Current ISHDN EN=0 10 15 µA Feedback Reference Voltage VREF 196 200 204 mV FB Input Current IFB VFB=0.3V 1 µA Low Side Main FET RON RDS(ON)1 100 mΩ Main FET Current Limit ILIM1 4 A EN Rising Threshold VENH 1.5 V EN Falling Threshold VENL 0.4 V IN UVLO Rising Threshold VIN,UVLO 2.4 V UVLO Hysteresis UVLO,HYS 0.2 V Switching Frequency FSW 0.8 1 1.2 MHz Minimum ON Time TON,MIN 100 nS Maximum Duty Cycle DMAX 90 % OVP Threshold VOVP Open LED 30 V Thermal Shutdown TSD 150 °C Temperature Thermal Hysteresis THYS 20 °C 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: 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. AN_SY7203 Rev. 1 Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY7203 Typical Performance Characteristics (VIN=5V, ILED=0.3A, 5PCS LED Series) Efficiency vs. Input Voltage 96 LED Current (mA) 95 94 93 92 91 90 4 6 8 10 12 Input Voltage (V) Quiescent Current vs. Input Voltage 190 180 170 160 150 140 3 6 9 12 15 18 21 24 27 30 Input Voltage (V) AN_SY7203 Rev. 1 Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY7203 AN_SY7203 Rev. 1 Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY7203 Applications Information Because of the high integration in the IC, the is simple. Only input capacitor CIN, output capacitor COUT, inductor L, Schottky diode D and sense resistors R1 need to be selected for the targeted applications specifications. Sense resistor R1 : Choose R1 to program the proper LED Current. The R1 can be calculated to be: 0.2 I LED ILED is the average LED current. R1 = Input capacitor CIN: The ripple current through input capacitor is calculated as: ICIN_RMS = VIN ⋅ (VOUT − VIN) 2 3 ⋅ L ⋅ FSW ⋅ VOUT An X5R or better grade ceramic capacitor with capacitance larger than 4.7uF is recommended to handle this ripple current. Place this ceramic capacitor really close to the IN and GND pins to minimize the potential noise problem. Care should be taken to minimize the loop area formed by CIN, and IN/GND pins. Output capacitor COUT: The output capacitor is selected to handle the output ripple noise requirements. This ripple voltage is related to the capacitor’s capacitance and its equivalent series resistance (ESR). For the best performance, it is recommended to use X5R or better grade low ESR ceramic capacitor. The voltage rating of the output capacitor should be higher than the maximum output voltage. The minimum required capacitance can be calculated as: COUT = IOUT, MAX ⋅ (VOUT − VIN) FSW ⋅ VOUT ⋅ VRIPPLE VRIPPLE is the peak to peak output ripple. For LED applications, the equivalent resistance of the LED is typically low. The output capacitance should be large enough to attenuate the ripple current through LED. A capacitor larger than 2.2uF is recommended. AN_SY7203 Rev. 0.1 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 average input current. The inductance is calculated as: (VOUT − VIN)  VIN  L=   VOUT  FSW × IOUT, MAX × 40% 2 where FSW is the switching frequency and IOUT,MAX is the maximum load current. The SY7203 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   VIN  (VOUT − VIN) ISAT, MIN >   × IOUT, MAX +    VIN   VOUT  2 × FSW × L 2 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