SY7301AADC

Application Note: AN_SY7301A 40V High Current Boost LED Driver General Description Features SY7301A 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. LEDs connected in series are driven with a regulated current set by the external resistor. The SY7301A is ideal for driving up to ten white LEDs in series or up to 40V. • • • • Ordering Information • • • • • Input voltage range: 2.8 to 40V Switch current limit:2A Drives LED strings up to 40V 1MHz fixed frequency minimizes the external components 200Hz~1MHz dimming frequency for EN/PWM pin Internal softstart limits the inrush current Open LED over voltage protection RoHS Compliant and Halogen F ee Compact package: TSOT23 -6/DFN3X3-10 SY7301 □(□□)□ Temperature Code Package Code Optional Spec Code Ordering Number SY7301AADC SY7301ADBC Package type TSOT23-6 DFN3X3-10 Applications • • • GPS Navigation Systems Handheld Devices Portable Media Players Note ------- Typical Applications Efficiency vs. Input Voltage Outpu Load:10PCS LEDs(Vout=30V),ILED=20mA 91%  90%  89%  88%  87%  86%  Input Voltage (V) Figure 1. Schematic Diagram AN_SY7301A Rev. 0.9B Figure 2. Efficiency Figure Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY7301A Pinout (top view) W G xy z (DFN3X3-10) （TSOT23-6） Top Mark: WGxyz for SY7301AADC (Device code: WG, x=year code, y=week code, z= lot number code) WRxyz for SY7301ADBC (Device code: WR, x=year code, y=week code, z= l t number code) Pin Name LX TSOT23-6 1 DFN3X3-10 4, 5 GND FB 2 3 11(Exposed Paddle) 2 EN/PWM 4 9 OVP 5 8 IN 6 7 NC 6 1, 3, 6, 10 Pin Description Inductor node. Connect an inductor from power input to LX pin. Ground pin. Feedback pin. Connect a resistor RFB between FB and GND to program the output current: ILED=0.3V/RFB. Enable and dimming control. Pull high to turn on IC. When used as dimming input, the first pulse should be longer than 200ns to turn on IC, and then shorter than 100nS to turn off IC. The recommend dimming frequency range is 200Hz~1MHz. Over voltage protection input. Connect to the output of circuit. The typical OVP value is 37V. Input pin. Decouple this pin to GND pin with 1uF or more ceramic cap. No connection Absolute Maximum Ratings (Note 1) LX, IN, EN,OVP -------------------------------------------------------------------------------------------------------------42V All other pins-------------------------------------------------------------------------------------------------------------------4V Power Dissipation, PD @ TA = 25°C TSOT23-6/DFN3X3-10 --------------------------------------------------0.6/2.6W Package Thermal Resistance (Note 2) TSOT23-6/DFN3X3-10, θ JA --------------------------------------------------------------------------- 208/48°C/W TSOT23-6/DFN3X3-10, θ JC ----------------------------------------------------------------------------130/8°C/W Junction Temperature Range --------------------------------------------------------------------------------------------150°C Lead Tempe ature (Soldering, 10 sec.) --------------------------------------------------------------------------------260°C Storage T mperature Range ----------------------------------------------------------------------------------- - 65°C to 150°C Recommended Operating Conditions (Note 3) Input Voltage Supply------------------------------------------------------------------------------------------------ 2.8V to 40V Junction Temperature Range ---------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ----------------------------------------------------------------------------------- -40°C to 85°C AN_SY7301A Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY7301A Electrical Characteristics (VIN = 3.6V, TA = 25°C, unless otherwise specified) Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current Low Side Main FET RON Main FET Current Limit EN Rising Threshold EN Falling Threshold PWM Dimming Frequency IN UVLO Rising Threshold UVLO Hysteresis Switching Frequency Minimum ON Time Maximum Duty Cycle OVP Threshold Thermal Shutdown Temperature Thermal Hysteresis Symbol VIN IQ ISHDN VREF IFB RDS(ON)1 ILIM1 VENH VENL Test Conditions Min 2.8 VFB=0.3V EN=0 294 VFB=0.3V Typ 100 10 300 Max 40 200 15 306 1 200 2 1.5 0.4 1000 2.7 0.2 VIN,UVLO UVLO,HYS FSW TON,MIN DMAX VOVP TSD THYS 0.8 Open LED 35 0.1 1 100 95 37 150 20 1.2 39 Unit V µA µA mV µA mΩ A V V kHz V V MHz nS % V °C °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: 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. Block Diagram IN UVLO FB EN OVP CS Ramp LED Current Control Refer Voltage and PWM Dimming LX OVP Ptotection Current Sense (CS) PWM Control and Driver GM & EA Thermal Shutdown GND AN_SY7301A Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY7301A Typical Performance Characteristics (VIN=3.6V, ILED=40mA, 6PCS LED Series(VOUT=18V)) 98%  91%  E ffi ci e n c y E ffi ci e n c y 90%  89%  88%  87%  96%  94%  92%  90%  86%  3 4 5 6 7 8 9 100 111 122 88%  3 4 6 7 8 Quiescent Current vs. Input Voltage LED Current vs. Input Voltage 42 5 150 140 41 130 120 40 110 100 39 90 38 80 4 5 6 7 8 9 10 11 12 Input Voltage (V) AN_SY7301A Rev. 0.9B 3 6 9 12 15 18 21 24 27 30 Input Voltage (V) Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY7301A PWM Dimming （f=400Hz） VEN 2V/div ILED 10mA/d v Time (400μs/div) AN_SY7301A Rev. 0.9B Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY7301A Applications Information SY7301A is a boost regulator IC that integrates the PWM control, power MOSFET on the same die to minimize the switching transition loss and conduction loss. With ultra low RDS(ON) power switches and proprietary PWM control, this regulator IC can achieve the high efficiency and the high switch frequency simultaneously to minimize the external inductor and capacitor size, and thus achieving the minimum solution footprint. 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. COUT FSW ⋅ VOUT ⋅ VRIPPLE VRIPPLE is the peak to peak output ripple voltage. 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. Inductor L: There are several considerations in choo ing this inductor. 1) Sense resistor R1 : Choose R1 to program the proper LED Current. The R1 can be calculated to be: R1 = = IOUT, MAX ⋅ (VOUT − VIN) 0.3 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: L= I LED VIN 2 (VOUT − VIN) VOUT FSW × IOUT, MAX × 40% ILED is the average LED current. Input capacitor CIN: The ripple current through input capacitor is calculated as: I CIN_RMS = VIN ⋅ (VOUT − VIN) 2 3 ⋅ L ⋅ FSW ⋅ VOUT where FSW is the switching frequency and IOUT,MAX is the maximum load current. The SY7301A 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) 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 ins to minimize the potential noise problem. Ca e should be taken to minimize the loop area f rmed by CIN, and IN/GND pins. ISAT, MIN > AN_SY7301A Rev. 0.9B VOUT VIN 3) Output capacitor COUT: The output capacitor is selected to handle the output ripple noise r quirements. 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: The saturation current rating of the inductor must be selected to be greater than the peak inductor current under full load conditions. × IOUT, MAX + VIN 2 VOUT (VOUT − VIN) 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