SY7200AABC

Application Note: AN_SY7200A 30V High Current Boost LED Driver Preliminary Specification General Description Features SY7200A is DC/DC step-up converter that deliver an accurate constant current for driving LEDs. Operation 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 SY7200A 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 2A Drives LED strings up to 30V 1MHz fixed frequency minimizes the external components Dimming frequency for EN/PWM pin: 20kHz~1MHz Internal softstart limits the inrush current Open LED over voltage protection RoHS Compliant and Halogen Free SY7200 □(□□)□ Temperature Code Package Code Optional Spec Code Applications • • • Temperature Range: -40°C to 85°C Ordering Number SY7200AABC Package type SOT23-6 Dimming 20kHz~1MHz GPS Navigation Systems Handheld Devices Portable Media Players Typical Applications L D Vin Vout Cin IN Dimming EN/PWM GND Cout LX OVP FB R1 Figure 1. Schematic Diagram AN_SY7200A Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY7200A Pinout (top view) (SOT23-6) Top mark: HYxyz (Device code: HY, x=year code, y=week code, z= lot number code) Pin Name LX GND Pin Number 1 2 FB 3 EN/PWM 4 OVP IN 5 6 Pin Description Inductor node. Connect an inductor between IN pin and LX pin. Ground pin. Feedback pin. Connect a resistor R1 between FB and GND to program the output current: IOUT=0.2V/R1. Enable and dimming control. When used as enable input, pull high to turn on IC. When used as dimming input, the first pulse should be longer than 200ns to turn on IC. And the ecommend dimming frequency range is 20kHz~1MHz. Over voltage protection. The typical value is 30V. Input pin. Decouple this pin to GND pin with ceramic capacitor. Absolute Maximum Ratings (Note 1) IN, EN ---------------------------------------------------------- ---------------------------------------------------- 32V 36V 4V All other pins --------------------------------------------------------------------------------------------------------0.6/0.55W Power Dissipation, PD @ TA = 25°C, SOT23-6 ------------------------------------------------------Package Thermal Resistance (Note 2) 170/180°C/W θJA ----------------------------------------------------------------------------------------------125°C Junction Temperature Range ----------------------------------------------------------------------------------260°C Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------65°C to 150°C Storage Temperature Range ------------------------------------------------------------------------LX, OVP ----------------------------------------------------------------------------------------------------------- Recommended Operating Conditions (Note 3) Input Voltage Supply-------------------------------------------------------------------------------------2.8V to 30V Junction Temperature Range ------------------------------------------------------------------------ - 40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------- -40°C to 85°C AN_SY7200A Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY7200A 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 Input UVLO Threshold UVLO Hysteresis Oscillator Frequency Min On Time Max Duty Cycle Thermal Shutdown Thermal Hysteresis Output Clamp voltage PWM dimming frequency Symbol V IN I Q I SHDN V REF I FB R DS(ON) I LIM V ENH V ENL V UVLO V HYS F OSC T SD T HYST V OCL Conditions Min 2.8 VFB=0.3V EN=0 196 Typ 0.1 10 200 VFB=0.3V Max 30 0.6 15 204 1 220 2 1.5 0.4 2.7 0.1 1.0 100 90 150 20 30 IOUT=100mA “Open LED” 20k 1M Unit V mA uA mV uA mΩ A V V V V MHz ns % ℃ ℃ V Hz Note 1: Stresses beyond the “Absolute Maximum Ra ings” 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: θJA is measured in the natural co vection 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. AN_SY7200A Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY7200A Typical Performance Characteristics (VIN=5V, ILED=0.3A, 5PCS LED Series) Efficiency vs. Input Voltage 96 LED Current (mA) 94 92 90 88 86 ILED=0.3A 84 4 5 6 7 8 9 10 11 12 Input Voltage (V) Quiescent Current vs. Input Voltage 150 140 130 120 110 100 90 80 3 6 9 12 15 18 21 24 27 30 Input Voltage (V) AN_SY7200A Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY7200A Shutdown from VIN VLX 10V/div VIN 2V/div I LED 0.2A/div Time (2ms/div) AN_SY7200A Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY7200A Applications Information 1) Because of the high integration in the SY7200A IC, the application circuit based on this regulator IC is rather 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: R1 =I 0.2 LED 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= VIN 2 (VOUT − VIN) VOUT FSW × IOUT, MAX × 40% where FSW is the switching frequency and IOUT,MAX is the maximum load current. The SY7200A 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. ILED is the average LED current. 2) Input capacitor CIN: The ripple current through input capacitor is calculated as: I CIN_RMS = VIN ⋅ (VOUT − VIN) ISAT, MIN > 2 3 ⋅ L ⋅ FSW ⋅ VOUT A typical X7R or better grade ceramic capacitor with larger than 4.7uF capacitance can handle this ripple current well. To minimize the potential noise problem, place this 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. Output capacitor COUT: The output capacitor is selected to handle the output ripple noise requirements. This ripple voltage s related to the capacitor’s capacitance and its equivalent series resistance (ESR). For the best performance, it is recommended to use X7R or better grade low ESR ceramic capacitor. The voltage rating of the output capacitor should be higher than the maximum output voltage. The minimum requi ed 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. Inductor L: There are several considerations in choosing this inductor. AN_SY7200A Rev. 0.1 The saturation current rating of the inductor must be selected to be g eater than the peak inductor current under full l ad conditions. VOUT VIN 3) × IOUT, MAX + VIN 2 (VOUT − VIN) VOUT 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