HT7939 Datasheet | Holtek Semiconductor

Features - Input range from 2.6V~5.5V - Built-in Power MOSFET - Can drive up to 39 White LEDs with a 5V input - Low standby current: 0.1m A (typ.) with VEN low - Integrated Over-voltage, Over-temperature and - Under voltage lock-out protection - 1.2MHz fixed switching frequency - High efficiency - up to 90% - 6-pin SOT23-6 package Over-current protection circuits Applications - Display Backlighting - LED lighting Automatic DVD player Digital photo frame Handheld puter General Description The HT7939 is a high efficiency boost converter for driving White LEDs using current mode operation. The device is designed to drive up to 39 White LEDs from a 5V power supply. The White LED current is setup using an external current setting resistor, which has a low feedback voltage of 0.2V to minimise power losses in the resistor which improves efficiency. The Over-voltage function prevents damage to the IC by turning off the converter when the LED load is open circuit. The device includes over current protection, over temperature protection and under voltage protection preventing damage to the device when the output is overloaded. .. Rev 1.10 November 3, 2009 Block Diagram 32V Pin Assignment S O T 2 3 -6 V IN 6 O V P 5 E N 4 T o p V ie w 1 S W 2 G N D 3 F B Pin Description Pin No. .. 1 2 Pin Name SW GND Description Switching pin. Internal power MOSFET drain. Connected to inductor and diode. Signal Ground. Feedback pin. Reference voltage. The HT7939 feedback voltage is 200m V. Connect the sense resistor from FB to GND to set the LED current. Calculate resistor value according to 200m V . RFB = ILED Shutdown & Dimming control input. Don¢t allow this pin to float. Over voltage protection pin which is connected to the output. Input supply pin. The input supply pin for the IC. Connect VIN to a supply voltage between 2.6V~5.5V. 4 5 6 EN OVP VIN Rev 1.10 November 3, 2009 Absolute Maximum...