HT7938 Datasheet | Holtek Semiconductor

Features - Efficiency up to 85% at VIN=3.6V, 9LEDs, - Tiny inductor and capacitors - Up to 9 strings White-LED - Tiny 6-lead SOT23-6 package - Built in OVP, OCP, OTP, UVLO protection ILED=20m A - 1.2MHz fixed switching frequency - Low Standby Current: 0.1m A, VEN=0V (typ.) - Matches LED current Applications - Cellular phones - PDAs - DSCs - GPS - Handheld devices - White LED display backlighting General Description HT7938 is high efficiency boost converter with constant current output to provide backlight in handheld devices. Series connection of LEDs provides constant identical LED currents resulting in uniform brightness. The continuous LED current is set with FB pin regulated voltage across an external sense resistor (RFB) connected from that pin to ground. The built-in open load protection prevents the damage resulting from an open circuit condition. Low 200m V feedback voltage minimizes power loss in the current setting resistor for better efficiency. HT7938 switches at rates up to 1.2MHz to allow the use of extremely small inductor and filter capacitor. Block Diagram 36V .. Rev 1.00 November 11, 2009 Pin Assignment V IN 6 O V P 5 E N 4 T o p V ie w H T 7 9 3 8 S O T 2 3 -6 -A 1 S W 2 G N D 3 F B Pin Description Pin Name EN GND I/O I ¾ Description Shutdown & Dimming control input. Don¢t allow this pin to float. Signal Ground. Feedback pin. Reference voltage. The HT7938 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 Switching pin. Internal power MOSFET drain. Connected to inductor and diode. Input supply pin. The input supply pin for the IC. Connect VIN to a supply voltage between 2.6V~5.5V. Over voltage protection pin which is connected to the output. SW VIN OVP Absolute Maximum Ratings Input Voltage 6.0V FB Voltage...