HT7937 Datasheet | Holtek Semiconductor

Features - Integrated open-circuit protection - Over voltage protection - Up to 84% efficiency at VIN=3V, 3LEDs, - Low standby current: 0.1m A (typ.) (VSHDN=0V) - Matches LED current - Small value inductor and capacitors - Small outline SOT23-6 package ILED= 20m A - 1.2MHz fixed switching frequency Applications - Cellular phones - PDAs - DSCs - Handheld devices - White LED display backlighting General Description The HT7937 is high efficiency boost converter with a constant current output to provide back light functions in handheld devices. Applications with series connected LEDs ensure constant and identical LED currents resulting in uniform brightness. A continuous LED output current is setup using the FB pin regulated voltage across an external sense resistor, RFB connected between the FB pin and ground. The integrated open load protection circuitry prevents damage resulting from an open circuit condition. The low 95m V feedback voltage minimises power losses in the current setting resistor which improves efficiency. The HT7937 has a high switching frequency of up to 1.2MHz which permits the use of lower value extremely small outline inductor and filter capacitor. The HT7937 is supplied in a space-saving, 6-lead SOT23-6 package type. Block Diagram O V P 2 8 V S W .. S H D N F B C o n tro l L o g ic 9 5 m V å 1 .2 M H z O s c illa to r V IN Rev 1.10 January 18, 2010 Pin Assignment S O T 2 3 -6 V IN 6 O V P 5 S H D N 4 T o p V ie w 1 S W 2 G N D 3 F B Pin Description Pin No. 1 2 3 4 5 6 Pin Name SW GND FB SHDN OVP VIN Switching pin Ground pin Output voltage sense node. Connect the cathode of the LED to this pin. A resistor from this pin to ground sets the LED current. Internally pares to 95m V (Typ.). Shutdown device pin. Connect to 1.5V or higher to enable device (ON), 0.3V or lower to disable device (OFF). For over voltage protection connect to the output. Input voltage pin. 2.5V to 5.5V for internal circuitry. Description Absolute...