CAT32TDI-GT3 ON Semiconductor

CAT32 CMOS White LED Driver Description The CAT32 is a DC/DC step up converter that delivers a regulated output current. Operation at a constant switching frequency of 1.2 MHz allows the device to be used with very small value external inductor and ceramic capacitors. CAT32 Typical Application Circuit D1 L 6.8 H 1 VIN C1: Taiyo Yuden JMK212BJ475 2.7 V C2: Taiyo Yuden EMK212BJ105 to D1: Zetez ZHCS400 4.2 V C1 L1: Sumida CLQ4D106R8 4.7 F 1 (Panasonic ELJEA6R8) 6 SW VIN CAT32 PWM 3 5 C2 DIMMING SHDN LED 1 F CONTROL RSET GND 15 mA 4 2 R SET 1.50 k TSOT23 Pin Numbers Figure 1. LiIon Driver for Four HighBrightness White LEDs Table 1. PIN DESCRIPTION Pin Number Pin Number SOT23 TDFN Name Function 1 8 SW Switch pin. This is the drain of the internal power switch. For minimum EMI, min- imize the trace area connected to this pin. 2 5 GND Ground pin. Connect pin 2 to ground. 3 6 LED LED (cathode) connection pin. 4 4 RSET RESET pin. A resistor connected from pin 4 to ground sets the LED current. This pin is also used to dim the LEDs. 5 3 SHDN Shutdown pin. 6 2 VIN Input supply pin. This pin should be bypassed with a capacitor to ground. A 4.7 F capacitor mounted close to the pin is recommended. 1 Power Power Ground Ground