DN79 - Zetex Semiconductors

DN79 ZXSC400 1W LED driver

ZXSC400 is configured to the reference design below. The target application is a 1W white LED driven from a two cell NiCd/NiMH or alkaline battery input for flashlights and high powered LED driving. The supply voltage for ZXSC400 reference design is: VIN = 1.8V ~ 3V. L1 22uH VIN D1 ZHCS1000 C1 100uF/6V3 U1 ZXSC400 VCC VDRIVE STDN ISENSE GND VFB Q1.

Features

olerance C1 100␮F/6V3 1812 18126D107KAT2A AVX www.avx.com 100␮F/6V3/X5R/1812 C2 100␮F/6V3 1812 18126D107KAT2A AVX www.avx.com 100␮F/6V3/X5R/1812 LED1 1W N/A LXHL-PW01 Lumileds www.lumileds.com 1W white LED emitter Table 1 Bill of materials Issue 1 - May 2005 © Zetex Semiconductors plc 2005 1 www.zetex.com DN79 Performance Increasing efficiency On ZXSC400 reference design, R1 is set to 22mΩ to ensure that the LED current is regulated over the full input voltage range of 3V ~ 1.8V. For improved efficiency R1 can be changed to a 33mΩ resistor but LED current will not be regulated belo.