3-Channel Low Dropout

Low Side White LED Driver

7

SG Micro Corp

www.sg-micro.com

SGM3128

APPLICATION INFORMATION

Enable Input

Drive EN high to enable the device; drive EN low to force

LED1, LED2 and LED3 into a high-impedance state.

When driven high, EN draws 240μA to power the IC.

Driving EN low longer than 3ms will disable the device

and the typical supply current will be less than 1µA.

Input UVLO

The input operating voltage range of the SGM3128 is

reduce ripple voltage. It is recommended to use a

ceramic 0.1μF or larger capacitance as the input

capacitor. This IC provides an under voltage lockout

(UVLO) function to prevent it from unstable issue when

startup. The UVLO threshold of input rising voltage is set

at 2.1V typically with a hysteresis 0.11V.

LED Brightness Dimming Control

For controlling the LED brightness, the SGM3128 can

perform the dimming control by applying a PWM signal to

EN pin. When an external PWM signal is applied to the

EN pin, brightness of white LED is adjusted by the duty

cycle. The average LED current is proportional to the

PWM signal duty cycle. The magnitude of the PWM

signal must be higher than the minimum level of enable

input high level, in order to let the dimming control

perform correctly. The suggested PWM frequency range

is 20kHz to 200Hz.