SGM3123 Datasheet, PDF (7/10 Pages) SG Micro Corp – White LED Driver with LowDropout CurrentSource

SGM3123
TYPICAL APPLICATION
White LED Driver with
Low Dropout Current Source
+
_
1µF
PWM
VIN
VOUT
SGM3123
PGND
LED1
LED2
EN
LED3
EN
LED4
GND
Figure 1. Application Circuit for Backlight
APPLICATION INFORMATION
Enable Input
Drive EN high to enable the device; drive EN low to force
LED1, LED2, LED3 and LED4 into a high-impedance
state. When driven high, EN draws190μA 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
An input capacitor at the V_CC pin could reduce ripple
voltage. It is recommended to use a ceramic 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 SGM3123 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.
SG Micro Corp
7
www.sg-micro.com