HT7938
High Current and Performance White LED Driver
Features
·
Efficiency up to 85% at V
IN
=3.6V, 9LEDs,
·
Tiny inductor and capacitors
·
Up to 10 strings White-LED (LED V
F(Max.)
=3.5V)
·
Tiny 6-lead SOT23-6 package
·
Built in OVP, OCP, OTP, UVLO protection
I
LED
=20mA
·
1.2MHz fixed switching frequency
·
Low Standby Current: 0.1mA, V
EN
=0V (typ.)
·
Matches LED current
Applications
·
Cellular phones
·
PDAs
·
DSCs
·
GPS
·
Handheld devices
·
White LED display backlighting
General Description
HT7938 is high efficiency boost converter with constant
current output to provide backlight in handheld devices.
Series connection of LEDs provides constant identical
LED currents resulting in uniform brightness. The con-
tinuous LED current is set with FB pin regulated voltage
across an external sense resistor (R
FB
) connected from
that pin to ground. The built-in open load protection pre-
vents the damage resulting from an open circuit condi-
tion. Low 200mV feedback voltage minimizes power
loss in the current setting resistor for better efficiency.
HT7938 switches at rates up to 1.2MHz to allow the use
of extremely small inductor and filter capacitor.
Block Diagram
Rev 1.10
1
March 19, 2010
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
