HT7938A Datasheet, PDF (1/13 Pages) Holtek Semiconductor Inc – Performance White LED Driver

HT7938A
High Current and
Performance White LED Driver
Feature
• Efficiency up to 90% at V_IN=4.0V, 5S2P,
I_LED=20mA
• 1.2MHz fixed switching frequency
• Low standby current: 0.1mA (typ.) at V_EN=0V
• Matches LED current
• Tiny inductor and capacitors
• EN pin dimming frequency up to 200kHz
• 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
Applications
• Cellular phones
• PDAs
• DSCs
• Handheld devices
• White LED display backlighting
General Description
The HT7938A is high efficiency boost converter with
constant current output for backlight applications in
handheld devices. Using a series connection of LEDs
provides constant identical LED currents resulting in
uniform brightness. The continuous LED current is
set using the device FB pin regulated voltage across
an external sense resistor, R_FB, connected between this
pin and ground. The integrated open load protection
feature prevents device damage resulting from
open circuit load conditions. A low 200mV/300mV
feedback voltage minimises power losses in the
current setting resistor which provides enhanced
efficiency. The HT7938A has a dimming frequency of
up to 200kHz, which has excellent linear performance
over this dimming frequency range. The device
switches at rates of up to 1.2MHz to allow the use of
extremely small inductors and filter capacitors.
Selection Guide
Part No.
HT7938A
Package
SOT23-6
Note: Both lead free and green compound devices are available.
Marking
38A-2 (V_FB=200mV)
38A-3 (V_FB=300mV)
Rev. 1.00
1
April 19, 2012