HT7938A_13 Datasheet, PDF (1/13 Pages) Holtek Semiconductor Inc – High Current and 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 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-3 (V_FB=300mV)
Rev. 1.10
1
February 01, 2013