HT7945 Datasheet, PDF (1/11 Pages) Holtek Semiconductor Inc – White LED Backlight Driver

HT7945
White LED Backlight Driver
Features
• Max input voltage: 26V
• Integrated Power Mosfet
• Output voltage up to 40V driving 11 series
LEDs – LED Vf(max)=3.5V per string – absolute
max rating up to 44V
• Channel Phase Shift PWM Dimming
• Drives up to 12 LED strings under Vf(max.)=3.3V
condition
• Low string feedback voltage: 0.8V at 20mALED
current
• Switching frequency: 500kHz/1MHz
• 8-string constant current output
• LED current adjustable from 15mA to 30mA
• ±1.5% current matching between strings
• PWM dimming control
• 1% minimum dimming duty-cycle at 2kHz
• Integrated soft start function
• LED failure detection: open and short circuit
• Capacitor type: ceramic
• Protection: OVP, OTP, UVLO, SW current limit
• Small 24-pin outline package: 4mm×4mm,
thin QFN type
Applications
• LED backlights for notebook and tablet PC
General Description
The HT7945 is a high efficiency DC-DC controller
which can drive multiple WLEDs connected in a
series/parallel configuration. The device has a wide
input voltage, ranging from 4.5V to 26V, and an
adjustable 15mA to 30mA WLED current, setup using
an external resistor. In total, the device can support up
to 88 WLED.
In addition, eight current sink regulators provide
±1.5% high precision current matching between
strings. The brightness can be adjusted by an external
PWM signal with frequency up to 20kHz. Once an
open/short string is detected, that string is disabled
while the other strings continue to operate normally.
Other protection includes soft-start, under voltage
lockout, programmable over voltage protection,
switch current limit and thermal shutdown.
The HT7945 is supplied in a QFN 24 pin 4x4 tiny
footprint package type
Rev. 1.00
1
April 13, 2012