The ISL97635 is a digitally controlled LED driver that
controls 8 channels of LED current for LCD backlight
applications. The ISL97635 is capable of driving typically 72
(8x9) pieces of 3.5V/30mA or 80 (8x10) pieces of
3.2V/20mA LEDs. The ISL97635’s 8 channels of voltage
controlled current sources with typical currents matching of
±1%, which compensate for the non-uniformity effect of
forward voltages variance in the LED stacks. To minimize the
voltage headroom and power loss in the typical multi-strings
operation, the ISL97635 features a dynamic headroom
control that monitors the highest LED forward voltage string
and uses its feedback signal for output regulation.
The LED dimming control can be achieved through a
SMBus, an external PWM, or a variable DC (analog light
sensor) input. SMBus controlled dimming allows 256 levels
each of PWM and DC current adjustments. The SMBus
PWM dimming frequency can be adjusted from 100Hz to
5kHz by an external capacitor. External PWM input allows up
to 20kHz audio noise free PWM dimming. The SMBus PWM
setting and an external PWMI signal can also be combined
to provide a dynamic PWM dimming that complies with
Intel’s DPST (Display Power Saving Technology)
requirement.
One or more channels can be selected sequentially in any
order, allowing scrolling in RGB LED backlighting
applications.
The ISL97635 features extensive protection functions that
include string open and short circuit detections, OVP, OTP,
thermal shutdown and an optional input overcurrent
protection with master fault disconnect switch. The fault
conditions will be recorded in the Fault/Status register. There
are selectable short-circuit thresholds and the switching
frequency can be programmed between 600kHz and
1.2MHz.
Available in the 24 Ld 4mmx4mm QFN, the ISL97635
operates from -40°C to +85°C with input voltage ranging
from 6V to 24V.

Features
• 8 Channels
• 6V to 24V Input
• 34.5V Output Max
• Drive Maximally 72 (3.5V/30mA each) or 80 (3.2V/20mA
each) LEDs
• Current Matching ±1% Typ
• Dynamic Headroom Control
• Dimming Controls
- SMBus 8-Bit PWM Current Control
- SMBus 8-Bit DC Current Control
- External PWM Input up to 20kHz Dimming
- SMBus and External PWM DPST Dimming Control
- DC-to-PWM Dimming Control
• Protections
- String Open Circuit Detection
- String Short Circuit Detection with Selectable Thresholds
- Over-Temperature Protection
- Overvoltage Protection
- Input Overcurrent Protection with Disconnect Switch
• 600kHz/1.2MHz Selectable fSW
• Selectable Channels Allows Scrolling Backlight
• 24 Ld (4mmx4mm) QFN Package
• Pb-Free (RoHS compliant)

Applications
• Notebook Displays WLED or RGB LED Backlighting
• LCD Monitor LED Backlighting
• Automotive Displays LED Backlighting
• Automotive or Traffic Lighting