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ISL97635

SMBus 8-Channel LED Driver

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

• 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

Ordering Information

PART NUMBER

(Note)

PART

MARKING

PACKAGE

(Pb-free)

PKG.

DWG. #

ISL97635IRZ*

976 35IRZ

24 Ld 4x4 QFN

L24.4x4D

*Add “-T” or “-TK” suffix for tape and reel. Please refer to TB347 for

details on reel specifications.

NOTE: These Intersil Pb-free plastic packaged products employ

special Pb-free material sets, molding compounds/die attach

materials, and 100% matte tin plate plus anneal (e3 termination

finish, which is RoHS compliant and compatible with both SnPb and

Pb-free soldering operations). Intersil Pb-free products are MSL

classified at Pb-free peak reflow temperatures that meet or exceed

the Pb-free requirements of IPC/JEDEC J STD-020.

Data Sheet

December 22, 2008