1

4-Channel LED Driver with Phase Shift Control and

10-Bit Dimming Resolution

ISL97687

The ISL97687 is a PWM controlled LED driver that supports

4 channels of LED current, for Monitor and TV LCD backlight

applications. It is capable of driving 160mA per channel from a

9V to 32V input supply, with current sources rated up to 75V

absolute maximum.

The ISL97687’s current sources achieve typical current matching

to ±1%, while dynamically maintaining the minimum required

compensates for the non-uniformity of forward voltage variance

in the LED strings.

The ISL97687 can decode both an incoming PWM signal and an

analog input voltage, for DC-to-PWM dimming applications.

Modes include direct PWM and several modes where the PWM

frequency is synthesized on chip at 10-bit resolution. This can be

either free running, or synchronized with the frame rate to give

both a frequency and a phase lock, minimizing panel to panel

variation and display flicker. Phase shift is supported, reducing

flicker and audio noise, as is multiplication of the incoming

decoded analog and PWM values.

The ISL97687 has an advanced dynamic headroom control

function, which monitors the highest LED forward voltage string,

and regulates the output to the correct level to minimize power

loss. This proprietary regulation scheme also allows for

extremely linear PWM dimming from 0.02% to 100%. The LED

current can also be switched between two current levels, giving

support for 3D applications. The ISL97687 incorporates

extensive protections of string open and short circuit detections,

OVP, and OTP.

Features

• 4x160mA, 75V rated channels with integrated channel

regulation FETs

• Channels can be ganged for high current

-2x350mA

-1x700mA

• 9V~32V input voltage

•Dimming modes:

- Direct PWM dimming from 100Hz~30kHz

- PWM dimming with adjustable output frequency

- 10-bit dimming resolution

- Phase shift

- Analog to PWM dimming with 8-bit resolution

• 2 selectable current levels for 3D applications

•Current matching of ±1%

• Integrated fault protection features such as string open circuit

protection, string short circuit protection, overvoltage

protection, and over-temperature protection

• 28 Ld 5mmx5mm TQFN and 28 Ld 300mil SOIC Packages

Available

Applications

• Monitor/TV LED Backlighting

• General/Industrial/Automotive Lighting

Related Literature

• See AN1674 for “ISL97687IRTZ-HEVALZ and ISL97687IRTZ-

LEVALZ Evaluation Board User Guide” for TQFN Application

• See AN1706 for “ISL97687IBZ-EVAL1Z Evaluation Board User

Guide” for SOIC Application

FIGURE 1. ISL97687 APPLICATION DIAGRAM

FIGURE 2. PWM DIMMING LINEARITY

PWMI

EN_ADIM

OSC

GD

PWM_SET/PLL

EN

OVP

VIN

STV

VLOGIC

VDC

EN_VSYNC

D1

CS

CH1

CH2

CH3

CH4

CSEL

ISET2

EN_PS

COMP

FUSE

ACTL

PGND

SLEW

VIN: 9V~32V

160mA MAX PER STRING

Q1

ISET1

0

10

20

30

40

50

60

70

80

90

100

110

0

20

40

60

80

100

DIMMING DUTY CYCLE (%)

I_CH2

I_CH1

I_CH3

I_CH4

September 27, 2012

FN7714.1

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

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