ISL97687

4-Channel LED Driver with Phase Shift Control and 10-Bit Dimming Resolution

Product Status: Mass Production

OVERVIEW

The ISL97687 is a PWM controlled LED driver that supports four 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 VOUT necessary for regulation. This adaptive scheme 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 that 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.

KEY 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
        • VSYNC function to synchronize PWM signal to frame rate
        • 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

BLOCK DIAGRAM

 Block Diagram

PARAMETRICS

Parameters
ISL97687
Basic Information
Production Status
Mass Production
# of Devices/ Channels
4
Total Current for DC/DC Lighting (mA)
700
Output Current Max/Channel (mA)
160
Output Voltage Max (V)
75
Brightness Control
PWM or LED DC current control
Input Voltage Max (V)
32
Input Voltage Min (V)
9
Backlight for LCD Size (min) (in)
0
Backlight for LCD Size (max) (in)
29
Qualification Level
Standard
Peak Efficiency (%)
90
# of LEDs (max)
4-Channel 75V 160mA LED Driver
Frequency
0.2, 0.6, 1.2 MHz
IS (max)
5.5 mA
IQ (max)
5 µA
ISW (typ) (mA)
3400
Integrated Diode
Yes
Over Voltage Protection
Yes
Fault Switch
Yes
Topologies
Inductor Boost
Input Voltage Range (V)
9 to 32
Backlight for LCD Size
up to 29
Can Sample
YES
Temperature Range
-40 to +105

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