ISL97678

8-Channel 45V 50mA LED Driver

OVERVIEW

The ISL97678 is an 8-channel PWM dimming LED driver for LCD backlight applications. The ISL97678 is capable of driving up to 96 pieces of 3.4V/50mA LEDs but larger numbers of LEDs are possible if the LED forward voltage combined is less than 45V. The ISL97678 has 8 channels of voltage controlled current sources with typical currents matching to ±1%, which compensate for the non-uniformity effect of forward voltages variance in the LED strings. To minimize the voltage headroom and power loss in the typical multi-string operation, the ISL97678 features dynamic headroom control that monitors the highest LED forward voltage string and uses its feedback signal for output regulation.

The ISL97678 features PWM dimming up to 30kHz with 0.4%~100% duty cycle and maintains ±1% current matching across all ranges. The PWM dimming frequency can be adjusted between 100Hz and 30kHz. The boost switching frequency can also be adjusted between 600kHz and 1.5MHz.

The ISL97678 features extensive protection functions that include string open and short circuit detections, OVP, and OTP.

The ISL97678 is available in the 32 Ld QFN 5mmx5mm and operates from -40°C to +85°C with input voltage ranges from 4.75V to 26V.

KEY FEATURES

  • 8 channels
  • 4.75V ~ 26V input
  • 45V maximum output
  • Drive typically 96 LEDs (3.4V/50mA each)
  • External PWM input up to 20kHz dimming
  • Dimming range 0.4%~100% up to 30kHz
  • Current matching ±0.7% typical
  • Protections
  • String open circuit and short circuit detections, OVP, and OTP
  • Adjustable dimming frequency
  • Adjustable switching frequency
  • 32 Ld (5mmx5mm) QFN package

BLOCK DIAGRAM

 Block Diagram

PARAMETRICS

Parameters
ISL97678
Basic Information
Production Status
Mass Production
# of Devices/ Channels
8
Total Current for DC/DC Lighting (mA)
400
Output Current Max/Channel (mA)
50
Output Voltage Max (V)
45
Brightness Control
PWM
Input Voltage Max (V)
26
Input Voltage Min (V)
4.75
Backlight for LCD Size (min) (in)
0
Backlight for LCD Size (max) (in)
17
Qualification Level
Standard
Peak Efficiency (%)
93.4
# of LEDs (max)
96
Frequency
1.5 MHz
IS (max)
10 mA
IQ (max)
5 µA
ISW (typ) (mA)
3800
Integrated Diode
No
Over Voltage Protection
Yes
Fault Switch
No
Topologies
Inductor Boost
Input Voltage Range (V)
4.75 to 26
Backlight for LCD Size
up to 17
Can Sample
YES
Temperature Range
-40 to +85

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