ISL97678_14 Datasheet, PDF (1/16 Pages) Intersil Corporation – 8-Channel 45V, 50mA LED Driver

8-Channel 45V, 50mA LED Driver
ISL97678
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 is 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.
ISL97678 is available in the 32 Leads QFN 5mmx5mm and
operate from -40°C to +85°C with input voltage ranges from
4.75V to 26V.
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
Applications
• Notebook Displays WLED or RGB LED Backlighting
• LCD Monitor LED Backlighting
V_IN
4.75V~26V
CIN
10µF
PROCESSOR
R_SET
R_FPWM
RFSW
VIN
EN
PWM
10µH/3A
3x4.7µF/50V
LX
OVP
45V*, 50mA per String
96 (8x12) LEDs
C_OUT
ISL97678
RSET
FPWM
FSW
AGND
PGND
CH1
CH2
CH8
LED
BACKLIGHT
FIGURE 1. TYPICAL APPLICATION CIRCUIT: TFT-LCD NOTEBOOK DISPLAY
May 6, 2014
FN6998.2
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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