EN pin dimming:
serial pulse train input
V
EN
I
OUT
PWM pin dimming:
digital PWM input
I
OUT
V
PWM
I
OUT
V
APWM
APWM pin dimming:
analog PWM input
FSET
COMP
ISET
RISET
RFSET
APWM
LED1
LED3 LED5 LED7 LGND
SKIP
C
C
VIN SW SW OVP
COUT
V
IN
ROVP
D1
V
IN
5 V ±10%
V
BAT
5 to 25 V
C
BAT
1 μF/ 25 V
C
IN
0.1 μF/ 10 V
2.2 μF
50 V
L1
10 μH
A8500
LED8 LED6 LED4
LED2
SEL1
SEL2
SEL3
EN
PWM
AGND
PGND
Approximate Scale 1:1
Typical Application
Description
The A8500 is a multi-output WLED driver for medium display
backlighting. The A8500 integrates a boost converter and eight
current-sinks to provide a flexible WLED/RGB backlight
driver. The boost converter can provide output voltage up to
47 V. The flexible channel selection control and high voltage
capability allow a wide range of LED backlight applications.
The A8500 can support any application requiring 4 to 96
WLEDs. The boost converter is a constant frequency current-
mode converter.
Each LED channel can sink 25 mA, and channels can be
paralleled for higher currents. Flexible dimming allows output
channels to either run at an adjustable DC value or with
externally controlled PWM duty cycles.
The A8500 is available in a 26 pin, 4 mm × 4 mm QFN/MLP
package that is only 0.75 mm nominal in height. Applications
include:
▪ Thin notebook displays
▪ LCD TV
▪ RGB backlight
▪ GPS systems
▪ Portable DVD players
8500P-DS
Features and Benefits
▪ Active current sharing between LED strings for ±1.5%
typical current matching and ±1.2% typical accuracy
▪ Drive up to 12 series × 8 parallel = 96 LEDs
(V
f
= 3.2 V, I
f
= 20 mA)
▪ Flexible dimming, using alternative methods:
▫ LED duty cycle control (PWM pin)
▫ DC current using serial programming (EN pin)
▫ DC current using external PWM signal (APWM pin)
▫ An external resistor
▪ Boost converter with integrated 50 V, 2 A DMOS
▪ LED sinks rated for 25 mA
▪ 200 kHz to 2 MHz switching frequency
▪ Open LED disconnect
▪ Boost current limit, thermal shutdown, and soft start
▪ No audible ceramic capacitor noise during PWM dimming
▪ Adjustable overvoltage protection (OVP)
▪ No pull-up resistors required for LED modules that use
ESD capacitors
Flexible WLED/RGB Backlight Driver for Medium Size LCDs
Package: 26 pin QFN/MLP (suffix EC)
A8500
Figure 1. LCD monitor backlight, driving 96 LEDs. LED V
f
= 3.2 V, 20 mA per LED string. Overvoltage
protection set to 45 V nominal (40.5 V minimum). Alternative dimming control pulse trains illustrated
for EN, PWM, and APWM control. See also: Recommended Components table, page 14.
