4

Atmel LED Driver-MSL3082

Quick Start Guide

The MSL3082 controls eight strings of series-connected

LEDs at up to at least 500mA per string, and up to

sixteen devices may share the serial interface. The

MSL3082 FET gate drive output is optimized for FETs

requiring no more than 10nC of charge. The MSL3082

PWM engine generates the PWM signal that drives the

strings, or optionally accepts an external PWM signal.

How Many LEDs and Drivers?

The MSL3082 drives eight strings of series-connected

LEDs using external N-channel MOSFETs and current

sense resistors. The LED drive capability (maximum

number of LEDs per string) is limited only by the

MOSFETs and the LED string power supply, not by

SMBus serial interface, with both individual and broadcast

(all MSL3082s on a bus) addressing. The high LED drive

power of the MSL3082 makes it suitable for large LCD

TV and monitor backlights, as well as for LED signage

and general lighting.

LEDs, the String Power Supply, and

the Efficiency Optimizer

The MSL3082 features an Efficiency Optimizer output

that dynamically adjusts the LED string power supply to

the minimum voltage necessary to drive the LED strings,

minimizing power use while assuring accurate LED

current flow. The Efficiency Optimizers features an input

that allows up to eight devices to be connected in a chain

configuration. When implemented, the chain automatically

negotiates, controls, and optimizes the string power

supply for all LED strings driven by the chain.

The power supply can use any topology that employs

external feedback resistors with a maximum feedback

voltage of 1.5V, and are typically DC-DC boost

converters. The efficiency optimizers rely on close

matching of the LEDs connected to a string supply; the

better the matching, the better the overall efficiency.

Differences between Atmel LED

Drivers-MSL3082 and MSL2100

The MSL3082 includes a single Efficiency Optimizer,

is more suited for single-color LEDs, and is ideal for

driving white backlight LEDs in an LCD monitor or TV

application. The MSL2100 includes three independent

Efficiency Optimizer circuits to control three separate

string supplies (for RGB LEDs, for example).

Timing, PWM, Intensity Controls,

and Synchronization

The PWM LED drive signals synchronize to video frame

timing via the PHI input, and to pixel timing via the

GSC input. Suitability for LED backlight architectures is

shown in Table 1 and Table 2. Area LED dimming for

direct backlighting is supported for contrast and color

gamut improvement. With area dimming, motion blur is

reduced by setting each LED string’s PWM phasing to

synchronize string off times with the LCD update timing.

Also, the individual PWM intensity registers for eight

Sixteen drivers (128 LED strings) update in 1.47ms

with a 1MHz bus speed, offering area dimming support

for frame rates up to 640Hz.

BACKLIGHT TYPE

STRING SUPPLY OPTIONS

MOTION BLUR REMOVAL

LED ZONE MANAGEMENT

White LED - bottom edge-lit

1 or more MSL3082 per

efficiency optimized supply

No

No

White LED - top/bottom edge-lit

No

No

White LED - four sides edge-lit

No

No

White LED - direct back-lit

Yes - LED strip phasing

Higher contrast ratio

(area dimming)

RGB LED - direct back-lit

See MSL2100 datasheet

Yes - LED strip phasing

Higher contrast ratio and

color gamut

Table 1. Atmel LED Driver-MSL3082 LED Common Backlight Drive Architectures