MSL3085 datasheet(4/20 Pages) ATMEL

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Atmel LED Driver-MSL3085

Atmel LED Driver

MSL3085 Overview

The MSL3085 controls eight strings of series-connected

LEDs at up to 350mA per string. Eight MSL3085s can

share a serial interface. The MSL3085 FET gate drive

output is optimized for FETs requiring no more than

10nC of charge. The MSL3085 PWM engine generates

the PWM signal that drives the strings, or optionally

accepts an external PWM signal.

LED Power Supplies and Efficiency Optimizers

The MSL3085 features two efficiency optimizer outputs

that dynamically adjust the LED string power supplies

to their minimum voltage necessary to drive the LED

strings, while assuring accurate LED current flow. One of

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 supplies can use any topology, 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.

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. Area LED dimming 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. The MSL3085 also includes internal

PWM timing generation for standalone (non-video)

LED lighting applications. Table 1 presents the available

methods of LED intensity control.

Table 1. LED Intensity Controls

LED INTENSITY CONTROL

EFFECT

RESOLUTION

Global LED string current

adjust

Reduces string current globally

from maximum set by FET

source resistors

ISTR (0x31)

8 bits

Global LED string PWM

Global PWM scaling

GINT (0x2F)

and ALTGINT (0x30)

8 bits

Individual LED string PWM

PWM individual string control

PWMn (0x60 thru 0x7D)

and

ALTPWMn (0xA0 thru 0xBD)

12 bits

External resistor from FET

source to ground

Sets maximum individual

string current

External PWM input

Optionally controls all string

PWM drives

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