MSLB9082 datasheet(13/20 Pages) ATMEL

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Atmel LED Driver-MSLB9082

Setting the Internal PWM Dimming

Frequency and Duty Cycle

The MSL3162 internally generates the PWM dimming

duty cycle and frequency. The PWM dimming

frequency is programmable, as are the PWM duty cycle

and phasing between LED strings.

Setting the PWM Dimming Frequency

The PWM frequency (PHI frequency) is internally set

by the IPHIGEN register. This 16-bit number sets the

divider ratio from an internal 2.5MHz clock. Therefore,

the PWM frequency is:

IPHIGEN

MHz

PWM

For high dimming accuracy, keep the PWM dimming

frequency below 10kHz. To set the PWM frequency,

program the IPHIGEN register between 38Hz and

10kHz per the equation:

PWM

MHz

IPHIGEN

where IPHIGEN ranges between 250 (0x00FA) and

65535 (0xFFFF)

For full PWM dimming resolution, make sure that the

ratio between the IGSCGEN register and IPHIGEN

Resolution for more details.

Setting the PWM Dimming Resolution

The MSL3162 uses the IPHIGEN register to set the

PWM dimming frequency, and it uses the IGSCGEN

frequency). The MSL3162 internally counts using the

frequency set by the IGSCGEN register to set the PWM

duty and phasing. Full PWM dimming is achieved if the

ratio of IGSCGEN to IPHIGEN is less than 32. If the ratio

is greater than 32, then the maximum achievable duty

cycle is:













−

IPHIGEN

IGSCGEN

MAX

For D

MAX>1, the maximum duty cycle is 100%.

Setting the LED PWM Dimming Duty Cycle

The MSL3162 allows each LED string to operate at

different duty cycles and phases. The per-string PWM

dimming duty cycle for any LED string is set by the

PWMn register, where n is the LED string number.

The MSL3162 also offers PWM dimming of all strings

simultaneously through the global intensity (GINT)

most-significant bits of the product of the PWMn

and GINT registers, multiplied by the GSC period:

























−





















GINT

PWMn

MHz

IGSCGEN

GINT

PWMn

GSC

ON_PWMn

tON_PWMn

where PWMn ranges from 0 to 256 (0xFF) and GINT

ranges from 0 to 64 (0x3F).

Setting the LED PWM Dimming Phasing

Each LED string’s PWM dimming occurs with

independent phasing. This is useful to force phase

shifted PWM dimming, which reduces the transient load

on the DC-DC converter, improving performance.

The phase of each LED string is set by PHDLYn,

where n is the LED string number. The MSL3162

counts GSC pulses to determine the on-time delay

from the beginning of each PHI frame. For example,

if PHDLY0 is set to 0x00, the LED string 0 on time

starts at the beginning of a PHI frame. If PHDLY0 is

set to 0x40, the LED string 0 on time begins at 64

(0x40) GSC pulses after the beginning of a PHI frame.

PHDLYn

MHz

IGSCGEN

PHDLYn

GSC

PHDLYn













−









Atmel LED Driver-MSLB9082

LED Backlight Driver Module

Compact, 8-channel, 20W LED Driver Board with I2C Interface

MSLB9082 Datasheet(PDF) 13 Page - ATMEL Corporation

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