Datasheet

22
Atmel MSL3086/MSL3088 Datasheet
8-String 60mA LED Drivers with Integrated Boost Controller and Phase Shifted Dimming
10.0 LED Dimming Control
10.1 External and I
2
C Control of LED Brightness
Control MSL3086 LED brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PWM input. The
PWM dimming signals (outputs) take the frequency and duty cycle of the input signal but are staggered in time so that they start at
evenly spaced intervals relative to the PWM input signal. When one or more strings are disabled by fault response, the stagger delays
automatically re-calculate for the remaining enabled strings.
The MSL3088 accepts two input signals, SYNC and PWM. SYNC provides the frequency information for the PWM dimming, and PWM
provides the duty cycle information. The LED PWM dimming signals are staggered based on the frequency at SYNC.
For all devices, use PWM and SYNC inputs frequency between 20Hz and 50kHz and duty cycle between 0% and 100% (avoid duty
cycles above 99.97% and less than 100%).
Additionally, internal registers accessed using the I2C compatible serial interface allow control of the PWM dimming frequency and duty
cycle. For programming details see the MSL3040/50/60/80/86/87/88/89 Programming Guide.
10.2 Phase Shifted LED Dimming Signals
By default, string PWM dimming is staggered in time to reduce the transient current demand on the boost regulator. The MSL3086/88
automatically determine the stagger times based on the number of enabled strings and the PWM dimming frequency.