LP85571 datasheet(18/49 Pages) TI2

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Brightness (PWM)

Time

Slope Time

Advanced slope

Brightness (PWM)

Sloper Input

PWM Output

Time

Normal slope

LED1

LED2

LED3

LED4

LED5

LED6

60 degrees

Phase Delay

1/(fPWM)

Cycle Time

LP8557, LP85571

SNVSA15B – DECEMBER 2013 – REVISED DECEMBER 2015

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Feature Description (continued)

Figure 30. Phase Shift PWM Dimming Scheme Diagram

8.3.3 Slope and Advanced Slope

The transition time between two brightness values can be programmed with the STEP bits from 0 to 200 ms. The

same slope time is used for sloping up and down. With advanced slope the brightness changes can be made

more pleasing to a human eye. It is implemented with a digital smoothing filter. The filter strength is set with

SMOOTH bits.

Figure 31. Slope and Advanced Slope

8.3.4 LED String Count Auto Detection

The LP8557 and LP8557I can auto-detect the number of the LED strings attached. During the auto-detect

routine, the devices automatically remove the unused current sink(s) and adjust the phasing of the remaining

current sinks. The LED OPEN* fault condition is not supported with auto-detect function enabled. On the

LP8557I, the user may disable the function by setting CONFIG.AUTO bit to 0 via an I2C write.

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LP85571 Datasheet(PDF) 18 Page - Texas Instruments