+1 LSB

PWM value 510 (10-bit)

PWM value 510 1/2 (10-bit)

PWM value 511 (10-bit)

Brightness (PWM)

Time

Slope Time

Advanced slope

Brightness (PWM)

Sloper Input

PWM Output

Time

Normal slope

Steady state without dithering

If dither is enabled it will

be used during transition

to enable smooth effect

OUT1

OUT2

OUT3

OUT4

tSHIFT = 1/(FPWM x 4)

Shift time

1/(FPWM)

Cycle time

LP8553

www.ti.com

SNVS701B – SEPTEMBER 2011 – REVISED JANUARY 2014

Figure 17. Phase Shift PWM Mode

Slope and Dithering

During transition between two brightness (PWM) values special dithering scheme is used if the slope is enabled.

It allows increased resolution and smaller average steps size. Dithering is not used in steady state condition.

Slope time can be programmed with EEPROM bits <SLOPE[3:0]> from 0 to 500 ms. Same slope time is used for

sloping up and down. Advanced slope makes brightness changes smooth for the eye. Dithering can be

programmed with EEPROM bits <DITHER[1:0]> from 0 to 3 bits. Example below is for 1-bit dithering, e.g., for 3-

bit dithering, every 8th pulse is made 1 LSB longer to increase the average value by 1/8 of LSB.

Figure 18. Sloper Operation

Figure 19. Example of the Dithering,

1-bit dither, 10-bit resolution

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