LP8555 datasheet(17/64 Pages) TI1

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CURRENT CONTROL

(THRESHOLD = 000b)

CURRENT CONTROL

100%

Max Current can be set with <MAXCURR>

EPROM Bits or RISET Resistor

100%

PWM & CURRENT CONTROL with

Switch Point of 25% of ILED_MAX

(THRESHOLD = 101b)

PWM CONTROL

CURRENT CONTROL

25%

50%

100%

Max Current can be set with <MAXCURR>

EPROM Bits or RISET Resistor

100%

25%

Brightness (Controlled

with PWM Input Duty)

PWM CONTROL

(THRESHOLD = 111b)

25%

50%

100%

Max Current can be set with <MAXCURR>

EPROM Bits or RISET Resistor

Brightness (Controlled

with PWM Input Duty)

LP8555

www.ti.com

SNVS857 – FEBRUARY 2014

8.3.2.6 Hybrid PWM and Current Dimming Control

Hybrid PWM and Current Dimming control combines PWM dimming and LED current-dimming control methods.

With this dimming control, it is possible to achieve better optical efficiency from the LEDs compared to pure PWM

control while still achieving smooth and accurate control and low brightness levels. The switch point from current-

to-PWM control is set with THRESHOLD EPROM field, available settings are Pure PWM dimming (THRESHOLD

= 111b), 25% switch point (THRESHOLD = 101b) and Pure Current Dimming (THRESHOLD = 000b). 25%

setting allows good compromise between good matching of the LEDs brightness/white point at low brightness

and good optical efficiency.

Figure 28.

Figure 29.

Figure 30.

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