LP8556 datasheet(20/52 Pages) TI

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PWM CONTROL

CURRENT CONTROL

25%

100%

Max current is set with CURRENT and CURRENT_MAX EPROM bits

or CURRENT and CURRENT_MAX EPROM bits and RISET resistor

25%

50%

100%

PWM & CURRENT CONTROL with Switch Point at 25% of ILED_MAX

(PWM_TO_I_THRESHOLD = 0111b)

BRIGHTNESS

50%

LP8556

SNVS871B – JULY 2012 – REVISED SEPTEMBER 2012

www.ti.com

Adaptive Control

Adaptive dimming control combines PWM Control and Pure Current Control dimming methods. With the adaptive

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

still achieving smooth and accurate control at low brightness levels. Current resolution in this mode is 12-bits.

Switch point from Current to PWM control can be set with the PWM_TO_I_THRESHOLD EPROM field from 0%

to 100% of the brightness range to get good compromise between good matching of the LEDs brightness/white

point at low brightness and good optical efficiency.

PWM frequency is set either using an external set Resistor (RFSET) or using the PWM_FREQ EPROM bits. The

maximum LED current is set either using an external set Resistor ( RISET) and CURRENT and CURRENT_MAX

EPROM bits or just using the CURRENT and CURRENT_MAX EPROM bits.

Figure 23. Adaptive Output Dimming Scheme

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LP8556 Datasheet(PDF) 20 Page - Texas Instruments