main[7:0]

en_main

8-Bit IDAC

en_main_pwm

External PWM

&

MAIN

VBOOST

VBOOST

sub[7:0]

en_sub

8-Bit IDAC

en_sub_pwm

External PWM

&

SUB

VBOOST

LP3958

www.ti.com

SNVS423C – JANUARY 2006 – REVISED MARCH 2013

Figure 17. SUB output for 2 LEDs (DISPL = 0)

Figure 18. MAIN and SUB outputs for 8 LEDs (DISPL = 1)

PWM CONTROL

External PWM control is enabled by writing 1 to EN_MAIN_PWM and/or EN_SUB_PWM bits in register address

2BH. GPIO[0] pin is used as external PWM input when EN_PWM_PIN is set high. PWM input is active high, i.e.

LED is activated when in high state.

FADE IN / FADE OUT

LP3958 has an automatic fade in and out for main and sub backlight. The fade function is enabled with

EN_FADE bit. The slope of the fade curve is set by the SLOPE bit. Fade control for main and sub display is set

by FADE_SEL bit.

Recommended fading sequence:

1. ASSUMPTION: Current WLED value in register

2. Set SLOPE

3. Set FADE_SEL

4. Set EN_FADE = 1

5. Set target WLED value

Copyright © 2006–2013, Texas Instruments Incorporated

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Product Folder Links: LP3958