LP3954TLXSLASHNOPB datasheet(29/58 Pages) TI2

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VDDA

AMBIENT

LIGHT

SENSOR

AIN

IBIAS

1 PA

ADC

VDDA

100

TIME (s)

0.7

0.1

0.2

0.3

0.4

0.5

0.6

FADE OUT

FADE IN

100

TIME (s)

1.4

0.2

0.4

0.6

0.8

0.1

1.2

FADE OUT

FADE IN

LP3954

www.ti.com

SNVS340D – JUNE 2005 – REVISED MARCH 2013

Figure 29. WLED Dimming, SLOPE=0

Figure 30. WLED Dimming, SLOPE=1

Ambient Light and Temperature Measurement with LP3954

The Analog-to-Digital converter (ADC) in the Audio Syncronization block can be also used for ambient light

measurement or temperature measurement.

The selection between these modes is controlled with input selector bits INPUT_SEL[1:0] as follows

INPUT_SEL[1:0]

Mode

Audio synchronization

Temperature measurement

(voltage input)

Ambient light measurement

(current input)

No input

AMBIENT LIGHT MEASUREMENT

The ambient light measurement requires only one external component: Ambient light sensor (photo transistor or

diode). The ADC reads the current level at ASE pin and converts the result in digital word. User can read the

ADC output from the ADC output register. The known ambient light condition allows user to set the backlight

current to optimal level thus saving power especially in low light and bright sunlight condition.

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