LM3532 datasheet(22/52 Pages) TI2

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VALS_

Current Average

Zone

*Note:it takes a

full average

period to

generate an

averager

output value

ILED

Zone 3 Brightness Target

Averager Ouput

Enable ALS

ALS Fast

Start-Up

Zone 4

Zone 3

Zone 2

Zone 1

Zone 0

Zone 4 Brightness Target

Average

Period #

Zone 2 Brightness Target

LM3532

SNVS653E – JULY 2011 – REVISED AUGUST 2015

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3. The second average period the ALS averages to Zone 2. The Averager Output remains at Zone 3.

4. The 3rd through 7th average period the ALS input averages to Zone 2, and the Averager Output stays at

Zone 2.

5. The 8th average period the ALS input averages to Zone 4. The Averager Output remains at Zone 2.

6. The 9th and 10th average periods the ALS input averages to Zone 4. The Averager Output is at Zone 4.

Because the Averager Output increased from Zone 2 to Zone 4 and the required Down Delay time was not

met (8 average periods), the backlight current was never changed to the Zone 2's target current.

7. The 11th average period the ALS input averages to Zone 2. The Averager Output remains at Zone 4.

Because this is the 3rd consecutive average period where the Averager Output has shown a change since

the change from Zone 2, the backlight current transitions to Zone 4's target current.

8. The 12th through 26th average periods the ALS input averages to Zone 2. The Averager Output remains at

Zone 2. At the start of average period 20 the Down Delay algorithm has shown the required 8 average period

delay from the initial change from Zone 4 to Zone 2. As a result the backlight current is programmed to Zone

2's target current.

Figure 20. ALS Down-Delay Control

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