LM3533 Datasheet, PDF(29/53 Page) Texas Instruments – Complete Lighting Power Solution for Smartphone Handsets

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LM3533 Datasheet, PDF (29/53 Pages) Texas Instruments – Complete Lighting Power Solution for Smartphone Handsets

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LM3533

HIGH-LEVEL BRIGHTNESS

The LED current high brightness level (IHIGH) is the LED current set point that the pattern rests at during the tHIGH period. This high-

current level is set via the Control Banks Brightness Register (BREGCH-BREGFH). The brightness level has 8 bits of programma-

bility. IHIGH is a function of the Control Banks Full-Scale Current setting, the code in the Control Banks Brightness Register, the

Mapping Mode selected, and the PWM input duty cycle (if PWM is enabled).

For exponential mapping IHIGH is:

For linear mapping IHIGH is:

BREGH_X is the Control Banks Brightness Register setting for the specific Control Bank (see Table 28 ).

ALS CONTROLLED PATTERN CURRENT

The current levels (IHIGH and ILOW) of the programmable pattern can also be influenced by the ALS input. All the same ALS algorithms

apply to the pattern generator current levels (Direct, Up Only, and Down Delay). The difference, however, for the ALS Controlled

Pattern Current is that the pattern current is not changed to zone-defined brightness targets, but is changed by a scaled factor of

the existing IHIGH and ILOW levels. These scaled factors are programmable in the ALS Pattern Scaler Registers (see Table 17, Table

18 , and Table 19). Each defined brightness zone has a 4-bit (16-level) scale factor, which takes the programmed pattern current

code and multiplies it by the programmed scale factor. This produce a new IHIGH and ILOW current level ranging from 1/16 Ã BREGH

and 1/16 Ã BREGL up to 16/16 Ã BREGH and 16/16 Ã BREGL for each ALS zone (see Figure 15). There is only one set of scale

factors for all the pattern generators.

FIGURE 15. ALS Controlled Pattern Current Scaling

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For low-voltage control banks that do not have their pattern generator enabled, ALS current control is done via the ALS Mappers.

Once a pattern generator is enabled, that particular Control Bank will then use the pattern scalers for ALS Current Control.

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