LM3533 Datasheet, PDF(28/53 Page) Texas Instruments – Complete Lighting Power Solution for Smartphone Handsets

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LM3533 Datasheet, PDF (28/53 Pages) Texas Instruments – Complete Lighting Power Solution for Smartphone Handsets

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LM3533

DELAY TIME

The Delay time (tDELAY) is the delay from when the pattern is enabled to when the LED current begins ramping up in the control

bank's assigned current source(s). The pattern starts when bit [3] of the respective Control Bank Brightness Configuration Register

is written high. There is one tDELAY register for each pattern generator (4 total). The selectable times are programmed with the lower

6 bits of the tDELAY registers. The times are split into 2 groups where codes 0x00 to 0x3C are short durations from 16.384ms (code

0x00) up to 999.424ms (code 0x3C) or 16.384ms/bit. The higher codes (0x3D to 0x7F) select tDELAY from 1130.496ms up to

9781.248ms, or 131.072ms/bit (see Table 35).

RISE TIME

The LED current rise time (tRISE) is the time the LED current takes to move from the low-current brightness level (ILOW) to the high-

current brightness level (IHIGH). The rise time of the LED current (tRISE) is set via the Pattern Generator Rise Time Registers. Each

Pattern Generator has its own rise-time register. There are 8 available rise-time settings (see Table 42).

FALL TIME

The LED current fall time (tFALL) is the time the LED current takes to move from the high-current brightness level (IHIGH) to the low-

current brightness level (ILOW). The fall time of the LED current (tFALL) is set via the Pattern Generator Fall Time Registers. Each

Pattern Generator has its own fall-time register. There are 8 available fall-time settings (see Table 43).

HIGH PERIOD

The LED current high period (tHIGH) is the duration that the LED pattern spends at the high LED current set point (tHIGH). The

tHIGH times are programmed via the Pattern Generator tHIGH Registers. The programmable times are broken into 2 groups. The first

set (from code 0x00 to 0x3C) increases the tHIGH time in steps of 16.384ms. The second set (from code 0x3D to 0x7F) increases

the tHIGH time in steps of 131.072ms (see Table 39).

LOW PERIOD

The LED current low period (tLOW) is the duration that the LED current spends at the low LED current set point (ILOW). The tLOW

times are programmed via one of the Pattern Generator tLOW Registers. There are 256 tLOW settings and are broken into 3 groups

of linearly increasing times. The first set (from code 0x00 to 0x3C) increases the tLOW time in steps of 16.384ms. The second set

(from code 0x3D to 0x7F) increases the tLOW time in steps of 131.072ms. The third set (from code 0x80 to 0xFF) increases the

tLOW time in steps of 524.288ms (see Table 37).

LOW-LEVEL BRIGHTNESS

The LED current low brightness level (ILOW) is the LED current set point that the pattern rests at during the tLOW period. This level

is set via the Pattern Generator Low Level Brightness Register(s). The brightness level has 8 bits of programmability. ILOW is a

function of the Control Banks full-scale Current setting, the code in the Pattern Generator Low-Level Brightness Register, the

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

For exponential mapping ILOW is:

For linear mapping ILOW is:

BREGL_X is the Pattern Generator Low-Level Brightness Register setting for the specific Control Bank (see Table 40).

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