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Intensity Control

Examples of Intensity Control

TCA6507

WITH INTENSITY CONTROL AND SHUTDOWN

SCPS164B – MAY 2007 – REVISED NOVEMBER 2007

The Maximum Intensity registers must be written to for setting the intensity of the LED. This register has eight

bits – top four bits for BANK1 (or PWM1) and bottom four bits for BANK0 (or PWM0). This register can be written

to after sending data to the Second Fully-Off Time register (see Table 17).

The Maximum Intensity register has a default value of 15 (1111), which translates to 100% brightness (see

Figure 7 and Table 15).

The intensity of the LED can be modified by changing the duty cycle of the output port voltage. The period is 8

ms. In Figure 8, 1111 0000 was written into the Maximum Intensity register to put a 100% intensity level in

PWM1 or BANK1.

The user can vary the duty cycle of the output voltage for intensity changes:

• For 25% brightness, the voltage level at the output/LED should be LOW for 25% of the time (2 ms) and HIGH

for 75% of the time (6 ms).

• For 75% brightness, the voltage level at the output/LED should be LOW for 75% of the time (6 ms) and HIGH

for 25% of the time (2 ms).

In Figure 8, 0111 0000 was written into the Maximum Intensity register to put a 50% intensity level in PWM1 or

BANK1. The period is 8 ms.

The user can vary the duty cycle of the output voltage for intensity changes:

• For 12.5% brightness, the voltage level at the output/LED should be LOW for 12.5% of the time (1 ms) and

HIGH for 87.5% of the time (7 ms).

• For 37.5% brightness, the voltage level at the output/LED should be LOW for 37.5% of the time (3 ms) and

HIGH for 62.5% of the time (5 ms)

Copyright © 2007, Texas Instruments Incorporated

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