TCA6507_10 Datasheet, PDF (25/32 Pages) Texas Instruments – LOW-VOLTAGE 7-BIT I2C AND SMBus LED DRIVER WITH INTENSITY CONTROL AND SHUTDOWN

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TCA6507
LOW-VOLTAGE 7-BIT I²C AND SMBus LED DRIVER
WITH INTENSITY CONTROL AND SHUTDOWN
SCPS164B – MAY 2007 – REVISED NOVEMBER 2007
Intensity Control
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).
Examples of Intensity Control
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
Product Folder Link(s): TCA6507
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