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TCA6408_09 Datasheet, PDF (22/31 Pages) Texas Instruments – LOW-VOLTAGE 8-BIT I2C AND SMBus I/O EXPANDER WITH INTERRUPT OUTPUT, RESET, AND CONFIGURATION REGISTERS | |||
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TCA6408
LOW-VOLTAGE 8-BIT I2C AND SMBus I/O EXPANDER
WITH INTERRUPT OUTPUT, RESET, AND CONFIGURATION REGISTERS
SCPS151C â FEBRUARY 2007 â REVISED JUNE 2007
www.ti.com
APPLICATION INFORMATION (continued)
Minimizing ICC When the I/O is Used to Control LEDs
When the I/Os are used to control LEDs, normally they are connected to VCC through a resistor as shown in
Figure 14. The LED acts as a diode so when the LED is off the I/O VIN is about 1.2 V less than VCC. The âICC
parameter in "Electrical Characteristics" shows how ICC increases as VIN becomes lower than VCC. Designs
needing to minimize current consumption, such as battery power applications, should consider maintaining the
I/O pins greater than or equal to VCC when the LED is off.
Figure 15 shows a high-value resistor in parallel with the LED. Figure 16 shows VCC less than the LED supply
voltage by at least 1.2 V. Both of these methods maintain the I/O VIN at or above VCC and prevent additional
supply current consumption when the LED is off.
VCC
VCC
Px
LED
100 kâ¦
Figure 15. High-Value Resistor in Parallel With the LED
3.3 V
5V
VCC
Px
LED
Figure 16. Device Supplied by a Low Voltage
22
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