PCA9534A Datasheet, PDF (22/35 Pages) Texas Instruments – REMOTE 8-BIT I2C AND SMBus LOW-POWER I/O EXPANDER WITH INTERRUPT OUTPUT AND CONFIGURATION REGISTERS

PCA9534A
REMOTE 8-BIT I²C AND SMBus LOW-POWER I/O EXPANDER
WITH INTERRUPT OUTPUT AND CONFIGURATION REGISTERS
SCPS141B – SEPTEMBER 2006 – REVISED MARCH 2007
www.ti.com
APPLICATION INFORMATION (continued)
Minimizing I_CC When the I/O Controls LEDs
When the I/Os are used to control LEDs, they are normally connected to V_CC through a resistor as shown in
Figure 14. Because the LED acts as a diode, when the LED is off, the I/O V_IN is about 1.2 V less than V_CC. The
supply current, I_CC, increases as V_IN becomes lower than V_CC and is specified as ∆I_CC in Electrical
Characteristics.
For battery-powered applications, it is essential that the voltage of the I/O pins is greater than or equal to V_CC
when the LED is off to minimize current consumption. Figure 15 shows a high-value resistor in parallel with the
LED. Figure 16 shows V_CC less than the LED supply voltage by at least 1.2 V. Both of these methods maintain
the I/O V_IN at or above V_CC and prevents additional supply-current consumption when the LED is off.
V_CC
V_CC
LEDx
LED 100 kW
Figure 15. High-Value Resistor in Parallel With the LED
3.3 V
5V
V_CC
LED
LEDx
Figure 16. Device Supplied by a Lower Voltage
22
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