PCA9534RGVR datasheet(22/32 Pages) TI

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Minimizing I

CC When the I/O Controls LEDs

LED

LEDx

VCC

100 kW

VCC

LED

3.3 V

5 V

LEDx

VCC

PCA9534

REMOTE 8-BIT I2C AND SMBus LOW-POWER I/O EXPANDER

WITH INTERRUPT OUTPUT AND CONFIGURATION REGISTERS

SCPS124B – SEPTEMBER 2006 – REVISED FEBRUARY 2007

APPLICATION INFORMATION (continued)

When the I/Os are used to control LEDs, they are normally connected to VCC through a resistor, as shown in

Figure 14. Because the LED acts as a diode, when the LED is off, the I/O VIN is about 1.2 V less than VCC. The

supply current, ICC, increases as VIN becomes lower than VCC and is specified as ∆ICC in Electrical

Characteristics.

For battery-powered applications, it is essential that the voltage of the I/O pins is greater than or equal to VCC

when the LED is off to minimize current consumption. 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 prevents additional supply-current consumption when the LED is off.

Figure 15. High-Value Resistor in Parallel With the LED

Figure 16. Device Supplied by a Lower Voltage

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