SCPS124H September 2006 – March 2021 PCA9534
When the I/Os are used to control LEDs, they are normally connected to VCC through a resistor, as shown in Figure 10-1. 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 ΔICC 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 10-2 shows a high-value resistor in parallel with the LED. Figure 10-3 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.