JAJSN80E August 2009 – May 2022 TCA9535
When an I/O is used to control an LED, normally it is connected to VCC through a resistor as shown in Figure 8-1. 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 ΔICC parameter in the Electrical Characteristics table shows how ICC increases as VIN becomes lower than VCC. For battery-powered applications, it is essential that the voltage of I/O pins is greater than or equal to VCC when the LED is off to minimize current consumption.
Figure 8-2 shows a high-value resistor in parallel with the LED. Figure 8-3 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 prevent additional supply current consumption when the LED is off.