SCPS193C July 2010 – April 2014 TCA6424A
Figure 29 shows an application in which the TCA6424A can be used.
When the I/Os are used to control LEDs, normally they are connected to VCC through a resistor as shown in Figure 29. 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 ΔICC parameter in Electrical Characteristics shows how ICC increases as VIN becomes lower than VCC. Designs that must 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 30 shows a high-value resistor in parallel with the LED. Figure 31 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.