ZHCSOB3D November 1998 – June 2021 CD54HC126 , CD74HC126
PRODUCTION DATA
In this application, a 3-state buffer is used to enable or disable a data connection as shown in GUID-F1C85FF8-3AAE-47F5-8D86-8A92C1E535B2.html#APP1_SCHEM. It is common to see all four channels of a device used together for controlling a 4-bit data bus, however each channel of the device can be used independently. Unused channels should have the inputs terminated at ground or VCC and the output left unconnected.
When the output of the device is active, the data signal will be replicated at the output. When the output of the device is disabled, the output will be in a high-impedance state, and the output voltage will be determined by the circuit connected to the output pin. This circuit is most commonly used when a bus must be completely disabled. One example of this situation is when the circuitry connected to the output is to be powered off for an extended period of time to save system power, and the inputs to that circuitry cannot have a voltage present due to protective clamp diodes.