SCLS100F December 1982 – April 2021 SN54HC86 , SN74HC86
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
In this application, a 2-input XOR gate is used as a phase difference detector as shown in Figure 9-1. The remaining three gates can be used for other applications in the system, or the inputs can be grounded and the channels left unused.
The device is used to identify phase difference between a reference clock and another input clock. Whenever the clock states are different, the XOR output will pulse HIGH until the clocks return to the same state. The output is fed into a low-pass filter to obtain a DC representation of the phase difference.