In described examples of a device with built-in-self-test, a multiplexer has at least first and second input terminals and is coupled to receive a first input signal at the first input terminal, a second input signal at the second input terminal, and selection signals. Also, the multiplexer is coupled to output: the first input signal in response to a first combination of the selection signals; the second input signal in response to a second combination of the selection signals; and an analog summation of the first and second input signals in response to a third combination of the selection signals.