In described examples, an integrated circuit includes an on-off keying (OOK) digital isolator, which includes a first circuitry, a multiplexer, an OOK modulator, an isolation barrier, an OOK envelope detector, and a second circuitry. The first circuitry generates and outputs a calibration signal. The multiplexer has a data signal input, and an input coupled to a first circuitry output. An OOK modulator input is coupled to a multiplexer output. An isolation barrier input is coupled to an OOK modulator output. An OOK envelope detector input is coupled to an isolation barrier output. The second circuitry includes an input coupled to an OOK envelope detector output, and an output coupled to an OOK envelope detector control input. The second circuitry detects a duty cycle distortion (DCD) of the OOK envelope detector output, and outputs a control signal to change the OOK envelope detector output's duty cycle based on the detected DCD.