An encoder is provided for converting thermometer code data with bubbles to binary format. An integrated circuit may have circuitry such as digital phase-locked loop circuitry. A thermometer code data word may be used as a control signal for the circuitry. It may be desirable to monitor the thermometer code data word for testing or for downstream processing by control logic on the integrated circuit. The encoder performs thermometer code to binary encoding without requiring that the thermometer code be error corrected to remove bubbles. A bubble detection circuit may be used to detect when the thermometer code data contains bubbles. The encoder may use carry look-ahead adders and pipeline stages.