A high accuracy bandgap reference with adaptive mechanical stress compensation

Mechanical stress due to packaging and soldering process is a random non-ideal factor which has been annoying the design of high accuracy analog ICs for a long time. Soldering and mechanical stress would make trimming meaningless after packaging in bandgap reference (BGR) circuits. This paper proposes adaptive stress compensation technique for high accuracy BGR design. This is implemented by feeding the bandgap circuit with a compensation current extracted from the difference of the base-emitter junctions’ voltage ($V_{BE}$) variations between NPN and PNP bipolar transistors experiencing the same stress. It was found that the temperature coefficient variations caused by soldering can be enhanced by a factor of 45.3%. The measured temperature coefficient of the reference voltage before soldering is 7.02 ppm/°C, while it is 24.73 ppm/°C after soldering. The proposed compensation technique reduced the measured reference voltage temperature coefficient to 15.03 ppm/°C.