Electromagnetic noise coupling and mitigation for fast response on-die temperature sensing in high power modules

A heavy low pass filter is usually applied to an on-die temperature sensor's output to filter out the strong noises during switching transients. Aiming at high bandwidth junction temperature sensing, this paper evaluates the electromagnetic noise coupling of an on-die temperature sensing diode in a high power module. Challenges of fast response on-die temperature sensing are reviewed first. Noise coupling mechanisms are analyzed under different grounding configurations and operating conditions. Based on the analysis, a method is proposed to estimate the parasitic capacitance between the sensor and the power device. Special attention has been paid to achieve a high bandwidth and noise immunity test setup. With that, the sensor coupled noises are evaluated in experiments and compared with the model. Noise propagation impedance compensation is applied and verified by experiment. Considerations of sensing circuit design are also discussed. A 100 kHz low pass filter is used to deal with the residual noises during switching transients. With the designed sensing circuitry, short circuit tests are conducted to demonstrate sensor's dynamic response.