Online die temperature measurement using S-parameters in GaN-based power converters

Die temperature (Tj) measurement of GaN HEMTs is of high interest to enable reducing design margin and the implementation of reliability driven control schemes and protections. On-state resistance (Rds,on) has been identified as a relevant thermo-electric sensitive parameter (TSEP) for Tj measurement requiring no extra temperature sensor. It is commonly measured in time-domain, based on the on-state voltage drop and the load current. In this work, the Tj of a GaN-on-Si power IC in a dc-dc converter is deduced from measurements conducted online, directly in the frequency domain using RF injection and S-parameter measurements. Thereby, the stimulus is injected on top of the processed power to probe either Rds,on, or the resistance of an on-chip Schottky diode used as thermal sensor. Temperature dependent experimental validation up to 150 ◦C is performed on a switching dc-dc power converter, validating the approach for online temperature measurement using RF injection.