1 Introduction

Current measurement systems are experiencing rapid adoption as global electrification accelerates. These systems serve critical functions including feedback control, overcurrent protection, GaN FET zero-crossing detection, and advanced monitoring applications. In parallel, power density continues to be of chief importance, with solutions for various products chasing increasingly smaller footprints with each generation. This combination of trends creates a challenging thermal environment: as power density increases, component density rises, printed circuit board copper content decreases because of shrinkage, and ambient temperatures increase from cumulative heat generation. Accurately determining the maximum safe operating limits for semiconductor devices has become essential for reliable system design.

This paper examines the behavior of junction temperature in the DVF package used for the TMCS114x product series across multiple reference frames. For a characterization of junction temperature, the paper presents both a traditional current-based approach through curve of best fit, and alternative characterization methods examining the superposition of the power generated by the part itself as well as the power produced in the lead frame. Current remains the typical value provided to end users for defining safe operating areas, but its applicability varies significantly based on board construction. However, the current-based approach continues to dominate industry standards. If a design maintains steady-state operation at the maximum current specification, thermal considerations can typically be deprioritized from a reliability perspective.

As an alternative approach, this paper characterizes junction temperature through direct measurement of ambient temperature and lead frame temperature. This is accomplished by examining both heat sources internal to the device: the quiescent power of the silicon itself, as well as the power developed in the lead frame. This is accomplished using the ISOTMP35R reinforced isolated temperature sensor integrated circuit. The ISOTMP35R integrates an isolation barrier with a 5kVRMS withstand voltage and combines an analog temperature sensor featuring a 10mV/°C slope across the operating range of −40°C to 150°C. While still tested to the original layout of the standard TMCS family evaluation modules, this approach provides the user an application based approach for more granular monitoring and control of the junction temperature. This paper examines both the traditional current-based methodology via best fit curve, and the alternative junction temperature characterization approach.