1 Introduction

With the advent of RF CMOS and Antenna on packaging technology brings in the massive integration of complete mmWave sensor solution to extreme form factor level of the order of few 10s of mm. This solution includes mmWave sensor, PMIC, USB2.0 interface, clocking, external Flash interface and passive devices.

This enables a lower cost system solution, however, entire sensor dissipates close to 2.5W-3W power in such a small form factor design, compounds the thermal design problem. In this AOP mmWave sensor junction temperature needs to be kept under 105°C for Industrial and 125°C for automotive use-cases under all conditions.

This application report goes through the thermal design guide for AoP-based mmWave sensors and identifies the thermal hot-spots in the design and mitigates it through development of various techniques such as different duty cycles trade-off for power dissipation under various application scenarios. This includes the PCB sizes trade-off with the junction temperature, board design guideline for mitigating thermal aspects.

If the sensor requires higher performance with higher duty cycles, then heatsink designs will be explored depending upon use-case requirements and Board/System level optimizations.

This document also covers lesson learning through measurements, useful tips for the thermal design, also dwells on the PCB level thermal mitigation technique to dissipate the heat to keep the junction temperature under safe thermal limit.