OSD335x-BAS Thermal Guide

Published On: March, 1, 2018 By: Eshtaartha Basu | Updated: July 18, 2018 by Cathleen Wicks

The temperature of a device during operation in a system is an important parameter as it affects many properties such as device functionality, reliability and life. Since OSD335x is a System-in-Package (SiP) with several ICs and passive components, single IC package data cannot be used to estimate its thermal characteristics. Hence, it was necessary to characterize OSD335x SiP for its thermal behavior.

This document will provide thermal characteristics of OSD335x and a way to estimate junction temperature. We will also give a comparison of OSD335x with a similar system of discrete components.

Table of Contents

1. Comparison of OSD335x with Discrete Components
2. OSD335x Thermal Parameters
3. Measuring Case Temperature and Estimating Junction Temperature of the OSD335x SiP

A PDF version of this App Note can be found here.

Notice

The information provided within this document is for informational use only. Octavo Systems provides no guarantees or warranty to the information contained.

1. Comparison of OSD335x with Discrete Components

One of the questions we seek to know is how SiP temperatures compare with a similar system that has individual components in it.

Figure 1 shows case temperature of AM3358 at approximately 99% CPU Load on a board that had individual components mounted and Figure 2 shows case temperature of OSD335x (focused on AM3358 die) under same load. We can see that OSD335x case temperature is less (approximately 49.7°C ) compared to that of AM3358 for the same load (approximately 53.1°C).

2. OSD335x Thermal Parameters

The measured Thermal Parameters of OSD335x are given in Table 1.

⁽¹⁾ is the measured Thermal Resistance from Junction to Top of Package as measured above the CPU when the SiP is mounted on a 6 layer board (SBC Reference Design Board) in still air and CPU under maximum load, and other components operating per spec.

⁽²⁾ is the measured Thermal Resistance from Junction to Ambient Air when the SiP is mounted on a 6 layer board (SBC Reference Design Board) in still air and CPU under maximum load, and other components operating per spec.

3. Measuring Case Temperature and Estimating Junction Temperature of the OSD335x SiP

To measure the case temperature of OSD335x SiP:

1. Tools needed: Thermocouple (Perfect-Prime TL0225 surface contact, 0.25mm diameter with K-Type Sensor Probe) or FLIR ONE PRO Thermal Camera.
2. Calibrate thermocouple or other temperature-measuring device such as FLIR ONE PRO with known temperatures such as ice-cold water and boiling water.
3. Place the SiP in an enclosure so that there are no stray air currents while making measurements and run the desired application on it.
4. Make contact or fix the thermocouple on the package or focus FLIR ONE PRO on the package. For thermocouples, make sure of good contact with the top surface of the SiP using thermal grease.
5. Record the case temperature (T_C) once the temperature is stabilized.
6. Measure the input power (P) consumed by the SiP.
7. Case temperature (T_C) thus obtained may be used to verify if the SiP is operating under conditions specified in the datasheet.

It may be desirable to estimate the Junction Temperature (T_J) of the AM3358 Die inside the System-in-Package. In this case it can be estimated with the following equation:

The OSD335x-SM Thermal Guide can be found HERE

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