Jetson Tx2 Tegra Junction Temperature


I am using Jetson tx2 nx at outdoors environment with ~99% gpu usage and ~80% average all cpu usage. I am trying to figure out the junction temperature inside the tegra x2 silicone and i read the “bcpu-therm” value as dictated in chapter 4 of the thermal management design guide. The problem is i am getting relatively low values. They are similar to all other temperature values and only a few degrees higher then “Tboard_tegra” which i assume is the pcb temperature. The “bcpu-therm” is also only ~35 degrees higher then the ambient which seems relatively low. The ambient is ~25 degrees and bcpu-terms reading gives me ~60 degrees only.

According to my experience the junction temperature inside a silicone chip tends to be much higher. What am I missing and how to read the junction temperature of the tegra x2 correctly?


As showed below info in Thermal Design Guide in DLC.

The Tegra X2 junction temperature can be directly read from sysfs nodes, as shown in the following example. Note that the name of each temperature zone is noted in the type node and that the temperature values are reported in units of m °C.

cat /sys/devices/virtual/thermal/thermal_zone1/type
cat /sys/devices/virtual/thermal/thermal_zone1/temp

Thanks for the reply

This is exactly what I did. The thing is i receive around 60 degrees of junction temperature which is almost the same as the board temperature and only 35 degrees above the ambient. All this while the CPUs and the GPU are working hard.

My question is, whether this data accurate? Junction temperature is usually much higher in such cases and the data seems odd to me.

It is accurate if no hardware issue.

The reason I am investigating the topic is because I am trying to compare the thermal performance of Jetson TX2 and Jetson TX2 NX.

In order to do so I am stressing the devices with same power input and compare the junction temperatures. If I understand right, jetson tx2 and jetson tx2nx should be exactly the same in terms of the CPUs and the GPUs. Despite that, the values that I get are as follows:

For Jetson TX2:
Average input power (from /sys/bus/i2c/drivers/ina3221x/0-0041/iio_device/in_power0_input): 13500mW
Both CPU and GPU are around 85% performance
Average T junction (from cat /sys/devices/virtual/thermal/thermal_zone1/temp): 61 degrees Celsius, about 35 degrees temperature rise above ambient

For Jetson TX2 NX:
Average input power (from /sys/devices/3180000.i2c/i2c-2/2-0040/iio:device0/in_power0_input): 13500mW
Both CPU and GPU are around 85% performance
Average T junction (from cat /sys/devices/virtual/thermal/thermal_zone1/temp): 87 degrees Celsius, about 60 degrees temperature rise above ambient

How is it possible that same SoC provides such a different T junction values under the same ambient temperature and input power?

The Tj also depends on the thermal solution. It is not strange with such difference.

Could you please elaborate more about the thermal solution?
Any information you could share about the TTP and the TIM of the jetson tx2 in addition to the one in the design guide will be highly appriciated

You can refer to below TX2 and TX2 NX TDG for thermal related info. Also you can share the photo of your TX2 and TX2 NX board so that we can see the thermal solution difference.

Jetson TX2 Series Thermal Design Guide
Jetson TX2 NX Thermal Design Guide

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