iMX7 dual - Temperature issue

[yuvarajviswanat]

Hi,

We are facing a temperature issue in iMX7 dual processor (commercial).The part number is "MCIMX7D7DVM10SC". The processors undergoes thermal shutdown at 60'C (ambient) with just a single Ethernet interface operating @ 100Mbps. Later I repeated the experiment with iMX7-Sabre SD and Nitrogen boards and got the results mentioned below.

Table.1 Results of Experiments

Board	Sabre SD	Our Product	Nitrogen
Interface running	Ethernet x1 @100Mbps	Ethernet x1 @100Mbps	Ethernet x1 @100Mbps
Ambient Temperature	67.3'C	63.5'C	82'C
Die temperature @Thermal shutdown	90'C	90'C	105'C(Industrial processor)
Temperature on processor package top @Thermal shutdown	83.3'C	83.7'C	97.3'C

The total power consumed by our product is 1W (Max). As per the datasheet specification the Junction to Package temperature is 0.2'C/W (shown in below table).

The expected temperature difference between the Die temperature and the Temperature on the processor package must be 0.2'C (for our case). But from  table.1 it is clear that the difference is too large.

Moreover the CPU load is about 30-35%.

Looking forward for suggestions.

Thanks for your interest,

Yuvaraj

[igorpadykov]

Hi Yuvaraj

suggestions for controlling chip temperature are provided in

AN4579 i.MX6 Series Thermal Management Guidelines (also valid for i.MX7)

https://www.nxp.com/docs/en/application-note/AN4579.pdf 

As processor operates at 60'C ambient temperature, it temperature will be

higher by "Junction to Ambient" factor using Table.1 (upper two rows) .

In Linux Thermal driver handles processor temperature, it is described in

Chapter 25 Thermal Driver attached Linux Manual.

Best regards
igor
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