Is the E3845's Core Temperature with DTS value saturated at low ambient temperature?

[SChoi8]

Hi,

I use E3845.

And I measure CPU core temperature with DTS value.

I think the Tj-max of the E3845's core is 110 degree Celsius.

So, If DTS value is 127, I assume the core temperature is 110.

But, the kernal function just return's the relative value (k= DTS - 127 ),

so I calculate as follows,

Tcore = Tj-max - k;

According to Chapter 8' table 62 and its note, of family datasheet,

if DTS =127, then the temperature is 110, and DTS 137, then the temperature is 90, and so forth.

This means Tcore = Tj-max - k*2. But anyway I use" Tcore = Tj-max - k" formula.

Now, my problem is this,

When I put the board into chamber, and set the temperature as -40 degree Celsius.

And wait for more than one hour with borad power off, I measure the core temperature just after booting up, but the result was just -9 degree Celsius.

Under -50 degree Celsius environment, the result was same.

What is the reason of this kind of low temperature limitation ?

Dis you experience this kind of saturation?

Or just I use wrong formula for core temperature measurement ?

Thank you for reading this article.

[idata]

Hi, Sunghyuk_Choi, Thank you very much for joining the Intel® processors communities.

Correct, you are right, the Tj-max of the Intel® Atom™ Processor E3845 is 110 degree Celsius, -40°C to 110°C:http://ark.intel.com/products/78475/Intel-Atom-Processor-E3845-2M-Cache-1_91-GHz http://ark.intel.com/products/78475/Intel-Atom-Processor-E3845-2M-Cache-1_91-GHz I checked the datasheet of the processor, and on chapter 8 I did not see table 62, I found table 65 and it shows different values from the ones you described above, it shows that if the DTS is 127 then the temperature read is 90°C, if the DTS is 137 then the temperature read is 80°C, page 113:http://www.intel.com/content/www/us/en/embedded/products/bay-trail/atom-e3800-family-datasheet.html http://www.intel.com/content/www/us/en/embedded/products/bay-trail/atom-e3800-family-datasheet.html In order to provide the most accurate response to your inquiries, we will do further research on this matter, and as soon as I get any information about this subject, I will post all the details on this thread. Any further questions, please let me know. Regards,Alberto

[SChoi8]

Thank you very much for your reply.

My datasheet version was 3.6.

And, I found out the latest version is 4.1.

According to the latest version datasheet chapter 8. table 65, exactly the "Note" of the table 65,

there are "Note:DTS encoding of 127 always represents TJ-MAX.If TJ-MAX is at 110°C instead of 90°C

then the encoding 127 from DTS indicates 110°C, 137 indicates 90°C and so forth."

Please attention to the last sentence.

If Tj-max is 110°C with DTS value 147, then the temperature is 70 °C ?

I want to know this.

Regards,

Choi

[idata]

Sunghyuk_Choi, You are very welcome. To answer your question, yes that is correct, based on the formula provided on the data sheet, if the If Tj-max is 110°C with DTS 147 then the temperature reading will be 70 °C:

DTS Temperature127 110 °C137 90 °C147 70 °C Any questions, please let me know. Regards,Alberto

[idata]

Sunghyuk_Choi, I just received some updates from the research we did on this subject, and in this case in order to get the information you are requesting please visit our Embedded Design Center site, they should be able to further assist you with the information you are looking for:

https://embedded.communities.intel.com/community/en/ https://embedded.communities.intel.com/community/en/Any questions, please let me know. Regards,Alberto