Question, i.MX28 internal die temperature

[SLICE]

Dear team,

I would like to ask about i.MX28 internal temperature measurement.

My customer is now using i.MX28 and they are using internal die temperature sensing which is describing at 38.2.2 in your reference manual(MCIMX28RM, Rev.2).

Sometimes they can read the die temperature that is higher than the junction temperature range which is specified in your datasheet. But they believes that the temperature that is got from the sensing scheme includes some error from the actual die temperature. They think they should add the error value to the read temperature to avoid overheating.

Is it true?

If so, please let me know how they should consider to make decision of the threshold temperature value.

Thanks,

Miyamoto

[Yuri]

Hello,

  The following additional information about temperature protection may be helpful :

This feature can be enabled by the following :

1. Enable THERMAL_RESET_ENABLE in HW_CLKCTRL_RESET : 0x800401e0 = 0x8.

2. Enable Thermal module via clear PWD in HW_POWER_THERMAL: 0x80044120 = 0x0  (default is 115 C).

3. Enable XTAL32KHZ_PWRUP in HW_RTC_PERSISTENT0: 0x80056064 = 0x20.

  After doing that, if the AUTO_RESTART bit is set in HW_RTC_PERSISTENT0, when

temperature is over than 115 C, system will reset, and if AUTO_RESTART bit is clear, system

will power off if the device has no 5V connected.

   Note, temperature sensor accuracy is about 10 degree C. NXP Linux BSP supports

the temperature sensor via function ddi_power_GetDieTemp(int16_t *pLow, int16_t *pHigh).

  Also we should distinguish between external ambient temperature and internal junction temperature.

Thermal protection operates with the junction one.

T junction = T ambient + RthJA x PD

where PD is Total On-chip Power Dissipation.

Have a great day,
Yuri

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[SLICE]

Hello Yuri‌

>  Note, temperature sensor accuracy is about 10 degree C.

Can I understand the value that can be obtained from the sensor may include about 10 C degree of error value?

Thanks,

Miyamoto

[Yuri]

Yes, +/-5 degree 

[SLICE]

Hello Yuri‌

According to i.MX28 datasheet, the maximum value of junction temperature for industrial chips is 105 degree C.

I think the default value of 115 degree C comes from the max junction temp plus the error value + marginal values.

Correct?

And

The way to measure temperature used in the thermal-shutdown you mentioned is same as the way mentioned in chapter 38.2.2 in reference manual?

That is;

The results, measured temperatures, are the same?

Best Regards,

Miyamoto

[Yuri]

Hello,

  115 degree C means temperature definitely out of allowed range.  

Examples of code You may find in the following discussion.

https://community.nxp.com/thread/283564 

Regards,

Yuri.

[SLICE]

Hello Yuri‌

Thanks a lot for your support.

The way to measure the temperature for the thermal-shutdown is to use two of physical LRADC channels (which is mentioned at 38.2.2 in your reference manual)?

Right?

Best Regards,

Miyamoto

[Yuri]

yes, two channels.