AM3354: How to calculate the temperature of SOC with appropriate RθJC ψJT?

Zekun Bai

Part Number: AM3354

Tool/software:

As above, we have few questions:

Question 1. The chip is currently designed with heat conduction measures (heat sink + thermal pad), as shown in the figure. In this case, how to calculate the junction temperature of the chip? Which parameter is more applicable, RθJC or ψJT? If ψJT is applicable, what value should ψJT take?

2. Under the condition of heat conduction measures as shown in the figure below, is there any recommendation for the junction temperature calculation method? Please recommend it.

3. Under the condition of heat conduction measures as above, can the junction temperature calculation method and ψJT value experience be applied to other models of digital integrated chips or storage such as DSP, MCU, etc. of TI?

Regards

Zekun

over 1 year ago

0 Kallikuppa Sreenivasa over 1 year ago

TI__Guru**** 191829 points

Hello Zekun,

Thank you for the query.

Please check if the below FAQ helps

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/762959/am5728-overheated-risk-by-increasing-leak-current-in-higher-temperature?tisearch=e2e-sitesearch&keymatch=Tj#

I need to check internally.

Regards,

Sreenivasa

+1 Kallikuppa Sreenivasa over 1 year ago in reply to Kallikuppa Sreenivasa

TI__Guru**** 191829 points

Hello Zekun,

Refer below inputs i received.

It’s not easy to calculate the junction using Rth-JC or Psi-JT in customer setup.

Rjc requires that +90% of power dissipation (PD) was conducted through the top of the package. Under such condition, Tj=Tc + PD * Rth-JC.

Psi-JT requires a non heat sink setup in which almost all power dissipation was conducted through the board. Under such condition, Tj=Tc + PD*Psi-JT

In customer setup, there are two ways dissipation (some through the top heat spreader, some through the board). The distribution is depends on the top resistance (top thermal interface material (TIM) + Heat spreader resistance).

If customer can determine the top resistance, then they can use equation #6 as described in https://www.ti.com/lit/an/spra953d/spra953d.pdf

Here, the Rth-SA is the heat spreader resistance; Rth-CS is the TIM resistance.

Regards,

Sreenivasa

0 Zekun Bai over 1 year ago

TI__Expert 3575 points

Hi Sreenivasa

Thanks, let me check with customer.

Close it for now.

Regards

Zekun

0 Kallikuppa Sreenivasa over 1 year ago in reply to Zekun Bai

TI__Guru**** 191829 points

Hello Zekun,

Thank you.

Regards,

Sreenivasa

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AM3354: How to calculate the temperature of SOC with appropriate RθJC ψJT?