Questions about TMU Sensor Placement, Junction Temperature, and TDP for i.MX 8M Plus

[jhan_ktcp]

Hello,

I'm studying on thermal management using the i.MX 8M Plus processor, and I'm trying to determine appropriate cooling strategies. I've reviewed the Reference Manual and Datasheet, but there are still some unclear points I'd like to ask about.

I'm specifically trying to estimate or compare the junction temperature, but it's not clear where the internal TMU temperature sensors (labeled "SoC" and "CPU" in Linux) are physically located. Could you clarify:

Q1. Where exactly are the "CPU" and "SoC" TMU probes placed within the die?

Q2. What is the difference between them in terms of which parts of the chip they represent?

Q3. Since the CPU processor has 4 cores, is the CPU probe placed near the center of the cluster, or does it focus on a particular core?

Q4. Also, the reported temperatures for SoC and CPU are often different — how are each of these values related to the actual junction temperature?

Q5. In addition, I’d like to ask whether there is any official information available on the TDP (Thermal Design Power) of the i.MX 8M Plus — either typical or maximum — or at least a specified maximum case temperature that can be used for thermal modeling and simulation.

Thank you in advance for your support.

[JorgeCas]

Hello,

Q1. There is no information where are these probes physically in the processor.

Q2. "CPU" represents the temperature of Cortex-A cores, near to CPU cluster and "SoC" represents the overall temperature of the SoC, including the DDR controller, GPU, VPU, NPU and peripherals.

Q3. It is placed near the center of the cluster.

Q4. "CPU" is a more representative junction temperature since represents the temperature according to the processor load and "SoC" represents an overall temperature of the system.

Q5. Thermal model can be requested under NDA (.pdml).

Best regards.