Quiescent Current of FS32K144HFT0VLHR increase when Temperature Decreases

[AmyJiang]

Schematic diagram as shown below.

Test the quiescent current of MCU(FS32K144HFT0VLHR) at VLPS mode when VDD=5VDC.

The consumption current would increase as the ambient temperature decreasing.

Why does consumption current increase with ambient temperature decreasing?

[davidtosenovjan]

Specifically you have there signals marked as KL..

Isn’t possible their level is between Vih_min and Vil_max? It could increase current consumption because of toggling input between logic 1 and logic 0.

[AmyJiang]

Hello

I have removed the other modules (DC-DC power module, CAN Transceiver, etc.), only the MCU chip and its peripheral devices left with 5V power supply. SO there is no current injection on PTA7.

Thanks a lot!

Regards,

Amy

[davidtosenovjan]

It is incorrect interpretation of injection current. Injection current flows over internal clamping diodes in case that pin input voltage is higher that power supply voltage VDD (or input voltage is lower than VSS), it is „not wanted“ current. Maximum output currents (given by drive strength) are operating currents (i.e. “wanted“).

Following appnote is dealing with injection current in the great detail:
https://www.nxp.com/docs/en/application-note/AN4731.pdf

What you could possibly facing is switching current (current consumption over VDD power rail) due to unterminated Hi-Z input or if there is input with level somewhere in the grey zone (between Vih_min and Vil_max).

[AmyJiang]

I learned that. Thank you!

[davidtosenovjan]

Hi, it is very unusual because typically lowest consumption comes with lowest temperature and highest consumption with highest temperature.

I have seen you are dealing the same topic with my colleague over case. I would agree it could be related to external I/O connection.

Have you tried different MCU piece? Does it behave the same way?

[AmyJiang]

I have tried different MCU pieces, and they behave the same way.