topic S32K144 VCC short to GND after power on in S32K

S32K144 VCC short to GND after power on

Jimny — Sun, 13 Dec 2020 12:25:21 GMT

Hello,

I designed a minimum system with S32K144, please see the schematic in the attachment. And then I made a pcb and solder the components.

When I power on the board with a DC power source which outputs a 7V voltage to the LDO on the board, an short circuit occured. After some measurement with multi-meter, I found VCC is short to GND. So I take the MCU off the board and there is no short circuit.

It is obvious that the MCU is internally short-circuited. What's wrong with the schematic? How to get rid of the problem? Can anyone help?

Re: S32K144 VCC short to GND after power on

Robin_Shen — Mon, 14 Dec 2020 02:58:16 GMT

Hi ZZD,

I did not find out error in your schematic.
Please check the PCB file and measure the pads on board.
For example:
pin 7\8\9\41 connect to 5VDC
pin 10\40 connect to GND

If you doubt that the MCU is internally short-circuited, you can measure pads of MCU before solder it on PCB board.

Please check if the MCU is place correctly with PCB pads.

I am not quite sure if this MCU has exposed pad (EP) at bottom. If so:
The bottom of the package provides the primary heat removal path, as well as excellent electrical grounding to the PCB through an exposed pad (EP).

Best Regards,
Robin
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Re: S32K144 VCC short to GND after power on

Jimny — Sun, 20 Dec 2020 13:48:57 GMT

Hi Robin,

Thank you for your suggestion.

I have made a new pcb and solely solder the power supply pins of the mcu. I have also put a zener diode at the output of the LDO. It works. There is no short circuit any more. The circuit draws about 20mA with no software flashed.

I will try to program the mcu at the next step.