MM912G634DV1AE hot and smoking

[daviddai]

Hi,

I try to debug my source coade with Code Warrior IDE 5.9.0 and P&E USB BDM Multilink,

but always failed to connect with MM912G634DV1AE, then I found MM912G634DV1AE is very hot.

Firstly, I doubt the Multilink or my schematic have some issue.

But lastly, I simplify  my schematic as below, then power on with no connection to Multilink,

MM912G634DV1AE is also very hot, the current is greater than 100mA,(BTW, I test this schematic with at least 3 pcs MM912G634DV1AE, result is same).

Could you please tell me the reason? My understanding is the MM912G634DV1AE should enter sleep mode as below schematic.

Thanks a lot!

Best Regards

David Dai

[iggi · Accepted solution]

Your simplified schematic does not look good. There shouldn't be capacitor on /RESET pin.

The VDDX supply pin should be connected to 5V and decoupled.

I doubt there is a problem with the devices, all three (i hope you have got them from authorized distributor).

Not sure if they are burned/damaged. We have got similar problem with an another device S12UB which gt burned due to ESD and each time we connected power supply, it become hot a lot.

Here is the part of schematic of the KIT912H634EVME board, so you can use that as a reference:

[daviddai]

Hi iggi,

Thanks for your response.

The simplified schematic is just used to verify the MM912G634DV1AE will be hot or not.

The fully circuit is as below:

As you said the possible reason is ESD,

Actually I purchased the MM912G634DV1AE from Freescale offical website,

I already tested almost 10pcs MM912G634DV1AE, but no one can communicate with BDM Multilink,

I confused, could you please tell me the possible root cause?

Thanks a lot!

Best Regards

David Dai

[RadekS]

Hi David,

MM912H634 contains analog and MCU dies.

We have to ensure that analog die will not interrupt our communication by watchdog reset.

Therefore we have to connect at least 8V at TCLK pin for disabling watchdog at analog die.

As I see on your schematic, you connected TCLK directly to GND. This will leads to situation when watchdog at analog die resets MCU prior you finish programming. I would like to recommend pull-down between TCLK pins and GND and test point at TCLK pin. In this case, you can temporary disable analog die watchdog during programming by connecting to at least 8V.

Other option is jumper solution as on evaluation board.

I hope it hleps you.

Have a great day,
RadekS

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[daviddai]

Hello RadekS,

Thanks for your response,

Regarding the MCU is hot, I think Mr iggi is right,

I solder the demo board by myself hand, it's not a good way.

Everything is ok after I used SMT machine.

Regarding the communication issue,

actually I already tried to connect TCLK pin to 12V,

but I can't connect MCU to Multilink else.

Then I keep TCLK pin to GND, and just disconnect REST and REST_A, then connect REST pin to Mulitilink BDM connector pin 4 directly, everything is ok.

Could you tell me the reason? Thanks!

Best Regards

David Dai

[RadekS]

Hi David,

The reason is clear - analog die resets MCU.

Most probably reason for reset from analog die side is watchdog event.

According MM912G634 reference manual:

For debug purpose, the watchdog can be completely disabled by applying VTST to the TCLK pin while TEST_A is grounded. The watchdog will be disabled as long as VTST is present.

I would like to apologize, but I forget check range of VTST. For disabling analog die watchdog is necessary attach voltage in range 7-10V. My recommendation about at least 8V was not correct. I am sorry. Since 10V is absolute maximum voltage for TCLK pin, I hope that my advice didn’t cause any new damage at analog die side.

I hope it helps you.

Have a great day,
RadekS

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[daviddai]

Hello RadekS,

Ok, thank you.

At my new debug board, I already connected the TCLK to GND,

so no damage to MCU.

Thanks!

Best Regards

David Dai