STSPIN32F0 damaged on custom board and need solution to avoid another

[x4ce]

Hello,

I have developed a custom BLDC Motor Controller board using STSPIN32F0. During the testing of board, it was observed that its built-in DC/DC Buck Converter was not producing 3V3. After going through AN5128, I found a mistake that other side of SW's inductor was not connected to VDDA (this VDDA is also connected with VDD). So, I shorted these two points as shown in below figure during the board was powered on. I tiny spark was on the capacitor where I placed a jumper wire but it was found that VDD and GND have been permanently shorted. I removed all the VDD to GND caps to clear the fault which was eventually cleared on removing the STSPIN32F0.

Now, I have only one spare STSPIN32F0 and I don't want to brick. I have following queries if someone could answer:

1. According to following figure, I need to connect above short which led to bricking STSPIN32F0. If, so, STSPIN32F0 was damaged due to making that short when device was already powered on and may be giving full VM voltage? I can make a permanent short on this and then power on STSPIN32F0?
2. 

    For the moment and testing purpose on the spare STSPIN32F0, can I leave this as it is and supply VDD externally? Leave this SW floating and connect VDD/VDDA externally as given below in the datasheet?

I will be grateful, if someone could guide in above queries as I have only one spare STSPIN32F0 and can't take any further risk.

Thank you for cooperation.

Regards

[Richard Li]

1. I think your guess is right, damaged because "hot plug", but one more possibility is, the VM too low - 5V, VM Vmin is ~ 8V, so your circuit VM turn off,(under UVLO) it is lower than VDD.

2. You can use external 3.3V , but need one more >8V power for VM.

[x4ce]

Thanks for your response.

I have replaced the STSPIN32F0 but it is not connecting with the STM Programmer. May be that impulse has damaged PCB as well. When supply power (12V), initially, current is stable around zero then after few seconds starts shooting. May be there are other caps damaged as well.I will look into it or may replace PCB.

[Richard Li]

If you want use external 3.3V, you have to disconnect SW node, the SW still keep on/off.

You said after few seconds, maybe you keep SW node with external 3.3V, it will damage inside logic.

[x4ce]

I had SW node floating and even removing STSPIN32F0 there was same current behavior. May be the Low & High Sides were floating due to chip removal and they are drawing current. I have started assembling another PCB at the moment and I am able to communicate with STSPIN32F0 but not previous board the same was not communicating. So, there must be some damage in either PCB or decoupling caps however the voltage was 3.3V across these caps.