TPS63061: Fault - no output voltage and death of TPS63061

Hi Holger,

Thank you for reaching out.

Could you please give us more details about the failed devices:

1. Did the failed devices never manage to start, or did they failed after some time operating under certain (which?) conditions?
2. Can you please share your PCB layout? If this is sensitive you can send it to me in a private message.

Best regards,
Milos

Hi Milos,

thank you for fast reply.

1. The faulty devices work well for a few month. Most of them has no Problem any time. But some are faulty. At some ICs you can see a "blowhole" on the housing

The detailed condition at the time of failure is unclear. The Input voltage is normally 4,8V (battery Operation 4x1,2 NiMH) or operation with a external power supply with 9,0V.

2. PCB Layout:

Best regards,

         Holger

Hi Holger,

Thank you for the additional info. It is difficult to pinpoint the problem since the device worked for some time before failing. My guess would be either overvoltage or overtemperature induced failure. 

I overlooked that on the schematic you have only around 2 μF on the input side. We recommend at least 20 μF. It is important to have enough capacitance to support switching pulses, and it also helps for point 1 below. 

1. How far is the input power supply (the batteries or the external 9 V) for the TPS63061? If the device turns off due to overtemperature, it could create a voltage spike due to parasitic inductance on the input side if the line from the batteries to the TPS63061 is long. If the input supply is located more than 10 cm from the TPS63060, additional bulk capacitance should be added, for example a 47-100 μF electrolytic/tantalum capacitor.
2. Can you please show us the photo of one of the blown devices so we can see which part might have failed internally?
3. Is there a GND plane that is not shown in the above image? In general, the layout looks good, but if the device operates at high output currents, there should be more GND vias close to the device PGND pins and close to the GND ends of input/output capacitors. Please refer to the recommended PCB design below.
4. Is there anything else connected to the input side of the TPS63061 that could be a source of voltage spikes?

Best regards,
Milos

Hi Milos,

thank you for the detailed statement. 

1. the Input power supply is ~5cm far away from the device. There is a curcuit with fuse, inverse polarity protection, filters, capacitors (as well 220uF), 

2. please find here a picture of a damaged TPS63061. Other faulty units have no visible damage.

3. All Vias are connect to the GND plane layer. (complete plane of PCB)

4. The power supply circuit from 9V input and batterie a connected to the U2 voltage. In Addition there is parallel a second power supply device for 3,3V (MCP1703T).

Do you have any concluding recommendation ? If it is helpfull, i can send you the complete part from the power supply of the schematic to your private address.

How  can a send a private message ?

Best regards,

    Holger

Hi Holger,

The damage occurs where the buck stage is. I assume this is an overvoltage, and would like to see the schematic of the power part if possible. You can send me the files in a private message after you accept my friend request.

Best regards,
Milos