TPS61028: VBAT / GND Short

Prodigy 50 points

Part Number: TPS61028

Hi,

We experience the problem that the TPS61028 fails under unknown circumstances.

What happens is the part develops a short between VBAT and GND,

The layout is as recommended in the datasheet
Instead of a tantalum C we use a ceramic C plus series resistor
On the input side we never observe any voltages greater than 5.5V
The component is not exposed to hot environment
In our lab we cannot reproduce the fault (e.g. with excessive input voltage, noise, short on output, ...)
We use EN to infrequently start/stop the converter
We boost from Li-Ion cell to 4.2V
We operate the part in continuous mode (i.e. PS pulled high)

Any help is greatly appreciated

Matthias

over 5 years ago

0 Jasper Li over 5 years ago

TI__Mastermind 46905 points

Hi MH,
do you remove the inductor when you measure the impedance between the VBAT and GND. if not, please remove the inductor and double check if the short in between VBAT and GND or SW and GND.

0 Armin Felber over 5 years ago in reply to Jasper Li

Prodigy 20 points

Short is between SW and PGND

0 MH over 5 years ago in reply to Jasper Li

Prodigy 50 points

Hi Jasper,

The short is between SW and PGND. The impedance tends to be around 4R.

Thank you

0 Jasper Li over 5 years ago in reply to MH

TI__Mastermind 46905 points

Hi MH,
could you share me the layout and the schematic? the SW to GND short is normally caused by the voltage spike in SW pin. the voltage spike level is related to the layout.

0 Armin Felber over 5 years ago in reply to Jasper Li

Prodigy 20 points

The layout is quite close to the recommended one and has been reviewed by TI as far as I know (not sure) and should be ok. Spikes on the SW pin can go as high as app. 7.5 V. Measured with shortest possible lead to ground (no normal ground lead)

No ringing, just a small peak.

Regards

AFE

0 Minqiu Xie over 5 years ago in reply to Armin Felber

TI__Mastermind 21565 points

Hi AFE, M:
The absolute maximum ratings for the SW PIN is 7V max. And the layout and waveform are important for us to find the risks. You could share the materials with private message if the forum is not convinced for you.

*Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

0 Minqiu Xie over 5 years ago in reply to Minqiu Xie

TI__Mastermind 21565 points

Hi AFE, M:
I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out)
Thank you~

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TPS61028: VBAT / GND Short