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TPS54418: Ripples caused by poor PowerPad-to-GND connection?

Part Number: TPS54418

Dear Team,

one of our customers recently discovered a problem with the TPS54418. Some boards are showing a higher ripple of 300mV on the output. (edit: The issues are seen at start-up and/or when using a cooling spray. So when having cold temperature conditions).

Further investigations and a x-ray showed that the GND pad was having a poor connection (~50%).

In the data sheet I saw that the pad is in the function of being a thermal pad only, see page 12 / section 8.2:

May I ask you to comment if the PowerPad also has an influence on the part's control loop?

Thanks and best regards
Martin

  • The IC substrate is connected to the thermal pad with a thermal bonding compound. The electrical conductivity is not specified, but generally it is very low and the thermal pad can be considered as "GND". Do you have waveforms the demonstrate good and bad performance? can you post the schematics and layout? If you do not want to post them here, please contact me directly.