TPS62867: What happens when 2.2uH inductor is used instead of 0.22uH?!

Part Number: TPS62867

Tool/software:

We use four TPS62867RQYR on one of our boards to generate the following 4 voltages:

  • 0.95V
  • 1.2V
  • 1.8V
  • 3.3V

from the common 4.2V input voltage. All 4 instances show the correct 220nH inductor on the schematic:

However, the BOM has by mistake listed a 2.2uH inductor, more specifically the DFE322520F-2R2M=P2 (3.3A, 0.04 Ohm). Do you see an issue with it in the situation where the consumption current does not exceed 2.5A?

From what we can see, the buck and board function properly, and we wonder whether it makes sense to go through the trouble of changing the inductor to the value specified in the datasheet, specifically to the 240nH DFE201612E-R24M=P2 (5A, 0.02 Ohm).

Could you please provide your expert advice on what may go wrong, if anything, as a consequence of this BOM mistake?

  • Hello,

    thanks for reaching out in E2E.

    The IC's loop compensation is optimized for the recommended L-C combinations for the output filter. Other values can lead to instability. Also the desired efficiency- and load transient performance might not be met.

    I would suggest to follow the datasheet recommendation for the inductor.

    Best regards,

    Andreas.

  • Thank you for these insights.
      - Are we saying that that beefing up the C may also lead to instability?

    What we typically find is that the C follows the datasheet on the schematic page where the buck is instantiated. But, the C freely builds up on all other pages where the corresponding supply rail is used.