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TPS55165-Q1: Inductor DCR requirement

Nicolas M
Prodigy 10 points
Part Number: TPS55165-Q1

Hi,

I'm designing a buck-boost converter and in the datasheet (https://www.ti.com/lit/ds/symlink/tps55165-q1.pdf?HQS=dis-mous-null-mousermode-dsf-pf-null-wwe&DCM=yes&ref_url=https%3A%2F%2Fwww.mouser.es%2F&distId=26) I have seen that a maximum DCR is stated for the inductor in section 7.5. A maximum of 40mOhm is stated as the requirement.

The inductor I'm planning on using has a higher DCR of 120mOhm. However the load has a fairly high resistance, around 60Ohm, resulting in a ratio between Rl and DCR of 500. The output voltage is 12V, in case that matters.

Could you provide any information on why is there a DCR requirement in the datasheet? What are the expected consequences to not following this requirement?

Thanks and regards.

Nicolás.

  • 0
    TI__Guru* 78200 points

    Hi Nicloas,

    Thank you for considering the TPS55165-Q1.  Our experts are currently on national holidays and they can comment after Oct 7th.  What I can tell now is that those limitations on the external component selection are required by the internal loop compensation circuit .   Beyond the limitations in component selection would lead to instability issue.  

    Best Regards,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 10 points

    Hi Youhao,

    Thanks for your answer. Hopefully your experts can provide some more information on the impact of the DCR in the compensator.

    Regards

  • 0 in reply to Nicolas M
    TI__Mastermind 34231 points

    Hi Nicolas,

    The inductor DCR will cause higher power loss, so the buck-boost converter efficiency would be lower than expected and maximum output current capability would be affected.