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TMS37157: Need help with harvesting energy from field of TMS37157 transmission

Part Number: TMS37157

Hi gents,

I need you help again with TMS37157.

I designed the following according to swra395.pdf application node (see attached schematics)

The problem is, that the capacitor C11 is not charged to 15.8 V as I expected.

I can delete D3 and supply the DC/DC converter with a lab power supply and the converter works perfect.

But, I can't get it running from the NFC field.

Is this maybe an inrush effect?

Any ideas?

  • Hello Gerd,

    I haven't had any questions about that design come up before so trying to work through who has sufficient background to offer feedback. The team members I'd need to hear from are in Germany so I won't know more until Monday at the very earliest.
  • Hello Gerd,

    The information that C11 isn't charged is not very useful as that could also indicate a problem with the DC/DC converter.

    One thing we need to know is if the VCL that is supplied to the TMS37157 can provide at least 5.75V when the device is in the RF field of a reader.

    A first test that would be good is to remove the D3 diode and measure the voltage when the device is in the field. This could indicate if the DC/DC converter is drawing too much current from the RF field energy, and would explain why the lab power supply offers no issues.

    In general, it sounds to be a power sourcing problem, so the more detailed analysis you can give us for power numbers and comparison between powering via RF field vs powering via lab power supply, the better we'd be able to comment on how to solve the issue.
  • Hello Ralph,

    I'll try to test this as soon as possible.

    Thanks

    Gerd
  • Hello Gerd,

    Have you had the time to run the test? If not, can I close this thread for now? If I do, you can reply within 30 days to re-open or just re-post via Ask a Related Question.