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TPD2E001 in a bus-powered device with a Li-Po battery

Jan Rychter
Intellectual 305 points
Other Parts Discussed in Thread: TPD2E001

I'm designing a device that has a LiPo battery and a USB connector. USB is used for charging and communication. The on-board microcontroller is powered from either the battery or USB via an integrated 3.3V LDO. 5V is present on board (via a boost converter), but only intermittently.

I am not sure on how to best connect the VCC pin of the TPD2E001. Connecting it to 3.3V makes no sense, 5V isn't always present, so I can either connect it to VBUS or leave open. But connecting it to VBUS of the USB connector means the device won't be protected against surges on VBUS, right?

  • 0
    TI__Genius 12190 points

    Jan,

    A Vcc of 3.3V is fine as long as your signal on the io pins does not swing above Vcc + Vf_min = 3.3V + 0.65V = 3.95V. Don't forget the 0.1 micro-farad capacitor on Vcc pin. This will protect the VBUS per data sheet.

    Regards,

  • 0 in reply to Guy Yater
    Intellectual 305 points

    I thought USB signals could swing to 5V, which is why I wrote that connecting it to 3.3V made no sense. But now I checked and indeed "Transmitted signal levels are 0.0 to 0.3 volts for low and 2.8 to 3.6 volts for high in full-bandwidth and low-bandwidth modes".

    This means that I can connect Vcc to my 3.3V supply. And I did place the capacitor.

    Thanks!

    --J.