1
\$\begingroup\$

I am designing a board with a FT230 USB to UART IC. In battery powered applications, one of its GPIO can serve as a VBUS sensing pin.

However, the FT230X was designed for 5V applications, before the era of USB Power Delivery. In my case I'm expecting voltages of up to 20V on VBUS, but with a VIH of 2.0V on the GPIO, I don't see any voltage divider that would produce a logic high voltage on the entire 5-20V range.

So I'm looking for a small circuit that would produce a logic high whenever the VBUS is above 4.5V, as illustrated below.

enter image description here

\$\endgroup\$
10
  • 2
    \$\begingroup\$ Use a comparator. \$\endgroup\$
    – Andy aka
    Feb 25, 2021 at 11:40
  • 2
    \$\begingroup\$ Are you sure the FT230X will do power delivery negotiation for you? \$\endgroup\$
    – Jeroen3
    Feb 25, 2021 at 11:41
  • 1
    \$\begingroup\$ You don't need a high voltage comparator. Make a voltage compare with the potted down voltage and run the comparator from 5 volts. \$\endgroup\$
    – Andy aka
    Feb 25, 2021 at 14:21
  • 1
    \$\begingroup\$ also you can use a resistor+zener to clamp down to something manageable (like 6 volt) and work from that. Or even use a zener to subtract the 5V, depending on the precision you need \$\endgroup\$
    – Lorenzo Marcantonio
    Feb 25, 2021 at 15:50
  • 1
    \$\begingroup\$ @ymakux I believe I never finished this design, so no definitive answer. I didn't like the approach of the zener diode as it would dissipate power unnecessarily. I still think I would purse the option of using a comparator. \$\endgroup\$
    – nschurando
    Mar 21 at 19:58

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.