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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

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    \$\begingroup\$ Use a comparator. \$\endgroup\$ – Andy aka Feb 25 at 11:40
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    \$\begingroup\$ Are you sure the FT230X will do power delivery negotiation for you? \$\endgroup\$ – Jeroen3 Feb 25 at 11:41
  • \$\begingroup\$ I'm expecting voltages of up to 20V on VBUS I'm not since the FT230 doesn't support that and cannot do the PD negotiation to request more than 5 V from the USB host so the USB host will never deliver more than 5 V. This is exactly why the negotiation is needed, to prevent the USB host from providing more than 5 V to devices that cannot support it. See it as a "secret handshake", only if you know it, you get 20 V. The FT230 doesn't know the secret handshake. \$\endgroup\$ – Bimpelrekkie Feb 25 at 12:01
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    \$\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 at 14:21
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    \$\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 at 15:50

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