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The features clause in the datasheet (https://www.microchip.com/en-us/product/atf16lv8c) specifically mentions "Inputs are 5V Tolerant",

but the DC characteristics specify VIH to be MAX Vcc+1

It's unclear whether I can power this chip using 3.3V and still be 5V input tolerant. I would guess that if it really was 5V tolerant, the max VIH would have been 5V.

Or is there something basic I don't understand.

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the DC characteristics "input high voltage" is the voltage range at which an input counts as "high".

The fact that the device doesn't get inherently damaged at some input voltage doesn't mean it can reliably function at that.

Would seem like you could use the input at 5V if you add a series resistor large enough to avoid any protection diode conducting too much current; seeing that safe input leakage is specified at 10 µA, I'd guess that implies that at R= (5.0 - 3.3)V/(10 µA), you'd be safe. But honestly, that's a good question to ask atmel/microchip support!

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  • \$\begingroup\$ But if the voltage range has a minimum of 2.4V and max of Vcc+1, and I power it with 3.3V, that would mean that I cannot use a 5V signal as a high input. So it's 5V tolerant as to not get damaged, but not in a useful way other than that? \$\endgroup\$
    – Photon
    Commented yesterday
  • \$\begingroup\$ maybe, at least the datasheet doesn't say so. \$\endgroup\$
    – Marcus Müller
    Commented yesterday
  • \$\begingroup\$ @Photon If you need VOH from your peripheral device to be lower for the MCU's VIH, you'll need a voltage level translator/shifter. I assume you're trying to build a UART line from your MCU to another computing device? \$\endgroup\$
    – Colin
    Commented yesterday
  • \$\begingroup\$ @Colin I'm trying to build a retro pc (which is all 5V) and a 3.3V mcu as the IO controller. I'm trying to avoid level shifters by using LVC latches and PLDs. The latches do exactly what I need, inputting 5V and outputing 3.3V, but it seems that I don't have a similar solution for the PLD. \$\endgroup\$
    – Photon
    Commented 22 hours ago

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