> Hi guys,
>    Any chance of a quick sanity-check?
>
> 74LVC07A: http://focus.ti.com/docs/prod/folders/print/sn74lvc07a.html
> 74LVC14A: http://focus.ti.com/docs/prod/folders/print/sn74lvc14a.html
>
>    The datasheet for these specifies a Vcc of 0V to 3.6V (for the LVC14)
> and 0V to 5V for the LVC07. Input voltage is specified as 0V to 5.5V
> regardless of Vcc voltage -- even the LVC14 can apparently take a 5V
> input, despite its Vcc being limited to 3.3V or less.
>
>    Somehow this doesn't seem right -- these are CMOS parts (LVC = Low
> Voltage CMOS), so surely there are parasitic diodes to Vcc and Vss,
> which would prevent any input from being driven above Vcc without the
> chip latching up?
>
>    Am I missing some critical point here?

No this is correct. Even the PIC F33 series can accept 5V inputs into the
3.3V part. The LVC07 is an open collector part, so can drive a 5V device
as long as it is pulled up to 5V. be careful of the pullup resistor size,
there is a limit to the amount of current it can sink. The PIC F33, for
example, can only sink or source 4Ma max from a pin.

--Bob A


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