SN74LVC8T245: Bus Hold

high speed guy

Part Number: SN74LVC8T245

Hi,

Since this LVC technology based device has bus hold feature do we need to still be concern about inputs that are left floating? Can a condition occur if left floating that will result in potential damage to the part? If so what are the general conditions to guard against ? The Application Report SCBA004D–July 1994–Revised September 2016 Implications of Slow or Floating CMOS Inputs implies there are protections with the bus hold circuit however it is not clear if this protects for all scenarios.

Thank you,

HSG

over 2 years ago

0 Rami Mooti1 over 2 years ago

TI__Mastermind 23553 points

Hey HSG,

Not all LVC devices have the bus hold feature. The ones that do will be denotes with the H in the name; eg SN74LVCH8T245.
For the SN74LVC8T245 you would need to tie these to GND.

[FAQ] How does a slow or floating input affect a CMOS device?

If this was simply a typo and you intended to ask about the LVCH family, then there isn't a need to pull these high or low.

From the datasheet :
"Active bus-hold circuitry holds unused or undriven inputs at a valid logic state. Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended."

Hope this helps!
Rami

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SN74LVC8T245: Bus Hold