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SN74LVC74A: 74LVC74 operating voltages

myk dormer
Prodigy 20 points
Part Number: SN74LVC74A
Other Parts Discussed in Thread: SN74AHC74, , SN74LVC1G74

I am a little confused.
I am looking for a (very) fast D type (clocking at over 170MHz) which will operate from a +5v rail

74LVC1G74 (or 2G74) look ideal (5v rail, >170MHz)

Now imagine I want two of them in a SOIC14
74LVC74 ? …  But no, this part specifies a maximum Vcc of 3.6v even though the absolute maximum Vcc is quoted as 6.5v

So the question is: Can I run a 74LVC74 from a 5v rail, and if not: why not (when other LVC family bistables can)

  • 0
    TI__Mastermind 44665 points
    Hi Myk,

    It is not recommended to operate near the abs max ratings, but it doesn't mean you can't have a 5V supply. However, exposure to absolute-maximum-rated conditions for extended periods may affect device reliability and we can't guarantee proper operation. I would also consider the SN74AHC74.
  • 0 in reply to Dylan Hubbard
    Prodigy 20 points
    The suggested AHC part is capable of clocking at barely half the speed I require (and mentioned in the original question), so is not any kind of viable replacement ...

    Unfortunately my confusion remains:
    SN74LVC74A 3.6v part Absolute maximum 6.5v
    SN74LVC1G74 5.5v part " " 6.5v

    Two parts, performing the same function, in the same LVC family
    They have the same absolute maximum Vcc, but one can safely operate to 5.5v, and the other cannot
  • 0 in reply to myk dormer
    TI__Guru* 96862 points
    Hi Myk,
    The LVC and LVC1G families are a bit different. LVC parts were designed to fulfill the traditional 5V functions from the HC family while operating primarily at 3.3V, while the LVC1G parts were designed to fill a niche application -- where someone might need a single logic gate to fulfill some function. Since these were filling a gap in our portfolio, they were designed and characterized to operate from 1.8V to 5V, preventing the need for an additional family just to support 5V operation.

    You can definitely operate an SN74LVC74A at 5V, however the device was not characterized for that operation, and TI can't guarantee any specs while operating at that supply value.