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LS, C, HC series — Parallax Forums

LS, C, HC series

Vega256Vega256 Posts: 197
edited 2012-12-14 21:49 in General Discussion
Hey,

I'm drawing up a schematic in ExpressPCB, and in my actual project, I have Low-power Schottky, CMOS, and High-speed CMOS series logic chips. I probably shouldn't have mixed types, but they're what I can get to right now.

In ExpressPCB's component library, there are only components for the LS series. As one would expect, I don't think that creating custom parts for each series of the logic chips is efficient. Are the LS, C, and HC series all pin compatible with each other? If so, I could just use the components for the LS series.

Comments

  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-12-14 15:16
    They should be; I've never seen any examples to the contrary.

    If I were you, I'd look up specific datasheets for the parts you're using, just to make sure, but I imagine you're just fine.
  • Vega256Vega256 Posts: 197
    edited 2012-12-14 15:43
    Thanks. This should save some time.
    Circuitsoft wrote: »
    If I were you, I'd look up specific datasheets for the parts you're using, just to make sure, but I imagine you're just fine.
    Good idea...
  • evanhevanh Posts: 16,109
    edited 2012-12-14 16:55
    Functionally they're the same, but they have differing electrical characteristics, which means you shouldn't just mix them together willy nilly.

    LS is rated for 4.5 volts to 5.5 volts supply, a threshold of 0.5 volts, and typically a drive current for ten LS inputs. Similar for AS, S, F, ALS ...
    HC is rated for 2.0 volts to 6.0 volts supply, a threshold of 50% of supply voltage, and typically a drive current for ten HC inputs. Similar for AC, BC ...
    C is somewhat orphaned, it's electrically identical to the 4k series, it is rated for 3.0 volts to 15.0 volts supply, a threshold of 50% of supply voltage, and typically a drive current for ten C inputs.

    Then you get the HCT and ACT variants that have HC drives but with 0.5 volt thresholds. And further there is the low voltage variants that explicitly target the 1 volt to 3 volt supply ranges.
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-12-14 21:28
    Vega;
    Vega256 wrote: »
    Are the LS, C, and HC series all pin compatible with each other? If so, I could just use the components for the LS series.
    The simple answer is "mostly" but not all. Yes, there were some LS parts with odd pinouts.
    I always check each one.

    Duane J
  • jmgjmg Posts: 15,183
    edited 2012-12-14 21:49
    Vega256 wrote: »
    Hey,

    I'm drawing up a schematic in ExpressPCB, and in my actual project, I have Low-power Schottky, CMOS, and High-speed CMOS series logic chips. I probably shouldn't have mixed types, but they're what I can get to right now.

    In ExpressPCB's component library, there are only components for the LS series. As one would expect, I don't think that creating custom parts for each series of the logic chips is efficient. Are the LS, C, and HC series all pin compatible with each other? If so, I could just use the components for the LS series.

    I'm not quite following, is this question for schematic symbols, or real. physical parts ?

    Generally, parts with the same derivative part number are 100% pin-compatible - but this is quickly checked on the net.

    On Symbols, it is common to have Generic TTL library parts, that are placed and tagged with a specific part number.

    So a /04 symbol, could be labeled as any of HC04/HCT04/HCU04/AHC04/LVC04/VHC04/LVX04/LV04 .....

    If you are talking about mixing physical parts, 'C' parts tend to be low drive, and may struggle into a LSxx device
    - eg you will see data tags like this
    Fan out of 2 driving 74L
    - best to simply bin the dinosaur parts, and get at least HC, as then you can cover 3V and 5V.
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