Nexperia USA Inc. 74HC Logic – Buffers, Drivers, Receivers, Transceivers parts available at DigiKey. 74HC Datasheet, 74HC Octal Buffer Datasheet, buy 74HC C. • Balanced Propagation Delay and Transition Times. • Significant Power Reduction Compared to LSTTL. Logic ICs. • HC Types. – 2V to 6V Operation.
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Other than for logic reasons, why would you choose an inverting buffer over a non-inverting one, or vice versa? My routing constraint isn’t the LEDs, and really, it’s not the buffers either ‘ and 74hc5541 have identical pinouts, after all.
As long as you are not violating any spec in the datasheet, go ahead and wire up the LED whatever way is 774hc541 convenient for you. I’ve noticed a tendency for people to use the 74HC instead inverting buffer. This means you want a inversion in there for a logic high to cause the LED to light.
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The total Vdd and Vss currents the device is rated for may also not be symmetric, even if individual pins are. I was just wondering if there’s a good engineering not logistical reason for choosing one over the other, when you can go both ways.
Olin Lathrop k 74nc541 I’m just trying to save on the number of different parts it calls for lots of ‘s, and no ‘s. Sign up or log in Sign up using Google. It looks to me like these permutations are pairwise equivalent. Sign up using Email and Password. Alexios 6 If you intend to run the LED from the same supply as the logic gate, and that gate can source and sink symmetrically, then it doesn’t matter.
74HC SMD | | CMOS High Speed Logic – 74HC/AHC/AC Series | Online shop – Comet Electronics
There are obviously four permutations here: In general, it is more likely that low side drivers have a little less resistance and that the total Vss current rating is a little higher. I’ve gone through the datasheets and 74ch541 ICs can sink or source 25mA per output pin which is fine.
Thanks, that answers my question. Even though a logic gate may be rated for the same source and sink current, it is still possible that the low side driver has a little lower resistance.
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This is why people are used to wiring LEDs between the output and Vdd. Of course if this is all coming from a microcontroller, which it almost always is these days, then digital signal polarity is irrelevant since it can be handled in the firmware either way. Sign up using Facebook.