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| gaminn:
Hi, I have two boolean expressions: Y1 = A Y2 = (not A) and B I have to select cheapest solution to realize this on my PCB (cheapest IC, only one IC prefered). Can you please give me an advise? A and B are slowly changing signals so it will be great if the input gates have schmitt trigger. Vcc = 5 V. Switching speed is not important. |
| magic:
They should be making 4x2bit PROMs in SOT23-6 for that kind of thing. Also 8x3bit in DIP8/SO8 if we are at that. You know, you can always use some SOT23 µC :popcorn: edit Alternatively, if PCB space isn't critical, a hex inverter with Schmitt-triggered inputs like 74HC14 could be used for input denoising and output drive plus two external diodes to implement AND. |
| mikerj:
A 74HC132 costs pennies and gives you four 2 input NAND gates with schmitt triggers. Two of these gates wired as inverters in series will give you /A and Y1. Feed /A and B into another gate, the output is /Y2. Use the final gate wired as an inverter to get Y2. |
| zzattack:
Well Y1 is simple, seems a copper trace will do. For Y2 = (not A) and B you can try rewriting it to a combination or NAND or NOR gates and pick a 7400 ic. Use the ideas that (not X) == (x nand x), not (x and y) == x nand y, and rewrite your expression by replacing all logical operators by their equivalent using only NAND operators. I.e., --- Code: ---1. Y2 = (not A) and B == 2. (A nand A) and B == 3. not not ( (A nand A) and B) ) == 4. not ( (A nand A) nand B) == 5. ( (A nand A) nand B) nand ( (A nand A) nand B) --- End code --- So a single 7400 would work. Equivalent using NOR gates is also possible, and mux ic's can very often be used just the same. |
| gaminn:
Thanks for your advises guys. I also came accross these multi-gate (configurable) ICs: 74LVC1G58 and similar. I will probably use them. Two of them do what I need. |
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