AND gate with a latch/saving function?

Hey @DigiKey_Internal! My coffee isn’t working this morning and I could use another pair of eyes to make sure I’m understanding this request correctly.

Customer writes:

Hello, I need a AND Gate IC but with a saving function. For example:
Signal A&B go into the input A&B of the IC meeting the AND requirement which releases signal C.
Usually if then one or both of the input signals go away the true status turns into false and the C output signal stops but I need it to continue.
I need the IC to omit the C output signal until the IC has gone from true→false→true again.
I hope that makes sense haha. Any recommendations?
False (idle state of the IC. Not outputting the C signal) →TRUE (the IC is omitting the C signal)→ FALSE (The IC is still omitting the signal)→TRUE (IC has stopped omitting the C signal)→FALSE ( IC is idle. Not omitting the C signal until TRUE)

To me, it sounds like an AND gate with a latch and I would imagine this would be in our Logic - Gates and Inverters - Multi-Function, Configurable category. But I see no such option for an AND/latch option. Is there another terminology or single-chip solution?

(Side note, this is a public post on TechForum)


For single chip solution I’d use a 6 pin, 4 I/O, micro-controller like this PIC10 series part:
This assumes a build < 1,000 pieces and nickels and dimes not being an obstacle.

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I’ll pass that suggestion over to the customer.

Another idea I came up with is to create a latch with a couple NOR gates and have it feed into the AND gate. This would be if he wanted to stick with the gate technology.

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The description implies quite a few logic gates to accomplish. One might have been able to get by with an AND gate and a FLIP-FLOP, except for the requirement that it output TRUE on the initial case of the AND gate inputs being TRUE. As you state, it also implies a possible requirement for a synchronous latch. Because of that, it gets more complex.

If they don’t require logic gate type speeds (low nanosecond speeds, then Paul has the right idea. This is a trivial task for any small MCU and can switch at a few microsecond rate or faster, depending on the specific MCU chosen.

If they need logic gate type speeds (<100ns), then they either need several logic chips (not sure which ones off hand), an SPLD, or a CPLD. Based on the terminology used in the description given to you, those are probably outside the scope of what they would be expected to be able to use. Chances are they do not need this speed, so the MCU makes the most sense. Sounds like a job for one of the “x-UINO” products or similar.

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