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Latching power switch chip?

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mkr5000

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Jan 30, 2023, 11:38:00 AM1/30/23
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Is there a simple all in one device that serves as a latching power on/off for use with a momentary switch? I know I can do something with discrete transistors but wondering if there is something now that's in a single package? (with zero current draw when off) -- thanks

mkr5000

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Jan 30, 2023, 12:19:07 PM1/30/23
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On Monday, January 30, 2023 at 11:38:00 AM UTC-5, mkr5000 wrote:
> Is there a simple all in one device that serves as a latching power on/off for use with a momentary switch? I know I can do something with discrete transistors but wondering if there is something now that's in a single package? (with zero current draw when off) -- thanks
and low current also -- 250ma at most.

Ricky

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Jan 30, 2023, 12:24:56 PM1/30/23
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Sure. A D input FF can have the D input tied to the Q- output and will change state on each toggle on the clock line. You will need to do something to debounce the signal from a momentary switch. That circuit can be more complex than a transistor based On/Off control. Many of the On/Off controls are inherently debounced. You can get a pair of P/N channel FETs in a single package. That's pretty close to a "chip". Add a few passives and you are done.

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Rick C.

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Ricky

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Jan 30, 2023, 12:34:09 PM1/30/23
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On Monday, January 30, 2023 at 1:19:07 PM UTC-4, mkr5000 wrote:
Ok, here's one that is actually a chip. No passives required. It's not zero power though, just close to it. If it is not allowed to draw any power when off, you will need to make is from mechanical parts. They make push buttons that do this.

https://www.analog.com/media/en/technical-documentation/data-sheets/MAX16054.pdf

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Ed Lee

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Jan 30, 2023, 12:35:41 PM1/30/23
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https://en.wikipedia.org/wiki/Triac ?

Fred Bloggs

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Jan 30, 2023, 12:52:59 PM1/30/23
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On Monday, January 30, 2023 at 11:38:00 AM UTC-5, mkr5000 wrote:
> Is there a simple all in one device that serves as a latching power on/off for use with a momentary switch? I know I can do something with discrete transistors but wondering if there is something now that's in a single package? (with zero current draw when off) -- thanks

https://www.adafruit.com/?q=latching+switch&sort=BestMatch

Anthony William Sloman

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Jan 30, 2023, 10:12:16 PM1/30/23
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A latching reed switch would do the job. They take about a millsecond to switch the reed contact from open to closed, or back again.

It would pay to keep the power on for a bit longer - reeds have a nasty habit of bouncing after they first close - but that's trivial to organise.

https://www.asia-manufacturer.com/manufacturers/001/products-detail_38626_100076754.html

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Bill Sloman, Sydney

Fred Bloggs

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Jan 31, 2023, 9:33:28 AM1/31/23
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Well, from what I can see, they're calling push-on/push-off switches "latching" switches these days. It's a mechanical latch, some kind of tang. Looks like the manufacturers of pushbutton switch lines most of the time have this latching version in that line, even those little PCB mounted "microswitches"- and of course tons of panel mounts.

>
> --
> Bill Sloman, Sydney

mkr5000

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Jan 31, 2023, 12:08:04 PM1/31/23
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Seems to me it would be a credible part these days with momentary switches being so popular? Something in a small case with Vcc in and out, ground and switch input. Crazy price on that Maxim part.

mkr5000

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Jan 31, 2023, 12:14:43 PM1/31/23
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Do they make an on/off latching type in those small keyboard type switches. (I say keyboard for lack of a better term). You know, the small 4 pin types?

Ricky

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Jan 31, 2023, 2:23:20 PM1/31/23
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On Tuesday, January 31, 2023 at 1:08:04 PM UTC-4, mkr5000 wrote:
> Seems to me it would be a credible part these days with momentary switches being so popular? Something in a small case with Vcc in and out, ground and switch input. Crazy price on that Maxim part.

Most designs don't need a power supply switch chip. They have an MCU which can implement the same thing, or more accurately, don't ever turn off, because their power is so slow when idle. The CPU senses that the button is pushed, and either puts itself into its lowest power state or actually turns off a pass transistor on the power rail. When the user pushes the button again, it either triggers a "wakeup" input on the MCU, or enables the pass transistor directly.

Not many circuits can't handle a couple of uA drain when "off".

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Rick C.

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Fred Bloggs

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Jan 31, 2023, 2:29:51 PM1/31/23
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On Tuesday, January 31, 2023 at 12:14:43 PM UTC-5, mkr5000 wrote:
> Do they make an on/off latching type in those small keyboard type switches. (I say keyboard for lack of a better term). You know, the small 4 pin types?

Yes- even amazon sells them.
Can't really vouch for them, but they're the basic type you want.

https://www.amazon.com/Uxcell-a13112600ux0650-12x12x9mm-Latching-Tactile/dp/B00HGAKKAC/ref=sr_1_3

If you want name brand look at Mouser, Digikey, Arrow, similar.
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