lowvoltage threshold detector :-)

I want to monitor a discharged point on battery life and report that on a cmos pin,

i need something below 1v, something like .7v to .9v,

i tough i found the nice solution with Microchip TC54 but they go down only to 1.4v as threshold ...
any good better fit parts ?

i tought i can use some other simple circuits to do that but, it is a bit hard for my to dig out my old opamp stuff so .. any suggestion ?

just some comparator? possibly even inside the mircrocontroller or something?

voltage comparator, LM393.

Do you have another source of power to run the monitor circuitry? Or is it also powered from the battery?

ChrisP58 said:

Do you have another source of power to run the monitor circuitry? Or is it also powered from the battery?

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what i like about the TC54 was it includes the voltage reference and it can use variable Vcc but ...

I'm thinking something like that with a voltage comparator...

battery will go throught a step up converter ( a have few of those for prototyping) and become a steady 5v, so i guess i will take my power there and make a resistor voltage divider for reference side of the comparator, i tought also about a zener diode for really stable reference but i don't think if i really need it ... the other side of the comparator will sense the battery .

LM393 or LM339 ? they seems to be pretty much the same thing and I might have few 339 in a bottom of my hobby junk/parts box

so what do you think ?

this home project is my first adventure far from the software side
now time to shovel some snow left by the last storm

The LM339 is a quad, and ther LM393 is a dual, but they are both the same part.

Typically, a zener is used for a stable reference, but if you have a 5V reference (coming off your boost supply), then you don't need a zener.

If you Google "comparator with reference voltage" there will be several different devices listed that should do what you want.

crutschow said:

If you Google "comparator with reference voltage" there will be several different devices listed that should do what you want.

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Thanks a lot for your enlightening answer !
but i think i would have suggest go to major vendors and manufacturers search for comparator with voltage reference instead...

voidptr said:

Thanks a lot for your enlightening answer !
but i think i would have suggest go to major vendors and manufacturers search for comparator with voltage reference instead...

Click to expand...

Don't understand your comment. The Google search turned up several major vendors of those devices.