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Simple Li-Ion monitoring circuit

Hello,

I have a 7.4V Li-ion battery (or rather a battery pack). It is connected to the 3.3V DC-DC converter which runs the rest of my circuit.

From what I've found out, I need to shut down the whole circuit when

the battery voltage drops below 6V. The DC-DC converter has enable pin, so I've figured out I just need to connect the monitoring circuit to this pin.

What kind of monitoring circuit would you recommend? I really need something simple, it may be an integrated circuit.

Or maybe it is possible to put this circuit between the battery and the DC-DC converter? So it blocks any current passing, when the battery is low?

Reply to
arybinsky
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check out Texas Inst. TL7702 or google for voltage supervisors

martin

Reply to
martin griffith

I have used the MAX8212 in the past, you can get them from Digikey

Regards

AJ

Reply to
AJ

Anywhere between 5.8 and 6.6 should be fine, and there's almost no energy to be had between those voltages (very steep slope). This means you can use cheap, high-tolerance parts to set your cutoff with very little loss of usable energy.

All you need, then, are two resistors, a voltage reference, and a comparator. The voltage supervisory chips suggested by others combine the reference and the comparator without costing much more, although they may be more complicated than what you need and I haven't looked at their power consumption.

I would recommend looking at the quiescent current of whatever you pick

- you don't want your cutoff circuit itself drawing the battery down below 2v per cell and ruining it even after the main circuit has been shut down.

Reply to
Terran Melconian

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