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I've designed a circuit using an MCP73871 (link below) and some lithium ion 18650 cells. I'm confused by the under-voltage lock-out (UVLO) on that chip as it's not clear (to me at least!) whether it stops devices draining the cells when they get too low, or whether it just turns itself off, and therefore requires some other way to cut the current-draw off.

Can anyone throw any light on this, and if I do need a separate low-voltage disconnect, could anyone recommend a solution please?

http://ww1.microchip.com/downloads/en/DeviceDoc/20002090C.pdf

[EDIT] Having tested the circuit, there's 2mA draw from the "out" pins, when the supply voltage is <2.5V. Should it shut that load off or does that require a separate mosfet and control circuit/IC?

thanks, Danny

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Update

Obviously something is drawing more current than the spec of; "Modes of Operation Without Battery Charger Enabled

– NORMAL Mode ICC = 4 μA – Shutdown Iq = 100 nA"

Usual debug mode is verify against test circuit in datasheet on each pin and suspect ESD possible leakage damage , change IC, then consult with OEM Forum for technical support.

Which pins are drawing the current?

If you shut off the battery then you will lack the sensing to recover with a charger unless manually reset. Is that OK?

enter image description here

Other info

It switches the input off to prevent further drain to battery but senses before and after switch.

enter image description here

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  • \$\begingroup\$ Hi Tony, thanks for the info, but I'm not sure I follow. I've just edited my post as, having re-read it I missed some info and have measured the load. I'm getting 2mA power draw from an Atmega chip which is stuck in brown-out because of the low voltage. I just want the circuit to be off so the cells are protected. \$\endgroup\$
    – dannydc
    Nov 1, 2016 at 23:57
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    \$\begingroup\$ I consider those who drop by with -1 and no comment as trolls . either contribute or help or say something intelligent \$\endgroup\$
    – Tony Stewart EE75
    Nov 2, 2016 at 0:32
  • \$\begingroup\$ In case it's of use to anyone, or anyone can confirm/recommend something else, I'm looking at using this in conjunction with the MCP73871: ti.com/lit/ds/symlink/bq2972.pdf \$\endgroup\$
    – dannydc
    Nov 5, 2016 at 17:03

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