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It's my first time designing a PCB and my first time posting to this website (so yeah, I'll be a bit of a mess). I've got a few questions regarding the pins labeled VTHERM and VTH_REF, a thermistor labeled RREF, and a Li-Ion battery, all shown at the right side in the image below.

enter image description here

My questions are:

1) How do I wire the two pins and the thermistor to the battery when the battery is drawn with 4 leads? Are there any 4 lead Li-Ion batteries? I've seen mobile phone batteries with 3 leads, maybe that's the case?

2) Do I need this whole Thermistor jazz if I'm expecting temperatures of around 40C during the day? Can I leave the pins NC?

3) Can this IC solution charge a Lithium Ion Polymer battery if it mentions it's designed for a Lithium Ion Battery?

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  • \$\begingroup\$ I believe your questions are answered in the data sheet for this IC. \$\endgroup\$ – Barry Aug 20 '16 at 23:24
  • \$\begingroup\$ related to item 1) : Why are there 3 pins on some batteries? \$\endgroup\$ – Nick Alexeev Aug 20 '16 at 23:46
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    \$\begingroup\$ We are not here to read the datasheet to you. You also haven't linked to the datasheet, so we can't tell what this chip is supposed to do either. You can ask specific question about not understanding what the datasheet is saying, but those need to show effort in reading the datasheet, and must point to the specific passages you are confused by. As it stands, this answer needs to be closed. \$\endgroup\$ – Olin Lathrop Aug 20 '16 at 23:49
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  1. If the LiPo battery has no thermistor, the you must add one, either 10k or 100K with same value for Rref. If not bonded to the battery, then allow some ? thermal drop and attach to a copper sheet base holder that makes contact with bonded thermistor and battery.

Why?

"The regulation voltage as well as the 1C charging current can be set to change based on the battery temperature."

  1. Not really, but you can fake it with fixed R values, for sub-optimal CV levels vs temp.

  2. yes, depending on your attention to all spec details.

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  • \$\begingroup\$ Than you Mr Stewart You're a life saver :D \$\endgroup\$ – Seifeldin Hashem Aug 21 '16 at 0:41
  • \$\begingroup\$ @SeifeldinHashem By the way, watch a video of a lithium battery fire and ponder. \$\endgroup\$ – Nick Alexeev Aug 21 '16 at 0:43
  • \$\begingroup\$ I've seen those ( yikes :o ) \$\endgroup\$ – Seifeldin Hashem Aug 21 '16 at 0:56

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