Designing LiFePo4 based charging circuit

[anso-engineer]

Hello, I plan to use in my circuit CN3058E charger. Here is the application example from the datasheet.
Probably I dont need NTC, they say as this: "The temperature sense function can be disabled by grounding the TEMP pin"
I suppose then I don't need R1 and R2 also?

[sleemanj]

Correct

[anso-engineer]

And extra question, when we say  that charge is terminated is it safe to allows it stays connected to the battery in constant manner?

[mariush]

Depending on your charge current and your input voltage, you may want to add a diode before the Vin, a plain 1n4007/M7 diode for example. This way you'll have some voltage drop across the diode and the charge chip will dissipate less energy as heat when it's regulating the input voltage down to 3.0v ... 3.6v

The datasheet says the chip can work with as little as 3.8v, so a diode would drop only around 0.6v-1.0v from your 5v input, which means the IC will still get 4v to 4.4v, well above the 3.8v that's required.   As an added bonus, the diode can also act like a reverse voltage protection.

Last but not least, you may want to have a look at BQ25170 / BQ25170J.... it's not as cheap but fairly close to that, it's not SOIC but still reasonably large in WSON package and easy to solder by hand (pads extend on the side walls so you can wet them with solder easily by hand).

BQ25170 : https://www.lcsc.com/product-detail/C5208201.html

BQ25170J (jeita compliant) : https://www.lcsc.com/product-detail/C3682876.html or https://www.digikey.com/en/products/detail/texas-instruments/BQ25170JDSGR/15856833

The Digikey link has the datasheet in English

Reasons... not relying on a single source, you can get it from Digikey, Mouser etc , and you can also set the charge voltage to 3.5v if you want to extend the life of your battery pack etc etc

[anso-engineer]

Firstly I plan to concentrate on CN3058E. Also I have bought 10 items.
But, one thing that isn't clear for me, how it orientates? 🤔

Normally on the pin assignement (or other views) is shown some visual identifiers, titles, dots etc. But here I have to leave it on my imagination.
Is this doe or cricle, shown on "Package information" located near to the 5 - BAT PIN?

[sleemanj]

The dot is pin 1

You can see on this photo of my own board using that chip

https://d2x7gdstplisc7.cloudfront.net/.tmp/assets/_site_/images/products/lithium/lifepo4-charger/v2/1200x/padded/1200x/FFFFFF/P1060083.jpg

[anso-engineer]

The dot is pin 1

Great, you example is demonstrative.
Is it common rule that dot matches first pin? Because there is no projection view which clearly shows it.

[anso-engineer]

Already good post about identification first pin on chip:
https://embedded.fm/blog/2017/5/30/looking-out-for-number-1