single cell lithium charge IC - i could use a hand please...  - Page 1
Forum section: electronics / projects

author: bigjoncoop
author_rank: Regular Contributor
timestamp: October 04, 2021, 10:10:17 am
content: hey fella'sI'm designing a circuit and need to add a single cell lithium charging circuit onboard. I know there are a lot of premade solutions on the market but in my case I need it to be as small as possible.so I decided to purchase some DIO5508XS8 IC's made by DIOO.http://www.dioo.com/uploads/product/20190312/2f1b7589f0068b2e7cdfd9a2c89d8736.pdfI would have used the TP4056 IC's but not readily available from the USA at the moment.The DIO5508 features are perfect for my application. 5V Input and a programmable charge current up to 1A.The typical circuit diagram is fairly straight forward and uses few components.(circuit diagram below)In the PDF it indicates which resistor values to use to set the different parameters. which I believe the the main one I need to be concerned about is one that sets the charge current... and since my rechargeable lithium coin cell doesn't have a built in NTC thermistor I just need to GND the temp pin to disable it.Basically I'm hoping someone with the know how / knowledge could take a quick look at the datasheet and just confirm that the only 2 pins i need to set is the temp pin which I'm just going to tie to GND and the pin that set the charge current and exactly how to set it using which value resistor...- Attachments and other options

author: enut11
author_rank: Super Contributor
timestamp: October 05, 2021, 05:25:45 am
content: See if this 1S pcb is suitable. Available from Aus.https://www.ebay.com.au/itm/313446496131?hash=item48faddf783:g:gSgAAOSwUuRgRc-C

author: thinkfat
author_rank: Unknown
timestamp: October 05, 2021, 08:31:22 am
content: You will find the answers to both questions on page 2 of the datasheet, literally spelled out in the description of pin 1 and 2.

author: wraper
author_rank: Unknown
timestamp: October 05, 2021, 08:33:49 am
content: Quote from: enut11 on October 05, 2021, 05:25:45 amThis is a battery protection circuit, nothing to do with charging.

author: enut11
author_rank: Super Contributor
timestamp: October 05, 2021, 09:22:29 am
content: According to this video, it does both. You need to FF to the explanation. I assume some sort of current limit would be needed.

author: wraper
author_rank: Unknown
timestamp: October 05, 2021, 09:34:20 am
content: Quote from: enut11 on October 05, 2021, 09:22:29 amNo it doesn't. From the video it's obvious that it's only a protection circuit. Nor your comment was actually relevant to the question asked.QuoteFYI it's part of what the charger does.

author: thinkfat
author_rank: Unknown
timestamp: October 05, 2021, 09:38:32 am
content: Yes, there's a current limit, but it's on discharge, not on charge. It's basically a short-circuit protection. The other functions of this chip are a charge-stop when the battery voltage reaches critical level, and an undervoltage lock-out on discharge. But there's no overcurrent protection on the charge path. A separate charger circuit needs to provide this.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 05, 2021, 09:40:16 am
content: Yes, protection is protection and charger is charger. You usually want both.Charger is current control, voltage control and a bit of other logic possibly including timers, temperature checks etc.Protection has three purposes:1) low voltage cutoff, which charger does not provide2) high voltage cutoff, which chargerdoesprovide, but the protector adds another layer of safety if the charger fails or if there is another unexpected "charger" somewhere.3) overcurrent protection (including short-circuit), which charger does not provide when the load is discharging the cell.