New BQ25895 5A lithium charger breakout, improvements all around
bq25895 IC description
(Manufacturer product page)bq25895 I2C Controlled Single Cell 5-A Fast Charger with MaxChargeTM for High Input Voltage and Adjustable Voltage 3.1-A Boost Operation (Rev. A)
Some renewed interest in my BQ25895 breakout board warranted a few design changes to the original: The tantalum capacitor has been replaced with a few extra ceramics (all ceramics seems to improve performance), an extra screw terminal has been added to SYS pins (nice feature when adding an additional boost converter), swapped inductor (smaller footprint), added input pins in parallel with USBin, added footprint for optional diode (greater boost current capacity on PMID) and exposed some copper for better thermal performance.
To get the IC up and running, add a 10KΩ resistor from REGN pin to TS pin, and a 10KΩ resistor from the TS pin to GND (for designs where a thermistor is not required). Also add a 260Ω resistor from the ILIM pin to GND (sets charge current limit, see datasheet for more information). Finally, add a resistor from /CE to ground to enable charging, something like 10KΩ.
The IC will function autonomously but full I2c control is possibe. Many config settings can be tweaked, charge current limit, PMID voltage etc but be aware a watchdog timer has to be reset every now and then to keep your settings active.
A word of caution: Always take care when messing about with lithium batteries, failure to observe proper charging guidelines is like throwing water on a fat fire… it’ll take your face off. Read up on safety here, here or here. Use all of the above at own risk!
Find the parts online or try these suppliers
- Micro USB connector: Get them on eBay
- Inductor: Get it from Coilcraft or Mouser
- Screw terminals KF301 2P: Widely available but try eBay, 5.08mm pin pitch
- BQ25895 charger IC: Buy direct from TI or Mouser