Hello,
I am in the process of prototyping small wearable electronic device which uses BQ27742 for battery management. It's DSBGA package is quite demanding for PCB manufacturers.
My story is that I am not able to escape with the signal trace from the BAT pin using top layer. I can't meet most of the PCB manufacturers requirement when in terms of minimum trace width (4 mils or ) or clearance (4 mils or ) to run proper "fan out". My PCB pads with NSMD style have diameter 0.25 mm. I want to stick with 2 layer board if possible so using microvia to connect to bottom layer is also not an option.
There for my idea is to connect VPWR and and BAT pins together and use RC filter with good C decoupling.
According to datasheet BQ current consumption by VPWR pin will be around 167 uA, and with 10R resistor in filter voltage drops on BAT pin should be less than 1.7 mA. I've never worked with any battery management systems before but I assume filter is required to filter out voltage drops on battery during system current consumption peaks if there are any due to its series resistance. Maybe reducing R in it to let say 5R won't hurt so much and will reduce voltage drops from VPWR by half?
Are there any other issues except voltage drop from VPWR I might expect if I connect VPWR and BAT together? Battery will be some kind of 3V cell coin rechargeable battery.
Thx,
Michal Miszczyszyn