My circuit has a few ground references and I'm unsure how best to connect them.
I have a solar battery charging module: GV-5-MOD (datasheet) and it has a several relevant terminals:
- PANEL-
- BATTERY+/PANEL+ (shared)
- BATTERY-
- LOAD-
- LOAD+
Since my SBC and its peripheral sensors are my load, I am running it from LOAD+ and LOAD-, so I expect LOAD- will be my main GND reference.
I have a fuel gauge IC I want to use to track battery state of charge: LTC2959 (datasheet). From the typical application diagram...
...it should be powered from the charger (BATTERY+ terminal on the charger), have the battery's positive terminal connected to the SENSEN pin, and battery's negative terminal connected to the GND pin. But it says the battery's negative terminal and SBC GND should be one and the same in contradiction with the charger which has a separate BATTERY- and LOAD- terminal.
Options I see are:
tie BATTERY- and LOAD- together. I suspect this will bypass some low side MOSFET, AKA protection circuitry like LVD?
Use BATTERY- as the GND reference of the LTC2959 and LOAD- as the GND reference of the SBC. Won't these be at different potentials if there's a drop across RDS_on of the the charger's low side mosfet? Should a level shifter/converter be used here?
Use LOAD- at the GND pin of the LTC2959. I think this wouldn't affect charge counting or current measurements by the IC but would add a load-current dependent error to the IC's battery voltage readings.
What should I do?
In terms of board layout, if I'm routing these signals over two different ground planes with a gap between, is there anything I should do when traversing the split to minimize EMI?
