E-series power complete bypass

I am interfacing a separate board to the E-series module. I am currently using the E-Series eval module. I want to bypass power management completely on the E-series board as I’m already handling that on my other board. I have 3.3V available and 3.5V available, but the 3.3V is low power. My problem is that the E-series wants to do a bunch of battery charging “stuff” and will only allow me to (through software) input a minimum of 3.88V. I’m planning on doing everything fairly low power and am running off 4-AA batteries in series, and want to use those in the range of 6.4V max down to about 3.6V. I have my own switcher, monitoring, etc. for soft shutdown at min voltage, so I don’t want to use the E-series board to do that stuff. The e-series board will be (hopefully) configured to have the cell modem shut down and in low power mode while idling, come out of low power and connect the cell modem, upload some measurements, then go back to low power.

My problem is the documentation is either very general or only gives me limited options for doing things. I can see the PMIC and various other ICs on the E-series module, so I want to do whatever depopulations, cuts/jumps, etc. are necessary to power the module from another board at a voltage level that isn’t supported by the current configuration.

I would disable charging in the PMIC and supply your regulated 3.5V to the JST battery connector (or the matching through holes on the E series evaluation board).

As long as your power supply can supply short bursts of 1800 mA you should be fine.

(That is a personal recommendation, not an official Particle response. I did try it with an Electron and a bench power supply, and it worked fine in my quick test, however.)

I don’t know if I can supply bursts that high, unless it’s just a matter of putting a big cap on my supply line. And by “JST connector” do you mean J2, the LIPO connector?

Can you provide a specific example of disabling charging? I assume that’s a function call in the setup routine.

Yes, J2.

This code is mostly what you need, but remove the lines disabling the BATFET because if you disable that, you can’t power by the JST battery connector.