BQ27427: BQ27427 & BQ25306 Connection

Hello,

This question has been assigned and will be reviewed when possible by a member of the team.

Thank you,
Alan

The SRX pin must be connected to the application's power supply rail (the same as the charger). If you connect this to GND and BAT to the positive cell terminal then you effectively create a short-circuit (with the internal sense resistor that is just a few mOhm) and burn up the gauge.

According to you, SRX pin should be connected to charger+, right?

Then, is it correct to connect to the SW pin of BQ25306RTER?

The idea is that the BAT pin measures the battery voltage and that the internal sense resistor measures the current into/out of the battery. Hence you can view this as SRX becoming the main power supply node for the system.

hi

I don't really understand.

So in the circuit diagram above, is it okay to connect STX pin to V_BAT?

A discharge current must flow from the positive cell terminal into BAT, through the internal sense resistor and out of SRX.

A charge current must flow into SRX, through the internal sense resistor and out of BAT into the positive cell terminal.

So you can view the battery and the gauge as one unit (pack) where SRX essentially becomes the positive power terminal of "the pack".

According to you, SRX should be VSYS, right? That is, it will power the battery-powered circuit?

Should I revise the circuit diagram like the document I attached?

In other words, should the output pin of SRX connect to the VIN of the step-down IC?

I can't comment on the charger and regulator but the gauge circuit looks correct. I recommend a simple thought experiment: View the battery and gauge as one unit, a black box. SRX becomes the positive power terminal of this black box. Your charger and regulator and anything else in your application will source/sink current from this pin.