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BQ20Z75 - How to disable Gas Gauge

Anthony Thomas
Prodigy 10 points

I have designed the BQ20Z75 into a production tester for a checking out  a charger circuit  in a Medical Monitor  (The monitor in final use will uses a 3 cell lion SMART battery fitted with a BQ20Z75).

Using the BQ20Z75 provided me with the easy method of simulating the smart battery controller, thus allowing me to confirm the monitor establishes communication with the BQ20Z75 at production test.

 

My circuit for the BQ20Z75 is pretty much per the application notes with exception that the individual cell voltages is generated via a resistor divider sourced from the charge voltage. My tester has a shunt regulator to simulate the cells.  In testing as expected I have noted the returned relative state of charge parameter  is inconsistant, usually 0 or 100%.I need this to be constant  (I dont really care what the value is as long as consistant)

My question is there any why I can set the device so that the returned relative state of charge is always the same value. Perhaps Is there a way I can disable the gas guage so that the relative state of charge is unaffected.

 

Hope some can help with perhaps my unusal application for the BQ20Z75

 

Thank you

Anthony Thomas (engineer, Gatmetrix Ltd)

  • 0
    TI__Genius 10235 points

    Anthony,

    You can disable the IT algorithm by writing 0x00 to Update Status in the data flash and then issuing a reset. The Rem Cap register can still change though. Then, you can write a value to the Remaining Capacity register (command 0x0F). However, if you reset the gauge or if there is charge or discharge current the register will change. There is no way to disable that from happening.