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BQ2031 Battery Qualification Test disrupted by analog volt meter across the BAT+ and BAT- terminals - Solutions?

Saleem Banatwala
Prodigy 190 points
Other Parts Discussed in Thread: BQ2031

Good Morning,

I built the circuit on page 5 of this manual:

http://focus.ti.com/lit/ug/sluu023b/sluu023b.pdf

except I left resistors R15, R16, and R17 out because I don't think I needed them based on my application.  I also used slightly different resistor values for R3 and R2 due to the thermistor that I was using.  I also included an analog ammeter between L1 and BAT+ and an analog voltmeter across BAT+ and BAT-.  The voltmeter seems to be interfering with the TI pre-qualification test and it never gets to the battery absent standby mode if no battery is present.  I notice that it doesn't do this with a digital voltmeter across BAT+ and BAT-.  I am not an electrical engineer so I don't really have the background to troubleshoot this problem.  I can only assume that the current through the analog voltmeter is sufficient to trick the BQ2031 into thinking that a battery is connected.  Can anyone suggest a workaround for this or suggest another reason why this may be happening?

 

Thanks

 

Saleem

  • 0
    TI__Mastermind 31120 points

    Does the circuit work properly with all the components?

    Some designs require a certain input voltage to put the part into battery absent mode.....try raising the input voltage.

    Are you using the EVM or built a circuit using wires....typically one has to have a well designed PWB for good results with a switcher.