This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ40Z60, DSG won't turn on

Other Parts Discussed in Thread: BQ40Z60

Hi,

I'm bringing up a custom PCB based on the bq40z60.  It's essentially the EVM circuit but with the secondary protection IC and fuse removed.  It's being used with a 3S LiPo battery and a ~16.7V "VAC" source.  I've been unable to get the DSG FET to remain on and provide power to the system.  The load is small - about 40mA.

Attached is a screen shot and a gg.csv file.  I'd appreciate it if someone could take a look and point out anything misconfigured that I've missed.


Thanks.

 Initial.gg.zip

  • Jim

    The AOLD fault is preventing the DSG FET from turning on. I checked your gg file and there is not a parameter setup problem. You will need to check the voltage between SRP and SRN on the device to make sure that there is not a voltage causing the gauge to think that an over load condition is present. 

    tom

  • Hi Tom,

    On further investigation, it appears the fault is real.  The 40q60 is turning on the Discharge FET at the same time as it turns on the Low-side FET, creating a path to ground through L1.  It shuts off after 30ms, but the inductor is still getting hot.

    Is it expected that the 40z60 would be turning on the low-side FET at the same time as the Discharge FET?

    Thanks.

  • There should be some dead time between the signals, but I seem to recall that it is smaller for one edge. Do you have fairly sharp transition times? What is the saturation current rating for your inductor?
  • LODRV (green trace) and DSG (blue trace) are shown in the image below.  L1 has a saturation current of 2.5A, chosen based on a charging current of 1A and a ripple current of ~0.4A.