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BQ20Z75 DFETF Calibration assert

simon buchwald
Intellectual 745 points


Hi There,

Its been a while since I last posted, but I have found something I cant explain and I am hoping someone from TI can assist again. (Tom?)

So I have a sample space of 10 boards using the BQ20Z75 parts, and most of them calibrate just fine using BQEASY.

A couple of boards seem to assert DFETF during current calibration. FET fail time is set to 5s. Current calibration with a 2A discharge current from a current limited supply is applied directly across the current sense resistors, but it usually takes longer than 5s during calibration. When I have finished calibration on 2 of the 10 boards, DFETF is asserted.

If I disable FET Fail Time by setting it to 0, then do the calibration, then reset FET Fail Time to 5, and continue on with a 41 and 21 command to the device, it asserts QEN ok and starts charging.

Can anyone suggest why some devices are reporting DFETF and others not whilst using the same calibration process.

Thanks in advance.

Simon Buchwald
Amatek Design
Sydney Australia