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BQ40Z50: Disabling FUSE while using PTC protection

Abd Mo
Prodigy 60 points
Part Number: BQ40Z50

Hello,

Two questions regarding BQ40Z50-R3 for rechargeable BMS system where PTC protection is enabled and FUSE is disabled:

1- How to disable FUSE bin from BQ40z50-R3 Data Memory so it does not activated when PTC protection is activated? 

In BQ40z50 > Data Memory > Settings > PF Fuse C & PF Enabled PF C,
I only enabled the PTC in PF Enabled PF C
And I ensured that it is disabled in PF Fuse C
and FUSE_EN also disabled

for more Data Memory details check BQ40z50R3.gg.csv

2- How to disable the FUSE bin by hardware while having minimal current?

It was suggested in https://training.ti.com/troubleshooting-common-multi-cell-gauge-issues 
to connect the FUSE bin directly to VSS in case of disabling the FUSE. But when I test this suggestion, by connecting it to GND directly as shown in next figure. The circuit start to consume 4 mA  when PTC protection trips and FUSE bin is activated. So can I use different value of R1 to reduce the current? And what the suggested value?

(Similar circuit which we used in the BMS design)

  • +1
    TI__Intellectual 2146 points

    Hi Abd,

    1. I don't believe the fuse pin activation can be disabled. The PTC protection is a hardware feature and so toggling FUSE_EN does not affect the feature's activation of the fuse pin.

    2. You can place a larger resistor from the fuse pin to ground. From the datasheet the max voltage of the fuse pin is 8.65V so you can use that to determine the max current.