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BQ77915EVM-014: Fault Protection Test Result is different from datasheet.

Part Number: BQ77915EVM-014
Other Parts Discussed in Thread: BQ77915

Hello,

Customer tests fault protection with BQ77915EVM.

But its test result is different from datasheet as below.

Tested both condition of  5 Cells (1 EVM) and 10 Cells (2 EVM)

Used Power Supply for CHG and Electric Load for DSG.

Could you let me know why test result is different from datasheet description?

Regards,

Nicky

  • Hi Nicky,
    When testing with an electronic load, the load will pull up the PACK- pin on a discharge fault. In the standard circuit for the charge FET gate drive such as figure 24 of the bq77915 data sheet there is a resistor and diode to allow gate drive when ON and limit current into the CHG pin when PACK- is pulled up. The electronic load can pull up PACK- and the charge FET gate due to the discharge fault while the CHG pin is driven low.
    Also note that some electronic loads have a residual load for their terminal measurement circuitry even when the load is disabled. Check the equipment specification for the load value.
    Please have the customer check the CHG pin without the load attached, although the LD pulldown will attempt to recover from the fault, so the observation may have to be made during transition, or with the PACK- voltage controlled.