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BQ76952: Reverse polarity protection

May
Genius 9880 points
Part Number: BQ76952
Other Parts Discussed in Thread: LM5163

Hi Team,

Good day.

Customer have following questions regarding BQ76952. I'll posting the query of the customer on their behalf. 

"

1. I would like to know if you have any reference designs for the BQ76952 that withstand a full reverse polarity condition on its cell sensing inputs and on its power supply rail.

We currently designed a layout which has TVS Diodes between the inputs for two adjent cells and Schottky Diodes for reverse polarity protection on its inputs to prevent damage to the battery monitor if one cell or even all cells are connected in reverse.


In addition to that we have fuses that should blow and disconnect the cell or whole battery from the bms in a reverse polarity scenario. However our latest test showed, that the IC would be damaged when we connect the whole battery in reverse. The cell inputs were simulated with a resistor ladder. The fuse did blow but the BQ76952 was damaged.

2. In  

with the LM5163 DC/DC converter. Is it possible to protect this DC/DC from a reverse polarity connection with a simple diode or PMOS in series, or are there any limits because of high voltage spikes that can occur at the input?

The battery monitor circuit is nearly identical to the design in the datasheet () the only differences are we use no current sense resistors, so these terminals are connected to ground. And we dont have charge or discharge Fets so those terminals are not connected and there are no temperature sensors. Since we dont use the FETs the connection CD to the linear regulator is connected directly to the cell 16 input.

"

Regards,

Maynard

  • 0
    TI__Guru 54715 points

    Hi Maynard,

    Yesterday's answer does not seem to be here, so this may be a duplicate.

    I entered a separate post for your LM5163 question so it could be answered by a knowledgeable person, they have answered here https://e2e.ti.com/support/power-management/f/196/p/982760/3630889#3630889 

    The BQ76952 is intended for permanent connection to cells with the proper polarity.  It does not have protection for reversed cells. There is no reference design for reversed cell protection.  A reversed cell or open cell stack will typically damage the IC by exceeding the abs max of the inputs and forcing current through unexpected paths.

    If the SRP and SRN are not used they should be grounded to VSS.  If FETs are not used supplying the linear regulator NPN collector path to cell 16 is correct.