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Original question:

BQ76952: PACK and LD pins in case of Single Relay (instead of CHG and DSCHG high side mosfets)

BQ76952: How to control relay instead of CHG DSG FET Combo using one pin

Steven Shenker
Intellectual 930 points
Part Number: BQ76952

Hi there,

I recently asked a question on the feasibility of using a relay instead of mosfets. I have now got a relay control circuit hooked up to the DDSG pin which will open/close the main relay like the DSG pin would normally do (in the case of mosfets) in an OCD / UV situation. 

One problem with this setup is it will not function in an OCC / OV situation. Is there anyway to configure the BQ76952 via firmware to Set LOW the DSG pin (and also therefore the DDSG pin) in the case of an OCC / OV situation as well? 

Thanks in advance for your help,

Steven 

  • 0
    TI__Mastermind 42060 points

    Hello Steven,

    The DSG driver (which would include how DDSG behaves) does not have a setting to turn-off during a COV/OCC. A relay was not in mind when originally designing these protections.

    You would have to send a command manually to turn DSG OFF (The DSG_DSG_OFF() command) or use one of the external pins to turn off DDSG (The DFETOFF pin), this would have to be done by your microcontroller. 

    How are you placing the relays in this system in relation to DDSG/DCHG? Are you controlling two different relays for each DDSG/DCHG? Are they in different paths? 

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Intellectual 930 points

    HI Luis,

    Thanks for your reply. In our case we only have one relay attached to the DDSG pin, I guess we could come up with a AND / OR strategy in future to combine the DDSG and DCHG pins to control the single relay.

    For now I will take your advice and send commands.

    Thanks again,

    Steven

  • +1 in reply to Steven Shenker
    TI__Mastermind 42060 points

    Hello Steven,

    Understood. Yes, in the future I believe AND'ing the DDSG and DCHG would work. Whenever a fault causes DDSG or DCHG to turn-off, the AND logic would go low and turn-off the relay.

    Best of luck in your design!

    Best Regards,

    Luis Hernandez Salomon