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BQ76952: BQ76952EVM

Sachin Agrawal1
Intellectual 285 points
Part Number: BQ76952

We reviewed BQ76952 EVM design to build our own BMS 48V/50Amp standalone product. 

BQ76952 EVM support only 6amp circuit. We would like TI support to help us suggest what changes we should make for CHG/DSG/PCHG circuit to be able to handle 50Amp continuous current / 100Amp peak current.

Appreciate your quick response.

Best regards,
Sachin

  • 0
    TI__Guru 54715 points

    Hi Sachin,

    The BQ76952 EVM is rated up to 72V, so 100V FETs may not be adequate for such a design and 150V FETs were selected.  Transients are common in batteries, and they may have regulatory over-charge testing required, so having the FET rated for 150-200 % of the charging voltage is common.  If reverse charging tolerance is needed the discharge FET should be about 2X or more of the charging voltage since the reversed charger could be attached to a fully charged battery. Higher voltage FETs have higher RDSON resulting in higher heat and lower current limits to maintain a particular temperature limit.  If you can use a lower voltage FET you can select one with lower RDSON and will have less heat.  You will need thermal control in your design to handle the dissipation from the FETs.  Consider how much power you can allow in the battery, how much heat will flow out, what heating you can tolerate of the cells. This will let you select a FET with an appropriate RDSON.  You might also parallel FETs for lower total resistance and to spread the heat that is present.  See the application note https://www.ti.com/lit/pdf/sluaa09, it may be helpful in using multiple FETs.

  • 0 in reply to WM5295
    Intellectual 285 points

    What about 50Amp current handling?

    1) Do FET used in EVM will be appropriate for 50Amp continuous current handling? Do any part of circuit (parts) around FET for CHG, DCHG, PCHG, LD, PACK pins will change?

    I would like to share schematic for review? Can we do that? 

    Best Regards,
    Sachin

  • 0 in reply to Sachin Agrawal1
    TI__Guru 54715 points

    Hi Sachin,

    The FET from the EVM shows a maximum continuous current of 56A with Tc = 25C and 36A with Tc = 100C.  You will likely need a different FET or 2 or more in parallel to support 50A continuous. 

    When paralleling FETs you may need to adjust the resistance to the gate for appropriate switching speed, and perhaps use a small resistance or bead to isolate the gates from each other depending on the FET selected.

    The precharge resistor on the EVM supports a low current for demonstration.  You may want a smaller value for higher current if you can support the heat from the resistor, and check the FET current and power rating.

    We can look at your schematic for implementation of the BQ76952.  You will need to be confident in your component selection, it is your system design.  Don't post proprietary information, exclude that or send the schematic in a private message.

  • 0 in reply to WM5295
    Intellectual 285 points

    Thanks!

    Please let me know email id at which i can correspond with TI for schematic review support.

    Secondly, i want to know stock availability support. We have of mass production requirement in March, April & May requirement. So would BQ76952 parts for qty -6k be available in mid Feb? Kindly confirm.

    Thereafter we can work on annual projection based production plan. Kindly suggest quickly.

    best regards,
    Sachin

  • 0 in reply to Sachin Agrawal1
    TI__Genius 10830 points

    Hi Sachin,
    Thank you for your interest in BQ76952. BQ76952 is in full production (ACTIVE) and we will have parts on the TI Store very shortly (in the next week or so).

    I suggest you set up an alert on store.ti.com as per the screen capture below. 

  • 0 in reply to David Hien
    TI__Guru 54715 points

    Hi Sachin,

    See the videos and application notes for the device in the product folder for development assistance.  If you would like us to look at the schematic you can send a private message to a recipient with the friend request if your schematic has information which should not be shared.  

  • 0 in reply to David Hien
    Intellectual 285 points

    Dear David,

    If we plan production from Feb onwards & want to procure 2k pieces each month then can I request TI confirmation:

    that it would be safe if we depend on BQ76952 stock availability. Please confirm once more.

    Secondly, we would like TI support for design review. Which Email ID I can correspond onto- please suggest?

    I would like to immediately go with prototyping process. FYI- We would like to switch from existing AFE to BQ76952IC.

    Best Regards,

    Sachin

  • 0 in reply to Sachin Agrawal1
    TI__Genius 10830 points

    hi Sachin,
    Please check the inventory on store.ti.com as I indicated: BQ76952PFBR parts are back in stock.

    WM5295 answered your 2nd question earlier today.