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BQ2000: BQ2000's design question

Andy_Lin
Intellectual 2220 points
Part Number: BQ2000

Hi Team ,

My customer is using BQ2000 as  solution for their application , and they are refer the EVM to build schematic for their design  

their using case is : 5Vin to charge 3 cell NiMH battery with current rating 1~2A ,

according the customer using case above, which parts of EVM's design needed to adjust to fit their application?

the following questions regrading EVM's design as below:

1.  what's D6 and Q4 use for?Is D6 is use for provide an regulated voltage for U1 VCC? Are they neglectable for customer design?

2.  what the circuit (Q2,D5,R12) close to Hi side MOS Q1  (in red circle) use for ?

please kindly help to provide the answer , many thanks!

Andy

  • 0
    TI__Guru*** 143910 points

    Hi Andy,

    For 5V input power, D6, R10, Q4 form a linear regulator to step down the input voltage to VCC.

    Q2, R12, C9 and D5 form a speed up circuit for fast PFET turn off.  It or something similar is recommended for higher efficiency. 

    D7 is a voltage clamp to prevent OVP on the PFET gate at turn off for high VIN and will also help with fast turn off. 

    We haven't tested this device in configurations other than the EVM.  Therefore, I can't warranty operation if you change from the EVM schematic.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Intellectual 2220 points

    Hi Jeff,

    thanks for your response, so from your reply,

    1.I assume that D6, R10, Q4 can remove since there's no needed to step down for VCC if DC in is from USB 5V.

    (according customer's applcation)

    2. we should keep Q2, R12, C9 and D5,D7 for fast PFET turn off to increase efficiency and OVP protection. 

    3. Customer will build the schematic according their design requirement, we can review the schematic and have them test on their side for verification.

    correct me if I'm wrong for the assumption above, many thanks!

    Andy

  • 0 in reply to Andy_Lin
    TI__Guru*** 143910 points

    Andy,

    Regarding 1, agree.

    Regarding 2, D7 zener isn't needed since input voltage is only 5V.  I suggest testing with and without Q2,R12 and C9.

    Regarding 3, agree.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Intellectual 2220 points

    Hi Jeff,

    Got it , thanks for suggestion , I will forward these message to my customer .

    Andy