• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 177 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25756: 10-Cell Bidirectional Battery charger

GIEDI WANG
Prodigy 40 points
Part Number: BQ25756
Other Parts Discussed in Thread: TPS25751, BQ25758

Tool/software:

Hi Team,

We use  BQ25756 in one of 10-Cell Bidirectional Battery charger project.  TPS25751 support 5V/9V DFP for BQ25756.

We use our TPS25751 i2cm to control the BQ25756, when in DFP, TPS25751 will send the i2c command to BQ, and generate the PDO voltage value.

Stable load mode : 5.15V / 0A , 4.40V / 3A ； 9.30V / 0A , 8.55V / 3A

Dynamic load mode: 5.40V / 0A , 4.15V / 3A ； 9.55V / 0A , 8.20V / 3A   (Over shoot / Under shoot)

1. How to compensate the BQ25756 DFP voltage drop ?

2. How to avoid the BQ25756 DFP voltage over shoot / under shoot ?

Thanks and Regards,

Giedi Wang

  • 0
    TI__Expert 6385 points

    Hi Giedi,

    Is the BQ25756 in reverse mode for this application?

    GIEDI WANG said:
    1. How to compensate the BQ25756 DFP voltage drop ?

    Are you referring to a voltage drop across a cable or is this voltage drop at the BQ25756 pin?

    GIEDI WANG said:
    2. How to avoid the BQ25756 DFP voltage over shoot / under shoot ?

    Can you provide a waveform of this? What is the dynamic load condition? How does the voltage respond?

    Best,
    Michael

  • 0 in reply to Michael Bradbourne
    Prodigy 40 points
    Q1:
    Giedi Said : How to compensate the BQ25756 DFP voltage drop ?
    Michael Said: Are you referring to a voltage drop across a cable or is this voltage drop at the BQ25756 pin?
    Giedi Said :  A voltage drop across a customer specified cables.
    Q2:
    Giedi Said : How to avoid the BQ25756 DFP voltage over shoot / under shoot ?
    Michael Said :Can you provide a waveform of this? What is the dynamic load condition? How does the voltage respond?
    Giedi Said :  The waveform is shown in the figure.
  • 0 in reply to GIEDI WANG
    TI__Expert 6385 points

    Hi Giedi,

    This application note shows how to use some external circuitry to compensate for the cable losses:

    The BQ25758 is very similar to the BQ25756. The main difference is that it is just a buck-boost controller rather than a charge controller. Let me know if this can help with the voltage drop across the cables.

    With regard to the overshoot and undershoot waveforms, it looks like the lower constant value is the voltage drop across the cable. Is this correct?

    Best,
    Michael