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BQ25756E: CC and CV alone in Standalone Mode

Abishek V
Prodigy 175 points
Part Number: BQ25756E
Other Parts Discussed in Thread: BQ25750, BQ25756

Tool/software:

I need to just charge the Battery with Constant current (CC) and Constant voltage (CV) with dynamic programmable Constant current up to 10A

Please confirm whether we can use BQ25756E in just CC and CV in standalone mode without use of I2C Interface and no additional charging modes

Also Please let know how to dynamically program Constant current (CC) up to 10A

  • 0
    TI__Expert 6755 points

    Hi,

    The BQ25756E can do CC and CV in standalone. You will have to be able to change the resistance on the ICHG pin to do this. This would likely mean some sort of digital potentiometer. You will not be able to change the precharge functionality, however.

    Best regards,
    Michael Bradbourne

  • 0 in reply to Michael Bradbourne
    Prodigy 175 points

    Thanks for the response Michael

    I need to do charge and no charge with the switching frequency of 1kHz. Can I just toggle the Charge Enable Pin (CE) with frequency of 1kHz to achieve this

    Or is there any better efficient way to do this

  • 0 in reply to Abishek V
    TI__Expert 6755 points

    Hi Abishek,

    What is the application of toggling the charge? Toggling the /CE pin should toggle the charge, but it may not achieve what you want.

    Best,
    Michael

  • 0 in reply to Michael Bradbourne
    Prodigy 175 points

    Hi Michael,

    For Battery diagnostics (Impedance measurement) application I need this kind of the toggling of charging

    Kindly let know CE toggling can achieve this

    Thanks

    Abishek V

  • 0 in reply to Abishek V
    TI__Expert 6755 points

    Hi,

    Will the impedance measurement be taken by an external device while the current is supplied by the BQ25756E?

    Best,
    Michael

  • 0 in reply to Michael Bradbourne
    Prodigy 175 points

    Hi Michael

    Yes. Based on the voltage and current values, the measurement is done externally. BQ25756E supply the pulsed current on 1kHz

    Whether using a external MOSFET at charging output to battery path is better approach or toggling the CE is better?

    Because The response time of toggling the CE with 1kHz in BQ25756E will affect the pulsed charging

    Please let know your suggestion on this

    Thanks

    Abishek V

  • 0 in reply to Abishek V
    TI__Expert 6755 points

    Hi Abishek,

    These waveforms are taken from the datasheet. I am concerned about the delay of the /CE pin for this application. I don't think the toggling will work for impedance measurements.

    Adding a MOSFET to the output battery path may be better, but I would also be concerned about the device continuing to charge up the output capacitors to the full charge, terminating, and taking a while to start back up charging.

    Best regards,
    Michael

  • 0 in reply to Michael Bradbourne
    Prodigy 175 points

    Hi Michael

    I have few queries and it is listed below

    1) What will be output voltage of the BQ25756E if I disconnect the battery from the charger IC during the CC Charging process

    2) What will be Load transient response of the BQ25756E if the battery is connected and disconnected. Also confirm on the time response of BQ25756E load transient

    Please confirm on these queries points

    Thanks

    Abishek V

  • 0 in reply to Abishek V
    TI__Expert 6755 points

    Hi Abishek,

    1) The charger will enter a charge-recharge oscillation state. The voltage is dependent on your charge voltage and recharge threshold. From our FAQ page:

    • Will there be a problem if there's no battery connected to the output of the BQ25750 or BQ25756?
      There will not be a problem if the BQ25756 or BQ25750 is charging without a battery attached. The charger will charge the output capacitors, reach the charge voltage and then terminate. The capacitor voltage will then fall and reach the recharge threshold of the charger. At recharge, the charger will start the process over again.

    2) We have not tested the load transient with a battery disconnected.

    Best regards,
    Michael Bradbourne