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bq24616 / Minimum precharge current

S.Satoshi
Guru 21685 points

Hi Everyone,

Please let me ask about recommended minimum precharge current. Our customer want to set IPRECH to 50mA so I tired to evaluate by using EVM. As the result the measured precharge current was around 100mA though 50mV is applied on VISET2. Next I tried to set IPRECH to 160mA and 300mA, then I could see desired current.

So I guess that 50mA of IPRECH is lower than recommended range. Is my understanding correct?

Here is measurement result

  • VISET2 = 50mV (R16=1.56k) -> measured IPRECH = 104mA
  • VISET2 = 159mV (R16=5.1k) -> measured IPRECH = 140mA
  • VISET2 = 298mV (R16=10k) -> measured IPRECH = 278mA

Your comment will be appreciated.

Best Regards,

Sonoki / Japan Disty

  • 0
    TI__Expert 5565 points

    The minimum pre-charge and termination current is 125mA for the device. See paragraph below equation (5) in the datasheet (page 17):

  • 0 in reply to Smriti B
    Guru 21685 points
    Hi Bhuyan,

    I understand that the recommended minimum precharge and termination current should be 125mA.

    But in case ot VISET2 = 50mV (R16=1.56k), the charging was terminated at around 50mA though IPRECH is clamped. So this means that the termination current can be set lower than 125mA. Now our customer want to set termination current as low as possible, so please let me know if you have any concern for setting termination current lower than 125mA.

    I understand that the recommended minimum current is 125mA for both IPRECH and ITERM, so the accuracy can not be guaranteed at lower setting than 125mA.


    Best Regards,
    Sonoki
  • 0 in reply to S.Satoshi
    TI__Expert 5565 points
    Satoshi-san,

    Is the customer using a 10mOhm SRP/SRN sense resistor when measuring 50mA termination current?
  • 0 in reply to Smriti B
    Guru 21685 points

    Hi Bhuyan,

    Yes, they are using 10mohm Rsns and can see 50mA termination current.

    Best Regards,

    Sonoki

  • 0 in reply to S.Satoshi
    Guru 21685 points
    Hi Bhuyan,

    Our customer need to fix their schematic within this week, so I'm waiting for your comment.
    Again I need to know the concern when the IPRECH and ITERM are set lower than 125mA with 10mohm Rsns. I guess that the concern will be...

    - IPRECH will be clamped around 125mA but the accuracy can not be guaranteed.
    - ITERM can be set lower than 125mA but the accuracy can not be guaranteed.


    Best Regards,
    Sonoki
  • 0 in reply to S.Satoshi
    TI__Expert 5565 points

    Satoshi-san,

    I have confirmed that the termination current can be lower than 125mA, so the 50mA that the customer is observing is feasible. But as you pointed out, we cannot guarantee the pre-charge current and termination current lower than 150mA (with a 10mOhm sense resistor).