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BQ25120A: BQ25120A Please clarify, what happens when the voltage in falls below VIN(DPM) (ranging from 4.2V to 4.9V). Does charging stop? Does charging slow down?

Todd Keppler
Prodigy 180 points
Part Number: BQ25120A
Other Parts Discussed in Thread: BQ25120,

I need your help in understanding this paragraph of the BQ25120 datasheet.

 

Section 9.3.6 reads:

 

9.3.6 Input Voltage Based Dynamic Power Management (VIN(DPM))

 

During the normal charging process, if the input power source is not able to support the programmed or default charging current and System load, the supply voltage decreases. Once the supply approaches VIN(DPM), the input DPM current and voltage loops will reduce the input current through the blocking FETs, to prevent the further drop of the supply. The VIN(DPM) threshold is programmable through the I2C register from 4.2 V to 4.9 V in 100-mV steps. It can be disabled completely as well. When the device enters this mode, the charge current may be lower than the set value and the VINDPM_STAT bit is set. If the 2X timer is set, the safety timer is extended while VIN(DPM) is active. Additionally, termination is disabled. Note that in a condition where the battery is connected while VUVLO<VIN < VIN(DPM), the VINDPM loop will prevent the battery from being charged and PMID will be powered from BAT.

 

I am not quite sure how to interpret this. In the second to last sentence it says "Additionally, termination is disabled."  What does that mean?

 

Please  clarify, what happens when the voltage in falls below VIN(DPM) (ranging from 4.2V to 4.9V). Does charging stop? Does charging slow down?

 

Is there a risk to the battery if termination is disabled?

  • 0
    TI__Genius 12475 points
    Todd,

    I would recommend you to take a glance at this app note that explains VINDPM in detail.

    www.ti.com/.../slyt569.pdf


    The BQ25120A has a configurable VINDPM. Depending on the VINDPM setting, the current extracted from the VIN side could be limited. This is a safety feature to prevent brownout on the VIN side.

    This feature can be completely disabled as well on the BQ25120A.


    Regards,
    Gautham
  • 0 in reply to Gautham
    Prodigy 180 points
    None of my questions were answered from this article. I understand what VINDPM is.

    I am not quite sure how to interpret this. In the second to last sentence it says "Additionally, termination is disabled." What does that mean? (this was not discussed in the article)

    Please clarify, what happens when the voltage in falls below VIN(DPM) (ranging from 4.2V to 4.9V). Does charging stop? Does charging slow down? (This was discussed in general terms for TI chargers).

    Is there a risk to the battery if termination is disabled? (Not discussed. My concern is that the termination is disable and that the charger never gets to the constant voltage phase and over charges the battery.
  • 0 in reply to Todd Keppler
    TI__Genius 12475 points
    Todd,

    Termination occurs after entering the CV phase. The CV phase is held constant till the charge safety timer expires.

    Question 2 needs to be more clear- What is the VINDPM setting on question 2? If VINDPM loop is active on BQ25120A, then the input current will be limited.

    If input current is limited and not enough to supply the system on the PMID/ VSYS rails, charge current is throttled.

    If the current from input is not enough to supply the system then the current will actually be supplied by the battery.

    regards,
    gautham
  • 0 in reply to Gautham
    Prodigy 180 points

    So can you clarify what "termination disabled" means?

    I want to make sure I am not misinterpreting what this means.

    Todd Keppler

  • 0 in reply to Todd Keppler
    TI__Genius 12475 points

    Todd,

    It means that the BQ will hold in CV phase...

    Let me know if you want me to order you an EVM to test.