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bq24630 disabling Dynamic Power Management DPM

Maurice57272
Prodigy 50 points
Other Parts Discussed in Thread: BQ24630, BQ24620

Hi there,

I need to build a LiPo4 charger using the bq24630 chip.

I don't need the DPM, but I can't switch to bq24620.

I'd like to know in which way I can avoid to insert the DPM components (Q1, Q2, RAC, R17 & R18 ref. http://www.ti.com/lit/gpn/bq24630 pdf pg.2)

Particularly to which voltage should have I to set ACN, ACP and ACSET pins?

 

thank you

Maurice

  • 0
    TI__Guru**** 150930 points

    The components needed for input current DPM are RAC, C2, C3, R3, and R4.  Q1, Q2, R17, R14, R18, and C4 are needed to disconnect the adaptor terminal from the system/battery when the adaptor is removed and Q2 provides a controlled dI/dt to the system when the adaptor is plugged in.  Q1 and Q2 also provide a means to reduce the input current, but this is not their only function.

    To disable input current DPM, remove RAC, C2, C3, R3, and R4.  Connect the system voltage to the ACN and ACP inputs.  This imitates zero current through the sense resistor (which is no longer present).  Then, tie ACSET to VREF.  This tells the IC to begin reducing the input current when the (zero) current through the sense resistor rises above 3.3V (which it will never do).

  • 0
    TI__Guru**** 166996 points

    Q1, Q2 and their related components are present to prevent battery discharge back to the input supply and so are recommended. 

    What is the power rating of your input supply?  If you are 100% confident that it is capable of supplying enough current to both the system and for charging the battery, then we can change the connection points for ACN, ACP and/or ACSET to disable DPM.

  • 0 in reply to Chris Glaser
    Prodigy 50 points

    Hi Chris,

    if I want to remove the DPM and reduce the component list can I do as follows?

    1) substitute RAC with a short circuit

    2) remove C2, C3, R3, and R4

    3) connect the ACN and ACP inputs to Vcc pin of the IC

    4) tie ACSET to VREF

    5) eventually add a diode MBRS540T3 in series to the adapter as in bq24620 schematic to avoid battery discharging

     

    thanx again,

    Maurice

  • 0 in reply to Maurice57272
    TI__Guru**** 150930 points

    Yes, I believe that would be ok.  Vcc would need to be connected to SYSTEM for question 3 to work.

    Question 5 would need to be evaluated.  The bq24630, unlike the bq24620,  supports a power path--the system can be connected directly to the adaptor.  The FETs, Q1 and Q2 that your diode would replace, are able to be controlled in their turn on by the bq24630.  This reduces the inrush current that would flow if the system were connected directly and immediately to the adaptor when the adaptor is plugged in.  Just be aware that there will be a lot of inrush current and a large voltage spike when the adaptor is hot-plugged without Q1 and Q2.

  • 0 in reply to Chris Glaser
    Prodigy 50 points

    Hi Chris...

    I've a bq24630 EVM and I'm trying to start up using the EVM.

    I'm using a 4 cell battery pack and I changed R2 to 700K as in bqstroller calculation tools_V1.4 to adapt the out voltage.

    Then I have left TS connector open (without applying PS#2)

    Then I just would need to charge the battery pack from AC adapter, without having the system connected.

    In which way can I enable the charging of the battery pack without having the system connected?

    Thank you in advance

    Maurice

  • 0 in reply to Maurice57272
    TI__Guru**** 150930 points

    Maurice,

    As the EVM is setup, the TS pin is biased to 75.5% of Vref.  This will appear as a cold temperature fault and there will be no charging.  You must apply a voltage on that pin to bring its voltage in the range necessary for charging or attach a 10k resistor/thermistor from TS to ground.

    You can charge the battery with no system connected.  Simply follow the instructions in the user's guide for setting the jumpers.