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BQ24610: could resistor Rac be replaced by a 0R resistor or do not use a resistor?

user5147365
Prodigy 230 points
Part Number: BQ24610
Other Parts Discussed in Thread: BQ25790, BQ25713,

if my dc power is strong enough, could i do not use the Rac? use  a 0R or just cooper layout  in pcb? thank you.

  • 0
    TI__Mastermind 24075 points

    Hi,

      You can refer to this FAQ if you want to disable the input current regulation functionality: e2e.ti.com/.../791790

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    thank you. and i have another question, if i use a diode replace the 2 P-MOS and short ACN/ACP ,  under this situation ,  can the battery and dc power automatically switched when one is suddenly lost?

  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

       Battery and DC power switch based off of the FET controlled by BATDRV, and does not depend on the input reverse blocking FET or input current sense resistor.

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    please help to check the schematic attached 

    J1 input is DC power supply 12V, J5 is battery(3 x4.2v li battery series), J6 is power output, J6 should be powered by dc and the battery. the battery is always present as the backup power, when dc power lost,the battery power supply J6 automatically without power off.

    ,could it work normally and safely ?

    thank you very muck.

    BQ24610.pdf

  • 0 in reply to user5147365
    Prodigy 230 points

    in my circuit, BQ25610 how to judge current power source? whether the DC power supply, battery or both?

  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

       Your input is 12V, and your output is 3S Li-ion? This results in a 12.6V charge regulation voltage. BQ24610 is a buck charger, which means it needs input voltage higher than output voltage, so you cannot use this IC in your application. If you need a buck boost charger, please refer to BQ25713 or BQ25790/792

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    thank you! i have 2 dc power, 12v and 15v, if i use 15v dc power ,can my circuit work well?

  • 0 in reply to user5147365
    Prodigy 230 points

    and when i use 12v dc power, except can not charge the battery to 12.6v, will there be other problem? this is a old project, so i wish not change a new ic

    thank you.

  • 0 in reply to user5147365
    Prodigy 230 points

    I have an idea,when use 12v dc power， i can set the battery voltage to 11.1v through modify R242,R243 Value, because the battery is for backup，it can keep the system work for a short time is ok. is this feasible？

  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

       You have to account for voltage drop across cable, trace, RDSON etc. As long as VCC>VSRN by the SLEEP threshold specified in the datasheet, then converter will switch and everything will operate like normal. If you undercharge the battery, it will reduce run time but also extend battery life. I would check with battery manufacturer whether this is safe or not. 

    If your input is 15V, there is no issue. You can also look at the buck boost chargers if needed. Let me know if you have any questions.

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    Dear Kedar，

      I test my circuit in old board and encounter a problem, i first connect dc power and then connect the battery to the board, everything is ok, the indicator  led and the charge current is correct. but when i first connect the battery to the board and then connect the dc power, the indicator led will not be turned on and the charge current is abnormal, it seems the dc power directly  charge the battery, the higher  current with higher dc power,if i reconnect the dc power, the indicator led and the current is normal.  could you please help me to check the reason?thank you very much.

  • 0 in reply to user5147365
    Prodigy 230 points

    Hi,

     i found the reason, BATFET (Q25) is always on when connect the battery first, when dc power connect too, the batfet will not be turned off. what is the reason?

    i remove the Q25, The circuit seems  work well. can i remove Q25？ and what is the Q25 function?

  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

       BATFET is only on if you are in SLEEP mode. Verify you are not in SLEEP Mode. BATFET is used when there is an external system load in your system. If there isn't and you are just trying to charge the battery, then you can remove this PFET.

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    I have a li-battery as the backup power supply, and i remove the bat PMOS, when i disconnect dc power input, the battery can power the system through HIDRV NMOS without the battery PMOS, i seems no problem,

    Is there any hidden danger if doing so?
  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

       You will observe considerably increased thermal dissipation, as the efficiency loss from forward voltage drop of the HSFET body diode is much more than when the PMOS between BAT and SYS is conducting.

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    yes, i noticed that you mentioned, but i can not find the cause about how the high current come when connect a input source(12v or 15v) when Q25 and the battery is present. can you help me to check this? please find the attachment kindly ,thank you very much.7776.BQ24610.pdf

  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

        What high current are you referring to?

  • 0 in reply to Kedar Manishankar
    Prodigy 230 points

    quote the content before as below.

    if i connect the dc power fist then connect battery, the current is normal. .can you help me to check the cause about the high current under the situationi when first connect the battery then connect dc power, i found Q25 is always on when connect the battery first,and when i connect the dc power after connect the battery Q25 is still on,so i think the dc power supply directly connect the battery through Q25 and high current occurs. i do not know why Q25 is always on when connect the battery first,can you help me about this ? thank you.

    • In reply to Kedar Manishankar:

      Dear Kedar，

        I test my circuit in old board and encounter a problem, i first connect dc power and then connect the battery to the board, everything is ok, the indicator  led and the charge current is correct. but when i first connect the battery to the board and then connect the dc power, the indicator led will not be turned on and the charge current is abnormal, it seems the dc power directly  charge the battery, the higher  current with higher dc power,if i reconnect the dc power, the indicator led and the current is normal.  could you please help me to check the reason?thank you very much.

    • 200
      user5147365

      In reply to user5147365:

      Hi,

       i found the reason, BATFET (Q25) is always on when connect the battery first, when dc power connect too, the batfet will not be turned off. what is the reason?

      i remove the Q25, The circuit seems  work well. can i remove Q25？ and what is the Q25 function?

  • 0 in reply to user5147365
    Prodigy 230 points

    and when i first connect the battery then connect dc power supply, VREF is always 0v . why? even when i remove the battery and keep the dc power connected VREF is still 0v. but if connect the dc power fist,vref is 3.3v,and then connect the battery batfet is off,the circuit works well .

  • 0 in reply to user5147365
    Prodigy 230 points

    when i remove R57, the circuit works well,

  • 0 in reply to user5147365
    TI__Mastermind 24075 points

    Hi,

       What is R57 in your system? The FET driven by BATDRV is to connect SYS to BAT when there is no valid input voltage. This allows the system to still be powered by battery when adapter is removed. When adapter is present, SYS is powered by input, provided the input source is valid. You have to make sure input voltage is higher than output voltage by the SLEEP threshold delta. This behavior is described in system power selector section of the datasheet.