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BQ24165 need confirmation

C
Expert 2065 points
Other Parts Discussed in Thread: BQ24165, BQ24160, BQ24072, BQ24075, BQ24030, BQ24031, LM3478, TPS61232, PMP9773, TPS61088

Hello, 

i am thinking to use BQ24165 for one of our design where we have a DC source of 5V needing to charge Lithium battery. The system has to be able to switch between battery power the system or DC source power the system based on if there is DC source present or not. 

I have spotted the BQ24165 but I am not fully sure the system can be powered by the battery as back up by switching automatically ornot. Does anyone can confirm this ?

I am also looking at reference design for this chip.

  • 0
    TI__Guru**** 153196 points

    Yes, the bq24165 has powerpath and will auto switch to 100% battery power when the input source is removed.  The EVM is a reference design.  

    Can I get a bit more info about your application like input sources expected, charging and load currents expected, why the bq24165 is your first choice?

  • 0 in reply to Jeff F
    Expert 2065 points

    Hi Jeff,


    The application is an automotive system (a kind of eCall let's say, there will be some GPS, GSM modules, a TIVA C, accelerometer, TF CARD and EEPROM) where the circuit will be power via a lead acide battery 9-36V, but if the main battery is not working anymore then we need to switch to a Lipo battery . I added a LM536033QPWPQ1 in between the lead acid battery and the circuit to make the transition between 9-36V to 5V (we also have a LM74610QDGKRQ1 for protection surge purpose). There is another LDO going from 5V to 3.8V (MIC29302) and we also have another LDO SGM2019-ADJ to go from 5V to 3.3V.

    I was wondering if I should better charge the battery lipo from 5V or from 3.3V using the BQ24165.

    I also saw there are potential candidate  (BQ24160 may be?) for this charger powerpath switch but I am unsure which one is best suited for our application. There are so many chip...

  • 0 in reply to C
    TI__Guru**** 153196 points

    You do not appear to need dual power inputs.  Also, bq24165 is not automotive qualified.  What is the capacity of the LiPo battery and what maximum charge current are you planning on using?  All of our chargers are buck converter based so will need at least 5V input source.  Most of our automotive qual'd chargers have -Q1 following the part number. 

  • 0 in reply to Jeff F
    Expert 2065 points
    the customer does'nt require automotive qualification however I am happy to ear some alternative you would propose. I take note of the 5V as input and indeed we don't need the double input of the USB.
    Battery capacity will probably between 500 and 1000mAH
  • 0 in reply to C
    TI__Guru**** 153196 points
    For such low charge current and single input, I suggest using a linear charger with power path like the bq24072 or one of its siblings.
  • 0 in reply to Jeff F
    Expert 2065 points

    I don't see any Q1 version of those one.

  • 0 in reply to C
    Expert 2065 points
    Does /PG is the output who indicate in which state we are (either powered by IN or by Battery ?) Can you confirm ?
    I have to light a LED via our host mcu based on the situation.
  • 0 in reply to C
    TI__Guru**** 153196 points

    /PG indicates whether or not a valid input source is attached.

    There is a Q1 version of bq24075: 

  • 0 in reply to Jeff F
    Expert 2065 points

    Thank you for the link.

    Can you help me to review the schematic in attachment which I have done based on the reference design I found on TI, I have some doubt that the output of the BQ 24165 is really delivering 5V in out or less, if less how much ?

    Your help is well appreciated. Thank you

    CAR_SYSTEM.pdf

  • 0 in reply to C
    TI__Guru**** 153196 points
    Schematic looks okay. USB and IN need 1uF caps as close as possible to IC pins. SYS needs at least 20uF total, with 10uF close to IC pin while the remainder can be distributed. I could not determine the resistance value of the ILIM resistor. It is typically sized so that the there is enough input current available for charging and system load.
  • 0 in reply to Jeff F
    Expert 2065 points
    Can you confirm the output is well 5V ?
  • 0 in reply to C
    TI__Guru**** 153196 points

    If the BATFET is on and a battery is attached, then SYS output will be VMINSYS = 3.7V or 3.5V for V(BAT) < 3.7V (3.5V if VINDPM or IINDPM are active) and then 4.33V typical for V(BAT) >  VMINSYS.

    If BATFET is off (charge disabled or termination or TS fault or no battery attached) then SYS = 4.33V.

  • 0 in reply to Jeff F
    Expert 2065 points

    Hello Jeff, 

    I have modified the design as requested. Please check if it is correct now.

    Regards

  • 0 in reply to C
    TI__Guru**** 153196 points

    The schematic looks good.

  • 0 in reply to Jeff F
    Expert 2065 points

    I need to output 5V as you can see on the schematic. What should I modify in the cicruit to achieve this ?

    CAR_SOS.pdf 

  • 0 in reply to C
    TI__Guru**** 153196 points
    You cannot output more than the 4.2V on SYS.
  • 0 in reply to Jeff F
    Expert 2065 points
    What about if the USB is pluge d in ?
  • 0 in reply to Jeff F
    Expert 2065 points
    I suppose I should use a buck boost converter in this case if I want to bring it back to 5V from the 4.2 -3.5V, correct ? Do you recommend any ?
  • 0 in reply to C
    TI__Guru**** 153196 points
    The charger can only buck down from its input source. The LiIon battery maximum charge votlage is 4.2V. You could add a low cost boost converter to SYS output. If your system and charge current and input voltage are low enough that thermal losses are not significant, you would use the bq24030, bq24031 or bq24032 dual input linear chargers. When 5V is applied to its USB input, the linear charge does into dropout and the output follows the input, less a slight resistive drop across the pass FET.
  • 0 in reply to Jeff F
    Expert 2065 points

    I think I have no choice than adding a boost converter downstream the BQ24165 as from what I understand this charger power path will never deliver more than 4.2V due to limitation of battery.

    I need to get 5V as I have another LDO downstream which supply a device in 3.8V with max burst 2A (and I don't want to remove it as the reference design of another chip is a bit critical so I prefer playing safe game on this one), and this LDO also supply another LDO in cascade who transform 3.8V into 3.3V for other chips on the board, so I estimate I need at least 2.5 to 3A on this downstream rail.

    Which boost converter would you recommend for this situation ? (to go from SYS varuation of 3.5V to 4.2 V from the battery to 5V regulated in SYS)? According to Webench I should use LM3478 to do this... Can you confirm this ?

  • 0 in reply to C
    TI__Guru**** 153196 points
    LM3478 is okay but it requires external FETs. TPS61232 has the FETs integrated and is a more compact solution.
  • 0 in reply to Jeff F
    Expert 2065 points

    TPS 61232 doesn't seems to deliver more than 2.1A.
    I have spotted the TPS61088 which seems tobe able to output 3A. I also found a reference design for this one PMP9773 who seems predesigned for 5V output while taking battery as input.


    I have copied the reference design and removed the LM, however I have two questions:

    1./ How do I plug the EN pin ? On VCC direct ?

    2./ In the design guide of TPS61088 it is recommended to use R2 of 56K ohm, and to adapt R1, which normally for 5V should be 176K Ohm based on my calculation. In the reference design they use 316K and 100K !!!?