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BQ24600: Battery not get detect

Part Number: BQ24600

Hii ,

I am using bq24600 ic  for 4  cell lithium polymer battery charge but battery not get detect i set battery charge current 500mA,I observe voltage verf=3.3V,  CE=3.3V,

REGN=6V, but lower side FET not drive and SRP-SRN voltage is lower than 1.25 mV .whats the problem  please help.

Thanks and Regards

Anita 

  • Hi Anita,

    Please only post one thread for the problem you have.

    It would help a lot if you can send a schematic of your design along with the waveform on VCC, SRN and REGN using an oscilloscope.

    A charge current of 500mA would put the converter into non-sync mode, where the low side FET is turned off and only turns on for 80ns to refresh the bootstrap cap. You can read more about this on section 7.4.2 of the datasheet.

    If the SRN voltage is lower than 2V, then you could also get into this non-sync mode where low side FET is turned off.

    If you don't want non-sync mode, then your charge current would have to be higher than 500mA.

    Regards,
    Steven
  • Dear sir,

    Thanks or reply.

    My account showing  login banned whats the problem, so i am not able to reply i want help to login my account so i will share schematic and waveform  please help.i increase charge current to 1.5 A but also battery not detected and taking only 200 mA charge current

    battery charger.pdf

    Thanks & Regards

    Anita Kalbhor

  • Anita,

    I see there is a problem on the input filter, although I don't think it may be the cause of the problem, you should change R11 to 2ohm.

    I want to know what is the voltage on CE, VREF, REGN, TS, VCC and SRN, and also see if you can get a scope screenshot of VCC, PH, SRN and VFB to see if the conditions look good to start a charge cycle.

    Regards,
    Steven
  • Dear sir,

    Thanks  for replycharger pcb waveform.rarM501 V0 defib battery charger.pcb

    Voltage observe on  CE=3.6V ,     Vref=3.6V,          REGN=6V,      TS=1.65 V,   VCC=18.4,   SRN=15.6V

    and i have observe very large noise on PH,HIRDV,LIRDV,and BTST  pin  whats the issue please suggest  .

    also check attached waveform images and layout file.

    Thanks & Regards

    Anita Kalbhor

  • Anita,

    There is definitely some problem with the PH waveform. Please provide screenshots of PCB for each layer, preferably in PDF, as it would be much easier for me to see the layout file that way.

    I suggest you follow the layout like the following:

    Keep the loops very small and use wide traces to reduce parasitic inductance. Input caps as close as possible to HS fet and output caps as close as possible to sense resistor.

    You can also add an RC snubber on the PH node to reduce ringing.

    Regards,

    Steven

  • Dear sir,

    Please check attached pdf file of layout .i make layout as per datasheet in that sense resistor horizontal

    direction.

    Because of layout that much noise are coming or another reason . My circuit is not working still battery not get detect.i check 5 PCB  in that status Led blinking when battery is connected  in 4 pcb and in one pcb status led glowing continuously but taking only 30mA current. 

    I have set charge current 1.5A but also it taking olty 20 -30mA current .

    I dont get  voltage difference in  SRP-SRN pin both voltage showing same voltage level equal to battery voltage level.

    Thanks & Regards

    Anita KalbhorBatery charger Layout.rar

  • Anita,

    I see that the layout needs a lot of optimizing. Please follow what I posted before. Also, a few other pointers:
    1. Use as much copper pour as possible. This will help dissipate heat. Any empty spaces fill with GND.
    2. Look up Kelvin connection for SRP and SRN. You want direct connections to the sense resistor and no current passing through these traces.
    3. The filter caps like 0.1uF on the schematic are to be placed close to the IC as possible.
    4. Connect thermal pad of the IC directly to GND with lots of copper pour. Do not route using thin traces from thermal pad to GND. Use many vias.
    5. Do not route sensing lines like SRP and SRN, VREF, ISET and VFB close to switching nets, they might get coupled with noise and not work properly.

    Hope this helps on improving your layout.

    Regards,
    Steven