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some questions about bq24600

Yang Li
Prodigy 40 points
Other Parts Discussed in Thread: BQ24620, BQ24600

hi,

I am working on a battery charger based on the BQ24600 with 4-cell Li-phosphate,and each battery is  3.2V/50Ah. Later i kow the BQ24620, but there is external circuit with MCU and ADC components to monitor and protect the battery,so it doesn't matter to use the bq24600 or the bq24620.

Input voltage: 24VDC

In the time earlier i tested the bq24600 in a PCB board with bad layout, but it works well except the heat conduction.So i used the same circuit and the same components in the new board,but it can not work.

The output voltage is just only 0.8V, and the state led  blink.

 So i get the waveform on the high side driver and the low side driver. i found they were always been turned off.

The VREF pin is 3.269V,  CE connect to the VREF,   S pin is 1.6V,  ISET pin is 1V.  REGN pin is 6V, and the bootstrap capacitor is 4.62V,

Because the output voltage is almost 0,the VFB pin is almost 0.

Then  I disconnect the HIDRV pin to the gate of high side MOSFET, both high side driver and low side driver output nothing.

 I replaced the bq24600 and the mosfet(SIR426) , nothing changed.  I need some suggestions

 

Thank you.

Lee

 

  • 0
    TI__Mastermind 32400 points

    Hi Yang,

     

    It looks like all the voltages are in the right levels. When the stat pin blinks means the battery is not detected. What is the battery terminal voltage before the battery is connected to the IC?  Does the battery detection routine is applied as described in the datasheet on page 19?  8mA/125mA discharge current should be applied for 1s/0.5s period of time.

     

    Thanks

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 40 points

    Hi Tahar,

    If don't connect the battery to the IC,the output is just 0.8V.

    I use a multimeter to measure the current between  battery and  SRN pin, it 's just  several μA. I guess the 8mA current source don't work.

    And sometimes the state LED is off.

    The IC seems to be in the sleep mode all the time,.

    I test  5 chips,  and have the same result.

     

    Thanks

  • 0 in reply to Yang Li
    TI__Mastermind 32400 points

    Hi Pareek,

     

    Using a muti-meter is hard to detect if the IC is applying the battery detection routine, because it will be just pulses of 1/2 and 1sec. I suggest using the scope instead.  

     

    The bq24600 uses a SLEEP comparator to determine the source of power on the VCC pin, since VCC can be supplied either from the battery or the adapter. If the VCC voltage is less than the SRN voltage, bq24600 enters the SLEEP mode. Can you verify the voltage on both of these pins and confirm if that is the case?

     

    You said that the first board was working fine, what are the main differences between the 2 boards?

      

     

    Thanks!

    Tahar

  • 0 in reply to Tahar Allag
    TI__Mastermind 32400 points

    Hi Pareek,

     

    Any updates...

     

    Thanks

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 40 points

    Hi Tahar,

    As I said the first board was working fine,but unfortunately i made a mistake.I short the Vout to the GND careleely.so that board was broken.The IC's VFB pin shorts to the GND pin.But the high side driver and the low side driver can output waveforms,the high side driver nearly output 100% duty-cycle pulse.These was the different from the board that was no driver output.

    I see the bq24600 carefully,and notice that there are two terminals(beside the pins but not the pin,you can measure them by using multimeter)at each side of the chip.They connect to the  back pad.I remenber that i use the soldering iron and solder the chip side by side. And the chip i solder as that were all no driver output.

    So i replace the BQ24600 , solder it pin by pin, and do not touch the terminals.Now the circuit is working fine.It charge a  4-cell  battery by 5A charing current.

    I guess the static electricity made the chips broken.

    Thank you for your help.