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BQ24650: BQ24650 EVM change resistance R6 and R15, EVM it`s cannot working

Lawrence He
Genius 3280 points
Part Number: BQ24650

Dear,

Our client use BQ24650 EVM-639, but we find the issue, if  R6  0.02 ohm change to 0.05ohm and R15 100K ohm change to 86.6k ohm

Input 12V, output charge 12v battery

JP1 EX

JP2 Enable

JP3 EX

JP4 Disable


but Voutput it`s cannot charge. have any idea for our reference.


If any, Please advise me.


Thanks,


Best regards,


Lawrence.

  • 0
    TI__Mastermind 20570 points

    The bq24650 uses buck topology, which means the input voltage has to be higher than the output voltage in order to have the converter start working. To begin charging, VCC must be higher than SRN by at least 500 mV (otherwise, the device will be in sleep mode). Please make sure the voltage at VCC is at least 500mV higher than voltage on SRN.

  • 0 in reply to Jing Zou
    Genius 3280 points

    Hi, Jing Zou

    We use BQ24650 EVM, but we want output current change to 1A.

    i saw have two option can change to 1A.

    1. Change L1(15uH) and Cout (10uF) and Sense Resistor 40m ohm

    2. change R6 ;  icharge=40mv/R6

    have other suggestion for our reference.

    if any, Please advise me.

    Thanks,

    Best regards,

    Lawrence.

  • 0 in reply to Lawrence He
    TI__Mastermind 20570 points

    Option 2 is included in option... R6 is sense resistor.

    The inductor value and output capacitor value you listed is the recommend value for optimal performance. 

    We suggest to go with option 1.

  • 0 in reply to Jing Zou
    Prodigy 20 points
    HI jing
    we try EVM Board Chenng R19 36k to 100k ohm , So Vout & Pgnd can work on Bettery .
    but DC power supply CC & CV Vol 14.5V , but CC & CV Alwayes not steady (CC RED LED )
    jp 2-3 internol ,JP2 Enable ,jp3 1-2 ,JP4 Enable
  • 0 in reply to masm lin
    TI__Mastermind 20570 points

    Not sure I understand your question...

    What is the purpose of changing R19 to 100kohm?

    what is the charge current? What is the current limit on your DC power supply? Can you provide waveform on input voltage, input current, output voltage and output current?

  • 0 in reply to Jing Zou
    Prodigy 20 points

    Dear   jing  

    Take my test files bq24650 EVM Board test no Charger.pdf

  • 0 in reply to masm lin
    TI__Mastermind 20570 points

    Please refer to the datasheet of the charging profile. I probably misunderstand your "CC/CV not steady" statement. What you are referring to is the power supply is not steady? 

    Please use the bq246xx calculation tool in the bq24650 tools and software folder for the resistor calculation.

    I do not think the changes you made in the pdf file corresponds to your charging requirement. The MPPT value you set gives you around 7.2V which is only 50% of our power supply output. From your picture, I cannot tell what the current limit you have set on your power supply. If you see your power supply is not steady, you might drawing more current than your power supply current limit. In result, the input voltage will droop. Since you have see the MPPT to 7.2V, the input voltage to the charge will then be clamped at 7.2V which is lower than the output voltage. Thus converter turned off, then your input voltage recovers. Therefore, you will see the power supply goes between CC and CV mode.

    Also as a note, VFB resistor divider will not give you 12V battery regulation voltage.