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BQ24074:

Arie Gordon
Prodigy 30 points
Part Number: BQ24074

I'm using BQ24074 in my new project.

In time of assembling it I need to see the Battery current and then the Charging current by connecting the DMM (mA)

In Battery current position all is OK

When over to the Battery Charging - it was not stable at all (sometime it works and sometime not) .

All is OK when DMM  was removed and

Where is the problem?

Please see attached drawing

  • 0
    TI__Guru 71366 points
    The problem may be resistance in the current shunt inside the DMM, it will add resistance to the output path. This could trigger early termination of charge by increasing voltage at the BAT pin.
    Also could cause problems with Battery Detection routing that is run at start up see figure 32 and 33 in data sheet.
    Check what the voltage at BAT looks like with a scope.
  • 0 in reply to Bill Johns
    Prodigy 30 points

    Hello Bill,

    Thanks for your answer.

    I need  short test to check the Battery and then Charging current to be sure that device works well.

    Tried also to use HP34401A DMM with the same results.Battery current measurement works OK but Charger not works.

    Please che ck and advice

    My application Drawing Attached.

    BR,

    Arie

  • 0 in reply to Arie Gordon
    TI__Guru 71366 points

    Hi Arie

    The input current and battery current (no load on out) will be almost the same.  Is measurement of input current as proxi for output current an option?

    Sch looks OK.

    ILIM R5 -- 1.18K --- 1.3A input current limit

    TMR R4 -- 46.4k -- 6hr

    ITERM R3 -- 4.12k -- 110mA

    ISET R2 -- 1.13k 800mA fast charge current

    EN1=Low, EN2=HI -- Set by ILIM

    Checked the HP34401

    Shut for 3A/1A -- 100m ohm

    for 100mA / 10mA -- 5.1 ohms

    I would think 100m is ok but 5.1 ohms would be a problem.

  • 0 in reply to Bill Johns
    Prodigy 30 points
    Hello Bill,
    How I can measure Charging current in easy and fast way?
    Please advice,
    BR,
    Arie Gordon
  • 0 in reply to Arie Gordon
    TI__Guru 71366 points
    Hi Arie
    The voltage on ISET pin can be used monitor charge current, see section 9.3.5.1 of the data sheet.
    Also if system load is set to 0mA then input current and output current will be almost the same.