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INA233: current measurement

user5949476
Prodigy 20 points
Part Number: INA233

Hello,

I try to drive INA233 by MCU. I wrote Init function where I set these registers:

1) CLEAR_FAULTS => 0

2) MFR_CALIBRATION => 1024 (0x400) (15A max on 5mOhm R)

3) MFR_ADC_CONFIG => ADC_AVG_16 (0x0400), VBUSCT_1100us (default 0x0100), VSHCT_1100us (default 0x0020), MODE_SH_BUS_CO (default 0x0007)

4) MFR_DEVICE_CONFIG => 0x02 (default)

Then I read voltage and curent each 500ms like this:

Voltage from register READ_VIN => ReadVaule * 125 / 100 => voltage in mV => it meas correctly / its OK.

Current from register INA233_READ_IIN => return always zero. (I tested cca 1A into 12Ohm load)

Then I found out that STATUS_WORD return MFR bit (manufacturer-specific fault or warning has occurred). Why?

What I forget or did wrong  and why current not measure correctly?

I read in datasheet this:

"Without setting the device register with the MFR_CALIBRATION command, the deviceis unable to provide either a valid current or power value because these outputs are both derived using the values loaded into the calibration register." But I set the callibration register in init function already.

Thank you for any advice.

Best regards

Tomas

  • 0
    TI__Mastermind 27390 points

    Hi Tomas,

    It appears proper configuration of INA233 is being followed. Here is what I would do to double check if the program is actually doing what you asked it to do.

    First make sure there is not a power cycle or software power on reset between initialization and current reads.

    Second, insert a configuration register read and shunt voltage register (D1h) read before or after current read. The purpose is to see if the configuration value sticks and if INA233 returns the correct shunt voltage (~5mV).

    Last but not least, check your PCB hardware to make sure INA233 indeed sees 5mV at its input.

    MFR bit is an OR-ed aggregation of all bits in register 80h. A number of things can flip it, therefore by itself it is not very informative. Concentrating on being able to read the shunt voltage and further shunt current should solve the issue.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Prodigy 20 points

    Hi Guang,

    Thank you very much for your advice. The issue was not in setup of INA233 it was in HW on PCB.

    One of the analog inputs of INA233 was not connected to the shunt resistor.

    After re-solder the input everything is OK and it meas correctly.

    Sorry for unnecessary alarm about current measurement fail of INA233.

    Regards, Tomas