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INA210: sampling issues

Ethan Liu
Intellectual 1425 points
Part Number: INA210

Tool/software:

Hi team

Here comes a problem. Use INA210 to do high-side current sampling on the low-voltage 12V side.
The connection method is similar to this:

Disconnect the back stage of INA210 and test the Vout value.
When Rshunt is 0 current, the output is 0V. But when the current flowing through Rshunt reaches 1.3A, the output Vout suddenly rises to 5V.
When the current of Rshunt is 1.1A, the output Vout is still normal, basically close to 0V.
The waveform is as follows:

The green one is the Vout waveform. The first peak is when the machine is started; the second time it reaches 5V is after it is loaded with 1.3V.
The output voltage cannot drop any further.
Please help me look at this problem and tell us why, thank you

BR,

Ethan

  • 0
    TI__Expert 7995 points

    Hello Ethan,

    Can you please give me more information about how the device is connected? What is Vref connected to? What is the shunt size? Can you send a picture of the measurement setup?

    Thanks,

    Levi DV

  • 0 in reply to Levi DV
    TI__Intellectual 1425 points

    Hi Levi,

    The schematic is shown as below, and Rshunt = 0.1mohm with 2512 package. There is no load in the system, the positive side of shunt is connected to 12V supply, the negative side of shunt is connected to ground directly. V+ is 5V, REF is 0.5V.

    When Ishunt>=1.3A, Vout reach to 5V (Normally close to 0V); when Ishunt<1.3A, the Vout nearly 0V.

    Can you help analyze why Vout is abnormal when Ishunt>=1.3A?

    BR,

    Ethan

  • 0 in reply to Ethan Liu
    TI__Expert 7995 points

    Hello Ethan,

    Looking at this schematic the capacitors C10 and C46 should be removed. Common-mode filters like this should not be used without a differential-mode filter with a lower cutoff frequency.

    Can you show me the same plot as above with a current waveform or a measurement across the shunt resistor? Also showing the reference voltage would be helpful.

    Thanks,

    Levi DV