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INA226: About accuracy

Ozawa
Intellectual 850 points

Part Number: INA226

I have three questions.

◆No'1　:　I want to reduce error.◆

The following conditions are the measurement conditions.
 Measurement conditions ------------------------------------------
Temperature T_A [C]: -20 <= T_A <= + 70
Measured voltage V_SENSE [V]: +1 <= V_SENSE <= + 5
Power supply voltage V_S [V]: DC + 3.20 <= V_S <= + 3.40
-------------------------------------------------------------------- -----

The error (when measuring the voltage) was estimated from the table of datasheet p. 3 as follows.
Estimated error ------------------------------------------
Bus offset voltage error: 0.935 [%]
Bus voltage gain error: 0.325 [%]
Differential nonlinearity error: 0.013 [%]
Total: 1.273 [%]
@ (T_A = -20, +70 [C], V_SENS = +1 [V], V_S = DC + 3.20, +3.40 [V])
-------------------------------------------------------------------- -----------
The total error is 1.273 [%], but I want to keep the error within 1 [%].

Please tell me if there is a way to reduce the error.
(Items that can be compensated for temperature, items that can be corrected for each individual IC, other advice, etc)

◆No'2 : Please let me know the characteristics of the error.◆

The following error is written in data sheet p.3
--------------------------------------------------
Shunt offset voltage, RTI
Bus offset voltage, RTI
Shunt voltage gain error
Bus voltage gain error
--------------------------------------------------

Is the above error an error determined for each individual IC?
Or, does this error change with each measurement?

◆No'3 : Could you tell me the standard deviation of the next item shown in datasheet p.3?◆
--------------------------------------------------
Shunt offset voltage, RTI vs Power supply
Bus offset voltage, RTI vs Power supply
Differential nonlinearity
--------------------------------------------------

Best regards,

  • 0
    TI__Genius 14825 points

    Hello Ozawa,

    Regarding your questions about error sources, we have released a video series (link) that explains much of the errors that can happen in current sense amplifiers.  The videos talk about what the errors are, how to calculate them, and how to minimize them.

    Regarding your questions about the data sheet page 3: the data sheet on the web shows the pinout of the part on page 3, so I think we may be looking at different pages or different data sheets.

    There are two voltages that this part measures, a shunt voltage (across IN+ and IN-) and a bus voltage (across VBUS and GND).  The offset is the voltage seen when the inputs of the device are equal but the output is not 0.  For instance,  IN+ = IN-, the input voltage is 0.  However if the output measured is 2uV, then the offset voltage would be 2uV.  Same for when VBUS=GND.  Offset voltage is the dominant error source for small input voltages.

    The Gain error is how different the measured voltage is relative to the input voltage.  For instance, if we put VBUS=20V and measured 20.02V, then we would say the part likely has 0.1% gain error.  Gain error is a percent and so it is constant across inputs, so we would expect to see 10.01V with VBUS=10V as well, if the gain error of the part is 0.1%.  Gain error is the dominant error source of input voltages near full scale.

    Regarding distribution data, we cannot provide what is not already in the data sheet.