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INA226-Q1: Gain question

Part Number: INA226-Q1
Other Parts Discussed in Thread: INA225-Q1, INA237, INA238, INA228, INA234, INA236, INA232, INA4230, INA4235, INA223, INA190-Q1, INA225

Tool/software:

Hi team,

I want to know why most of our digital power monitors have only 1V/V gain.

My customer wants a digital power monitor with adjustable gain(INA225-Q1 with I2C). Do you have any recommendation?

Regards,

Peter

  • Hello Peter,

    Our digital power monitors do not have an analog output, so there is not a traditional gain, as results are read from a results register value. Some of our digital power monitors do have adjustable ADC range, which may be what you are looking for. Some of those devices include:

    INA228 family (INA228, INA238, INA237)

    INA236 family (INA236, INA234, INA232)

    INA4235 family (INA4235, INA4230)

    If you are looking for something with I2C programmable gain with an analog output, then you may be interested in the INA223.

    Regards,

    Mitch

  • Hi Mitch,

    I checked INA223. It cannot meet the requirement:

    1. Customer needs 40V common-mode voltage;

    2. Automotive version;

    Do we have any other promotion? Or we just need to focus on INA225-Q1?

    They use it to detect the current of LEDs, the voltage can rise to 36V.

    The minimum current is 5mA and the maximum current is 500mA.

    Their ADC can only accept 0-3V input so when the current is 5mA, the ADC voltage is only 0.03V. It is too small to detect.

    I selected INA225-Q1 as new promotion and they have to use 240m ohm is this case. 

    They wonder if 240m ohm Rsense has any risk.

    Regards,

    Peter

  • Hello Peter,

    The INA223 is our only analog out device with programmable gain....

    If they are not able to meet their accuracy requirements with the INA225 across the full measurement range, then they could switch to a more precise device, like the INA190-Q1. Or they could use two INA225's, one for high current and one for low current (using either two different shunts, or two different gain versions).

    Regards,

    Mitch

  • Hi Mitch,

    The problem is that their ADC cannot detect a low voltage like 30mV, so INA190-Q1 would not help.

    I think two INA would be too complicated. Customer will not consider a solution like this.

    Can you tell me if 240m ohm Rsense has any risk?

    I know the power consumption is larger. Is there any other risk?

    Regards,

    Peter 

  • Hey Peter,

    I do not see any risks with using that value for a shunt resistor. Here is a link to a calculator tool that can also help show error for a given setup: https://www.ti.com/tool/download/CS-AMPLIFIER-ERROR-TOOL 

    On a side note, if their ADC is not accurate enough, they could switch to a device like the INA228. This device has an integrated ADC and is very precise.

    Regards,

    Mitch