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# Current measurement from 15uA to 5mA from a 3.6V supply - INA216?

Other Parts Discussed in Thread: INA216

Hello,

I'm looking to find a device that can measure a current from 15uA to 5mA off of a 3.6V supply

I have been considering the INA216.  What is the value for the min and max for Vsense on the INA216?

http://www.ti.com/product/ina216a3

There is a chart on page 7 of the datasheet for which I would like to get some clarification on also.

Any feedback or suggestions are welcomed and appreciated.

Best regards,

Paul

• Hello Paul,

Thank you for your interest in the INA216 for your current sensing solution.  I will assume 3.6V is your common-mode voltage and that you're supplying the device with 5V.

The min and max values for Vsense of the INA216 will depend on the supply voltage.  That is because the supply voltage of the device sets the output voltage range.  Let's go through an example:

Say you select the INA216A1 (G=25V/V), and use a supply voltage of 5V.  According to the datasheet, the output of the device (worst-case) is 2mV to 4.7V (assuming a load of 10kohms).  Now we translate this output voltage to an input voltage (aka referred-to-input) by dividing by the gain (25V/V).  This equates to and input voltage range, or Vsense range, of 0.08mV to 188mV.

You did not list which figure on page 7 requires clarification.  Please let us know the figure number and your questions.

A little advice concerning your shunt resistor:  make it as large as possible.  This is to reduce inaccuracies caused by the input bias current.  For example, using a 36ohm sense resistor will yield a Vsense of 180mV when the load current is 5mA.  For 15uA load the sense voltage will be 0.54mV.  Figure 8 shows that a sense voltage of 0.54mV yields very little input bias current.  This is important because your're sensing only 15uA of current.  If your sense voltage was 0.1mV, according to Figure 8 the device could draw ~1uA of bias current, which would introduce 6.7% error in the measurement.  That would be in addition to error due to initial input offset voltage.  Assuming Vsense=0.54mV and an initial input offset voltage of 100uV, you already have 18.5% error in the measurement (100uV/540uV*100=18.5).