INA220: Can we Add Resistor Divider at INA220 Vbus and VIN Pins If Common Mode Voltage > 26V?

Hello Wayne,

Thanks for reaching out on the forum.  We do not recommend a high-side implementation with voltage dividers to the VIN pins.  The reason is that there can potentially be a substantial variation in the sense voltage you are trying to measure.  This is illustrated in the figure below.  In these examples I chose 1k resistors with 1% tolerance (I used the extreme values for emphasis, while in reality the difference between any two of the resistors could be alot smaller).  I chose 1k to avoid burning too much current or power.  I also avoided larger values as 1% tolerance for those can lead to a substantially larger difference between resistors and also to ensure that INA220's input impedance would not substantially contribute to the voltage divider.  From these circuits below, you can see that there are at least two general situations that yield a negative differential when there is a forward current.

As for a low-side implementation, that is possible.  However a few things you need to consider when using a voltage divider for the VBus pin with the low-side implementation.  I actually cover those in this thread here.

Hello Wayne,

this thread illustrates your options. The bus impedance of the INA220 is 320kohm.  Thus for the most accurate bus voltage measurement assuming you were dividing the real bus voltage in half, would be to use  3.2kohm resistors.  However, you we will need to calibrate your total current measurement to account for all the current passing through this divider.

Hello Wayne,

The bus pin impedance has a 15% tolerance.  Consequently, its impedance can range from 272kohm to 368kohm.  I am not sure exactly how you were going to set up the divider, but in two of the cases below, the voltage to the bus pin still exceeds 26V.  So, only the two configurations on the right are usable.  However, these configurations will definitely require some post processing to know the proper bust voltage.  Also, your customer will need to remember that the lower leg resistor in the divider will cause more current to be drawn and effectively raise the system load.