Ref pin 3 and 7 of IC INA241B3 is conncted to 0.613V reference voltage as shown in below image but the pin voltage is loading to value of 0.600V.
The 13mV loading is resulting in a significant current offset at 0A reading.
What is the reason for voltage loading on Ref pins despite their high input impedance?
Thanks in advance
The reference pins do not have a very high impedance; the input bias current (about 35 µA) also flows through them.
Figure 8-7 shows an easier way to divide an external reference voltage by two:
Thanks for the information but datasheet does not mention anywhere the bias current of REF pins . Please add in the next revision of datasheet. As per the calculation , the REF pins are consuming 6.25uA each of bias current to load the resistor divider point to 0.6V. Can i get any data/graph on how this bais current vary over temperature range ?
After simulating with INA241B3 SPICE model , the results are quite different from actual readings on prototype board.
On our PCB , the REF pins are consuming quite a lot compared to 3nA of simulation .
could it be an issue related to a specific part placed on our proto board ?
is there any data on actual measurement of REF pins bias current from your side ?
Hey Rohan,
There is an error in the Revision A of this model that was created when transitioning from Revision E1. Here is a comparison between the E1 and theoretical input circuit of REF pins which shows correct behavior. I have attached the simulation with E1 model so you can continue development. The differences between revision E1 and A are minimal.
I will immediately begin to fix this error and will post back with the updated model as soon as possible.
I sincerely apologize for the inconvenience.
Peter
