I am working on a device to measure the current of a supply in real time. The purpose of this, is to help with software development of ultra-low power 'always on' devices to be more efficient. The biggest market for this currently is IoT.
I want to have both speed and accuracy from an amplifier and I have therefore discarded all of the purpose made current sense amplifiers as they don't provide sufficient bandwidth for my application.
The specifications required are as follows:
- The highest voltage supply to be measured will be +5V to 0V. and the maximum current will be 1A. I will most likely use a 50mohm shut resistor, giving the maximum differential voltage of 50mV. I would also like for it to be accurate to the 100'suA scale, meaning that the differential voltage accuracy needs to be < 10uV (although I may use a 0.1ohm resistor for the lower scale).
- I need a high bandwidth across the gain range as I plan to use a 500ksps ADC to digitize the analog voltage, although will most likely be using 100-150ksps.
- It needs to have very good common mode rejection ratio.
- It needs to have the voltage offset as low as possible to get the best accuracy.
- Adjustable gain is a must ideally from an external resistor, that I will drive from a digital Pot.
I have been looking at the AD8220 for a rail to rail inamp, or the AD8221 which appears to be a better device for me, but will require a dual supply to get the full swing.
Can anyone suggest any better suited iamps that I have missed, or do these 2 seem the best suited for this application?
Any support will be very much appreciated.
Many Thanks Ian.