Other Parts Discussed in Thread: INA197, INA190
Hi there, I'm considering the INA181 to perform bidirectional current measurements because of it's accuracy and simplicity. I'm measuring voltages across a 33mohm shunt and the common voltage will typically be around 8-16V. The device datasheet suggests transient protection consisting of a TVS and back-to-back diodes, however I was wondering if there was a simple way to protect the device from reverse polarisation as well.
The common mode input range is only -0.3 to 26V, so I would need to limit the voltage on the input pins to -0.3V somehow. This seems very difficult considering the requirement for a low impedance in the sense lines (<10ohm). The current would be too high for any diode to handle.
Am I missing a simple way to protect the device against reverse polarity on the input pins or will I not be able to use this device? If not, can you suggest another device with comparable accuracy? We've used the INA197 before, but accuracy is not as good (3%).
Here's a rough schematic of what our circuit looks like. The LM5050 is used as reverse polarity protection for INPUT 1, for INPUT / OUTPUT 2 we can't use that trick as it's an input as well as an output. There is reverse polarity protection to the internal system rail for both inputs via simple diode OR-ing, but there is nothing stopping the voltage at INPUT 2 getting below GND. Ideally the current monitor would be able to handle this (considered as a fault condition, so it doesn't have to be operational).
