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# AMC1106M05: configuration of shunt resistor

Part Number: AMC1106M05

Hello Team, my customer needs support on shunt resistor configuration

Target is to achieve a measurement range of +/-350A-p (referred to +/-64mV). Shunt selection is difficult because only certain standard values are available. (100/200/300/500uOhm).

For this purpose a 180uOhm would be a perfect fit but preferred is 200uOhm (simpler available). But this means using a voltage divider of 10/90 ratio in front of the input stage.

Now the question:

- In the datasheet there is an input resistor of 4.9kOhm specified. Can this one be used with a 270 Ohm resistor on each input (560Ohm total)?

- Is the accuracy/tolerance of this 4.9kOhm in range of <1%?

- Or is it better to put 560 Ohm at AINP and AINN on GND?

- Other solution would be with a real voltage divider such as 1+20+1 Ohm and connect 20 Ohm at AINP/N?

Many Thanks for any proposal or other ideas to simplify the shunt resistor selection

Josef

• Hi Josef,

The AMC1106M05 is a +/-50mV input device, meaning that the specified input voltage range is +/-50mV, but as you pointed out, the clipping voltage is +/-64mV. As per the first link below, we typically recommend not going beyond +/-56mV to ensure a high accuracy measurement, as you risk approaching a nonlinear region. If the accuracy requirements are relaxed at the higher amperages, then this is less of a concern.

https://www.ti.com/lit/an/slyt810/slyt810.pdf

The 4.9kohm differential input resistance is the equivalent resistance of the differential amplifier and common-mode diagnostics circuits on the front end. As per the FAQ link below, this differential input impedance can typically vary +/-5% with 3-σ and 4-σ variations of +/-15% and +/-20% respectively, but there are not min/max specified values for these parameters and variations greater than these levels are possible. Therefor, it is best to treat this as a high input impedance input - which it is when compared to a 200uohm shunt.