U1xy is the TMCS1108 isolated current-sense amplifier. Eight segments are supplied within the TMCS1108EVM board. Each segment is populated with one of the available device gains for bidirectional or unidirectional sensing. This configuration enables users to test the devices and determine the best gain setting for a given application. For y = A to D, the gain is 50 mV/A, 100 mV/A, 200 mV/A, and 400 mV/A, respectively.

• The TMCS1108AnB is used for bidirectional applications, while TMCS1108AnU is used for unidirectional applications (where n = 1 to 4 for the A1 to A4 gain variants, respectively).
• A magnetic field is generated based on the load current that is connected across the inputs IN+ and IN–, and flows through the TMCS1108 leadframe.
• The output voltage swing limitation and required load current sensing range are the key factors when determining device selection.
• The selected device must allow the output voltage to remain within the acceptable range after the load current is transduced and amplified by the respective device gain. The max output voltage must remain within the range of 25 mV above ground to 100 mV below the supply voltage.
• Choose an appropriate gain to create the largest appropriate output swing, and to minimize error.