The value of the shunt resistor (RSHUNT) is selected such that the transient peak input current to the DC/DC converter (10 A) produces a voltage drop across the shunt resistor that matches the linear full-scale input range of the AMC1400-Q1 (250 mV). Consider the following two restrictions when selecting the value of the shunt resistor:

• The voltage drop across the shunt caused by the nominal-rated DC link current range must not exceed the recommended differential input voltage range for a linear response: |V_SHUNT| ≤ |V_FSR|
• The voltage drop caused by the maximum allowed overcurrent must not exceed the input voltage that causes a clipping output: |V_SHUNT| ≤ |V_Clipping|

In this example, a 25-mΩ shunt resistor is selected (RSHUNT = 250 mV / 10 A).

At the nominal-rated current, the power dissipation in the shunt resistor is R × I² = 25 mΩ × (4 A)² = 0.4 W. For surface-mounted shunts, the heat is mainly dissipated via the device terminals and the printed circuit board (PCB) traces. The power rating of a shunt is typically specified for a 70°C terminal temperature and derated for higher temperatures. This rating ensures that the shunt itself does not exceed its specified maximum operating temperature at the rated power dissipation. Careful PCB design is required not to exceed the terminal temperature at the rated power dissipation. Using wide copper traces to spread the heat over a larger area of the PCB, heat sinks, and air flow can improve the thermal design.