Calculate the current-sense resistance based on a maximum peak current capability of at least 20% higher than the peak inductor current at full load to provide sufficient margin during start-up and load-on transients. Calculate the current sense resistances using Equation 36.
VCS(th) is the 73-mV current limit threshold.
Select a standard resistance value of 7 mΩ for both shunts. A 0508 footprint component with wide aspect ratio termination design provides 1-W power rating, low parasitic series inductance, and compact PCB layout. Carefully observe the Section 11.1 to make sure that noise and DC errors do not corrupt the differential current-sense voltages measured at [CS1, VOUT1] and [CS2, VOUT2].
Place the shunt resistor close to the inductor.
Use Kelvin-sense connections, and route the sense lines differentially from the shunt to the LM5143-Q1.
The CS-to-output propagation delay (related to the current limit comparator, internal logic and power MOSFET gate drivers) causes the peak current to increase above the calculated current limit threshold. For a total propagation delay of tCS-DELAY of 40 ns, use Equation 37 to calculate the worst-case peak inductor current with the output shorted.
Based on this result, select an inductor for each channel with saturation current greater than 12 A across the full operating temperature range.