To start the procedure, the RSNS,
RDSON_NFET and wire resistance RWIRE, must be known.
- Determine RSNS to achieve 50 mV at
full current. For 3.3 A (3-A Type-C load current plus approximately 10% for overcurrent
threshold). RSNS = (0.05 V / 3.3 A) = 15 mΩ.
- RDSON_NFET = 50 mΩ
- RWIRE = 200 mΩ
- ΔVOUT = (RSNS + RDSON_NFET + RWIRE) × IBUS = (0.015 + 0.05 + 0.2) × 3 = 0.795 V
- Choose RSET = 300 Ω
- RIMON = (ΔVOUT × RSET × 2) /
(IBUS × RSNS) = (0.795 × 300
× 2) / (3 × 0.015) = 10.6
kΩ