By following similar design procedure as outlined in Detailed Design Procedure, the external component values are calculated as below:

• R_SNS = 500 μΩ

• R_SET = 100 Ω

• R_IWRN = 47 kΩ to set 50 A as overcurrent protection threshold

• R_ISCP = 1.4 kΩ to set 60 A as short-circuit protection threshold

• C_TMR = 68 nF to set 1 ms circuit breaker time

• R₁ and R₂ are selected as 470 kΩ and 24.9 kΩ respectively to set VIN undervoltage lockout threshold at 24 V

• R_IMON = 15 kΩ to limit maximum V_(IMON) voltage to 3.3 V at full-load current of 50 A

• To reduce conduction losses, IAUS300N08S5N012 MOSFET is selected. Two FETs are used in parallel for control and another two FETs are used in parallel for reverse current blocking

  • 80-V V_DS(MAX) and ±20-V V_GS(MAX)

  • R_DS(ON) is 1-mΩ typical at 10-V V_GS

  • Q_g of each MOSFET is 231 nC

• C_BST = (4 × Q_g) / 1 V = 1 μF

Selection of Pre-Charge Resistor

The value of pre-charge resistor must be selected to limit the inrush current to I_inrush as per Equation 23.

Equation 23.

The power rating of the pre-charge resistor is decided by the average power dissipation given by Equation 24.

Equation 24.

The peak power dissipation in the pre-charge resistor is given by Equation 25.

Equation 25.

Two 220-Ω, 1.5-W, 5% CRCW2512220RJNEGHP resistors are used in parallel to support both average and peak power dissipation.

TI suggests the designer to share the entire power dissipation profile of pre-charge resistor with the resistor manufacturer and get their recommendation.