R_ILIM is used in setting up the active current sharing threshold during steady-state and the overcurrent limit during start-up among the devices in a parallel chain. Each device continuously monitors the current flowing through (I_DEVICE) and outputs a proportional analog output current on the ILIM pin. This, in turn, produces a proportional voltage (V_ILIM) across the respective ILIM pin resistor (R_ILIM), which is expressed as Equation 11.

G_ILIM is the current monitor gain (I_ILIM : I_DEVICE), with a typical value of 18.18μA/A.

• Active current sharing during steady-state: This mechanism operates only after the device reaches steady-state and acts independently by comparing the load current information (V_ILIM) with the Active Current Sharing reference (CLREF_LIN) threshold, defined as Equation 12.
  Equation 12. ${\mathrm{C}\mathrm{L}\mathrm{R}\mathrm{E}\mathrm{F}}_{\mathrm{L}\mathrm{I}\mathrm{N}}=\frac{1.1\times {\mathrm{V}}_{\mathrm{I}\mathrm{R}\mathrm{E}\mathrm{F}}}{3}$
  Therefore, R_ILIM must be calculated using Equation 13 to define the active current sharing threshold as I_OCP(TOTAL) / N, where N is the number of devices in parallel. Using N = 6, R_IMON = 167Ω, and Equation 13, R_ILIM can be calculated to be 367.4Ω. The closest standard value of 365Ω with 0.1% tolerance and power rating of 100mW resistances are selected as R_ILIM for each device.
  Equation 13. ${\mathrm{R}}_{\mathrm{I}\mathrm{L}\mathrm{I}\mathrm{M}}=\frac{1.1\times \mathrm{N}\times {\mathrm{R}}_{\mathrm{I}\mathrm{M}\mathrm{O}\mathrm{N}}}{3}$
  Note:

  To determine the value of R_ILIM, Equation 14 must be used if a different threshold for active current sharing (I_LIM(ACS)) than I_OCP / N is desired.

  Equation 14. ${\mathrm{R}}_{\mathrm{I}\mathrm{L}\mathrm{I}\mathrm{M}}=\frac{1.1\times {\mathrm{V}}_{\mathrm{I}\mathrm{R}\mathrm{E}\mathrm{F}}}{3\times {\mathrm{G}}_{\mathrm{I}\mathrm{L}\mathrm{I}\mathrm{M}}\times {\mathrm{I}}_{\mathrm{L}\mathrm{I}\mathrm{M}\left(\mathrm{A}\mathrm{C}\mathrm{S}\right)}}$

  When computing the current limit threshold during start-up in the next subsection, be sure to use this R_ILIM value.

• overcurrent limit during start-up: During inrush, the overcurrent condition for each device is detected by comparing the load current information (V_ILIM) with a scaled reference voltage as depicted in Equation 15.
  Equation 15. ${\mathrm{C}\mathrm{L}\mathrm{R}\mathrm{E}\mathrm{F}}_{\mathrm{S}\mathrm{A}\mathrm{T}}=\frac{0.7\times {\mathrm{V}}_{\mathrm{I}\mathrm{R}\mathrm{E}\mathrm{F}}}{3}$
  The current limit threshold during start-up can be calculated using Equation 16.
  Equation 16. ${\mathrm{I}}_{\mathrm{I}\mathrm{L}\mathrm{I}\mathrm{M}\left(\mathrm{S}\mathrm{t}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{u}\mathrm{p}\right)}=\frac{{\mathrm{C}\mathrm{L}\mathrm{R}\mathrm{E}\mathrm{F}}_{\mathrm{S}\mathrm{A}\mathrm{T}}}{{\mathrm{G}}_{\mathrm{I}\mathrm{L}\mathrm{I}\mathrm{M}}\times {\mathrm{R}}_{\mathrm{I}\mathrm{L}\mathrm{I}\mathrm{M}}}$
  By using a R_ILIM value of 365Ω for each device, the start-up current is limited to about 35A for each device and the I_LIM(ACS) is set at about 55A.
  Note: The active current limit block employs a fold-back mechanism during start-up based on V_OUT. When V_OUT is below the fold-back threshold (V_FB) of 1.99V, the current limit threshold is further lowered.