1. Find out the full-scale range of ISYS_IN pin in the VR14 controller.
2. Set the V_IREF of all the eFuse modules (U₁, U₂, U₃, ... , and U_N) (either a single TPS25984, TPS25985 or TPS25990 eFuse or a parallel combination of TPS25990 and TPS25984/5 eFuses for higher current designs) to half of the maximum voltage range of the ISYS_IN input of the VR14 controller. This provides the necessary headroom and dynamic range for the system to accurately monitor the load current up to the scalable fast-trip threshold (2 × I_OCP).
   Note: The value of V_IREF must be same for U₁, U₂, U₃, ... , and U_N.
3. Select the required circuit-breaker thresholds during steady-state (I_OCP-1, I_OCP-2, I_OCP-3, ... , and I_OCP-N) for all the eFuse modules. TI recommends selecting the circuit-breaker thresholds during steady-state as 1.1 to 1.2 times the maximum steady-state current or the thermal design current (TDC).
4. Calculate the value of R_IMON resistors (R_IMON-1, R_IMON-2, R_IMON-3, ... , and R_IMON-N) for all the eFuse modules using Equation 3 to set the desired over-current protection or circuit-breaker threshold as selected in the above step.
5. Let assume a constant positive number, k₁ for the eFuse module-1 (U₁). The corresponding factors, k₂, k₃, ... , and k_N for the eFuse module-2, 3, ... , and N (U₂, U₃, ... , and U_N) are defined as Equation 14.
   Equation 14. $k_2=k_1\frac{R_{IMON-1}}{R_{IMON-2}}$ , $k_3=k_1\frac{R_{IMON-1}}{R_{IMON-3}}$ , … , and $k_N=k_1\frac{R_{IMON-1}}{R_{IMON-N}}$
6. Let consider the value of R_IN-1 in Figure 6-2 as 50 kΩ. The values of the R_IN-2, R_IN-3, ... , and R_IN-N in Figure 6-2 need to be calculated using Equation 15.
   Equation 15. $R_{IN-2}=R_{IN-1}\frac{R_{IMON-2}}{R_{IMON-1}}$ , $R_{IN-3}=R_{IN-1}\frac{R_{IMON-3}}{R_{IMON-1}}$ , … , and $R_{IN-N}=R_{IN-1}\frac{R_{IMON-N}}{R_{IMON-1}}$
   Note:

   • Choose the value of R_IN-1 in such a way that the values of R_IN-2, R_IN-3, ... , and R_IN-N including R_IN-1 are in the range of 20 kΩ - 500 kΩ to maintain stability and adequate slew-rate of the operation amplifier.
   • The selected values of R_IN-1, R_IN-2, R_IN-3, ... , R_IN-N, R_IMON-1, R_IMON-2, R_IMON-3, ... , and R_IMON-N must be as close as possible to the calculated ones to get better accuracy. These resistances must have a tolerance of less than 0.1% and a power rating of more than 100 mW. For noise immunity, place a 22 pF ceramic capacitor from the IMON pin to GND in each eFuse module.
7. The values of m₁, m₂, m₃, ... , m_N in Equation 11 can be obtained using Equation 16.
   Equation 16. $m_1=k_1/\sum _{n=1}^N{k}_n$ , $m_2=k_2/\sum _{n=1}^N{k}_n$ , $m_3=k_3/\sum _{n=1}^N{k}_n$ , … , and $m_N=k_N/\sum _{n=1}^N{k}_n$
8. Finally, select the internal scaling factor ISYS_IN_GAIN (set through the SVID_CONFIG) according to Equation 13.

A non-inverting summing amplifier design example is presented in Figure 6-3. The IMON outputs from six (6) eFuse modules or PSYS monitors are added together to retrieve the total system current, drawn from the PSU.

Figure 6-3 Non-Inverting Summing Amplifier Design Example