A fixed 3.3-V output voltage device is used for this application. The MID_OUT voltage is set to 12 V by tying the V_MVSEL1 pin to GND and setting V_MVSEL2 to ≥ 0.9 V using the R3 and R4 resistor divider. The value of the R3 and R4 divider ratio must ensure that V_MVSEL2 is set to ≥ 0.9 V when V_IN ≥ 15 V. To limit the current burned through this divider to 5 μA, R3 can be calculated using Equation 10, and the calculated value then can be rounded to the nearest standard value. When V_IN goes all the way up to 85 V during a transient, the V_MSEL2 voltage goes up to 3.9 V (which is still lower than the maximum recommended value for this pin, as specified in the Section 6.3 table).

R4 then can be calculated with Equation 11 by using the VMVSEL2 value of the same current value.

The enable precision circuit is also used to turn off the device when V_IN drops below 15 V. The R1 and R2 resistor divider is used to set V_EN to lower than V_EN(LOW) of 1.15 V when V_IN drops below 15 V. R1 can be calculated using Equation 12 to limit the burned current through this divider to 5 μA, similar to the above divider.

Equation 13 can then be used to calculate R2. The calculated R1 and R2 values can then rounded to the nearest standard values.