SLLSFO4C December 2022 – September 2023 ISOM8710 , ISOM8711
PRODMIX
The input side of ISOM871x is current-driven. To limit the amount of current flowing into the AN pin, it is recommended that a series resistor, RIN, is used in series with the input as shown in Figure 10-1.
RIN can be sized to minimize current flow and power consumption through the ISOM871x input-side, or it can be sized to enable higher data rates, depending on the application requirements. Regardless of the requirements, RIN should be a value that will limit the input forward current to be within the Recommended Operating Conditions for ISOM871x. The equation to calculate RIN for a given input voltage, VIN, and desired input forward current, IF, is shown in Equation 1 where VF is the maximum spec for the ISOM871x input forward voltage:
For example, with a 24-V input and 10-mA desired IF, RIN can be calculated as: