JAJSUF8A April 2024 – July 2024 ISOM8110-Q1
PRODUCTION DATA
The input side of ISOM811x-Q1 is current-driven. To limit the amount of current flowing into the AN pin, placing a series resistor, RIN, in series with the input as shown in Figure 9-1 is recommended.
Depending on how the ISOM811x-Q1 device is being used, the value of RIN can vary quite a bit. However, at a high level, to make sure the input does not get damaged, the minimum value of RIN can be calculated for a given input voltage, VIN, in Equation 3:
However, in the use case of a feedback loop, RIN directly affects the mid-band gain of the loop. Assuming that the TL431 has been configured to give a reference voltage, VREF, of 2.5V and RPULLUP is 5kΩ, Equation 4 is used to calculate the maximum value of RIN verifying that the VCOMP voltage on the primary side can be pulled to the saturation voltage of the ISOM811x-Q1, VCE(SAT).