[FAQ] Are there any suggestions from TI on how to comply with the "Safety Limiting Values"?

There are 3 main ways to limit current into the device that can prevent damage to the isolation barrier in the event of a single side fault.

1. Method 1: Series resistor
   1. A resistor in series with the I/O or supply rail is commonly used to limit the current of high-voltage transients. However, care need to be taken to ensure that the resistor does not cause a large voltage drop at the supply pin. For example, the resistor can’t be so large that the VCC goes 10% below the expected voltages on the I/O's.
   2. For example, a DC current of 8.2 mA and a voltage drop of 500 mV would require 61-ohm series resistor.
2. Method 2: Power Zener
   1. In the event that the expected failure mode cannot be satisfied with a series resistor it is possible to use a Zener regulator (power Zener)
   2. Note that when a diode fails, the failure mode is unknown (it can either fail short or open) therefore it is important to ensure the diode is rated for the worst-case fault voltage.
3. Method 3: Active short detection
   1. Method 3 relies on the use of external short circuit detection circuitry to detect the short and shut off power order. The current or junction temperature must be sensed and cut off very rapidly in order to prevent overheating of the die. This may be implemented through a shunt resistor and current sensing circuit that should turn off the supply in a time to prevent the die from getting to 150C.