Part Number: TL431B-Q1
Hi There,
My customer will be using the TL431-Q1 as a comparator in their design, something similar to the figure below:
Could you tell me what is the maximum allowed voltage on the REF pin please? Would it be 37V, even if the Cathode is powered from 12V?
Many thanks,
Ross
Hi Ross,
The Ref pin voltage is not specified on the datasheet but the current is. This is because if the voltage of the Ref pin is dependent on its current, and if the voltage is higher than its typical VRef the current consumption is extremely high and can violate its absolute maximum current. The 37V will violate the current limit of the device if it is not current limited. I would highly recommend inserting a series resistor on the VRef as this will limit the current going into the pin and make sure the maximum current is not violated.
For example, in the schematic below the current into the VRef_pin is limited by the RRef resistor. The size of this resistor is selected based off of the maximum voltage that the Vref pin will experience. In the graph below notice how as the voltage VREF_sup increases but the voltage at VREF_pin stays stable because the current is limited. The resistor was selected to make sure the VRef_pin has enough current to function and also that at the maximum voltage on the pin will not cause the pin to exceed its maximum current limit.
-Marcoo
