When programming the output above unity gain (V_KA=V_REF), TL1431 is susceptible to other errors that may effect the overall accuracy beyond V_REF. These errors include:

• R1 and R2 accuracies
• V_I(dev) – Change in reference voltage over temperature
• ΔV_REF / ΔV_KA – Change in reference voltage to the change in cathode voltage
• |z_KA| – Dynamic impedance, causing a change in cathode voltage with cathode current

Worst case cathode voltage can be determined taking all of the variables in to account.