illustrated embodiment the pad voltage needs to be u2267 vddo v d for the diode 222 to turn on and clamp the pad voltage to prevent voltage overstresses for example if the diode v d 0 7v and vddo 3 6v then the pad voltage must be u2267 vddo v d or 3 6v 0 7v 4 3v for the diode 222 to turn on and clamp the pad voltage if pad 4 2v for example and vddo 3 6v then in this example the voltage across the diode pad u2212 vddo or 4 2v u2212 3 6v 0 6v however as this voltage across the diode is less than the diode threshold voltage the diode will not turn on and thus the clamping circuit in this example will not operate fig2 further illustrates one example of a known clamping device a diode 224 having a threshold voltage or v d of about 0 7v for example in the illustrated embodiment the pad voltage needs to be u2266 vss u2212 v d for the diode 224 to turn on and clamp the pad voltage to prevent voltage overstresses for example if the diode v d 0 7v and vss 0v then the pad voltage must be u2266 vss u2212 v d or u2212.