Depletion controlled isolation stage.

摘要

An input protection device is presented having a depletion controlled isolation stage. In one embodiment of the invention, a depletion controlled isolation resistor (10) is formed between adjacent N+ diffused regions (16 and 18) by N-well diffusion. One N+ diffused region (16) electrically contacts an input bond pad (20) and a primary protective device. The other N+ diffused region (18) electrically contacts a second protective device and the internal circuit (21) it is to protect. The depletion controlled isolation resistor limits the amount of current passing through the resistor to a safe level during an over-voltage condition. In another embodiment of the invention, a depletion controlled isolation stage includes a silicon controlled rectifier (SCR) as the primary protective device in combination with the depletion controlled isolation resistor. <IMAGE>