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This Film Decoupling Capacitor Using Non-Isolated Protective Diodes

IP.com Disclosure Number: IPCOM000049346D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Feinberg, I: AUTHOR [+2]

Abstract

A composite dielectric thin film capacitor, utilizing non-isolated overvoltage protection diodes on a silicon substrate, is used as an on-module decoupling capacitor for power supplies. The purpose of the capacitor is to provide s local switching current source for fast switching logic circuits. One requirement of the decoupling capacitor is that it contain four separate capacitors with one common electrode.

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This Film Decoupling Capacitor Using Non-Isolated Protective Diodes

A composite dielectric thin film capacitor, utilizing non-isolated overvoltage protection diodes on a silicon substrate, is used as an on-module decoupling capacitor for power supplies. The purpose of the capacitor is to provide s local switching current source for fast switching logic circuits. One requirement of the decoupling capacitor is that it contain four separate capacitors with one common electrode.

Like all other thin film capacitors, a diode across the capacitor is generally used to prevent damage to the capacitor by electrostatic discharge during handling in fabrication and testing.

Conventionally, four diodes are connected in accordance with the polarities of the power supplies to protect the four capacitors. In Fig. 1, V(1) and V(3) are positive, V(2) and V(4) are negative. When connected, the diodes D(1) and D(2) must be electrically isolated from each other. However, the process to fabricate isolated diodes is quite elaborate compared to non-isolated ones.

A novel scheme to connect two non-isolated diodes for capacitor protection is shown in Fig. 2.

Diode D(1) is connected between point 1 and point 2. Since V(12) (V(1)- V(2)) is positive. D(1) is reverse biased, as it is connected to the power supply. Another diode D(1) is connected between point 2 and common.

Now if a positive electrostatic potential is applied between point 1 and common, diode D(1) will break down and diode D(2)...