CIRCUIT TO LIMIT DESENSE FROM CMOS DIGITAL ICS
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Aug-28
Desense (receiver interference caused by digital circuit noise) is becoming a greater problem as pagers shrink in physical size and digital circuits move closer to the antenna. (The microprocessor is not more than 1 cm away from the antenna in many modem pager designs.) A major cause of desense is the crowbar, or "shoot-through" current that occurs in digital CMOS gates as they switch. These short, high-amplitude current pulses appear at the IC Vdd and Vss pins, from where they may travel down supply lines, forming current loops that inductively couple into the antenna or other receiver circuits.