APPLICATION-SPECIFIC CMOS OUTPUT DRIVER CIRCUIT-DESIGN TECHNIQUES TO REDUCE SIMULTANEOUS SWITCHING NOISE

Application specific CMOS circuit design techniques to reduce simultan eous switching noise (SSN-also known as Delta-I noise or ground bounce ) were analyzed. Detailed investigation on the CMOS output driver swit ching current components was performed. The limitations in using curre nt controlled (CC) CMOS output drivers in high-speed (> 30 MHz) design applications are explained. Application specific, high-speed, control led slew rate (CSR) CMOS output drivers were studied and designed. For a given device channel length, once the predriver and driver device s izes are fixed, the performance (speed, switching noise, sink/source c apabilities) is determined. With controlled slew rate output drivers, more than 50% improvement was found in the input receiver noise immuni ty (measure of maximum tolerable SSN) compared to conventional drivers , while the speed and sink/source capabilities are preserved. This eff ective SSN reduction improvement is achieved with only a small increas e in output driver silicon area. The CSR output driver uses distribute d and weighted switching driver segments to control the output driver' s slew rate for a given load capacitance. These CSR CMOS output driver s were compared with standard CMOS output drivers, showing significant reduction in effective switching noise pulse width.