A CMOS Off-Chip Driver/Receiver with Reduced Signal Swing and Reduced Power-Supply Disturbance

A CMOS off-chip signal driver with 2.5-3x smaller di/dt noise than the conventional design without incurring additional signal delay is described. It minimizes L di/dt effects by reducing the output signal swing by about a factor of 2 and by providing a controlled ramp rate for the output current. The circuit has a nearly-constant output resistance for source termination of transmission lines. A receiver designed for the smaller signal swing is also described. Simulations show a driver-receiver delay of 3 ns for a 7.5 cm line on a multichip package with a peak di/dt of only 12 mA/ns. Driver-receiver delay and noise measurements are also presented.