Clamp circuit to limit overdrive of off chip driver

摘要

An off-chip driver (OCD) circuit including a clamp circuit to limit overdrive is provided. The circuit comprises an input signal which is inverted to provide an output signal. The driver circuit is comprised of a source-follower transistor to pull-down the output signal. The clamp circuit actively feeds back the source-follower potential to slow down the OCD and minimize ground bounce and noise that causes circuits to fail and signal integrity to be corrupted. The simple drive and clamp circuit is comprised of three transistors, one resistor, and one capacitor. The OCD slew rate is controlled by a current source and provides an output that changes between a positive voltage and ground. The circuit limits dv/dt without using a large resistor as a source follower, hence minimizing the adverse effect on performance.