LOW L di/dt NOISE OFF-CHIP DRIVER
Original Publication Date: 1988-Feb-01
Included in the Prior Art Database: 2005-Feb-14
An OCD (Off-Chip Driver) transistor in MOS (Metal-Oxide Semiconductor) chips must have a large W/L ratio to drive a large capacitive load at a minimum delay. The large transistor, however, causes L di/dt noise because of its sharp switching characteristic. The voltage spike on the ground line and/or power supply line appears at an early stage of the switching process. The present circuits alleviate the L di/dt noise by controlling the initial switching characteristic. Fig. 1 shows an OCD circuit implemented by NMOS FETs (N-Channel MOS Field-Effect Transistors). This circuit is intended to alleviate the L di/dt undershoot noise induced in the ground line by the sharp turn-on switching of a large OCD transistor T5. It is now assumed that capacitive load CL has been charged by input signal IN being high and thus node N2 is high.