APPLICATIONS
Overview A primary problem for the Firewire IEEE1394 and USB2.0 as with the USB1.1 port designer is common mode noise conducted through the power and signal lines from various sources. EMI susceptibility on data/power lines is also a major concern. Steward’s CM2722 (for single and dual ports), CM3822 (for tri ports), and CM5022 (for quad ports) series of components have the lowest normal mode impedance in the industry and suppress a wide range of digital common mode noise. Normal mode impedance is net circuit impedance i.e. the impedance seen by the differential signal. Discussion Firewire and USB2.0 is a serial data / power port providing a broad range of data and current loads. The initial USB industry specification called for a serial port which operates in a hybrid full duplex mode and a power port that operates up to 1 amp of current. This design has created several layers of EMI problems that must be corrected. Also, USB component performance requirements have been stretched beyond initial specifications which has caused field failures of 1 amp and even 3 amp rated ferrite chip beads.
