Abstract: A USB interface having improved EMC immunity where the D+, D?, and USB ground lines each pass through a common mode choke. The USB 5V line is AC coupled to the USB ground line outside the choke and routed through a high impedance into the circuit while maintaining the integrity of the signal. In addition, bypass capacitors, such as Tantalum bypass capacitors, and a 5.6V Transorb device are added to the 5V power supply of the controller, and all unused pins are terminated to reduce unwanted ringing transients in the controller leadframe. In addition, small capacitors within the capacitive loading specification allowed by the USB-IF are positioned next to the controller on each data line.

Abstract: An inrush circuit for electronic devices is particularly useful for point-of-sale printers. The circuit applies an active feedback-controlled voltage ramp to a bulk capacitor by means of a P-channel field effect transistor that is operated linearly after a controlled delay for contact bounce.

Abstract: A USB interface having improved EMC immunity where the D+, D?, and USB ground lines each pass through a common mode choke. The USB 5V line is AC coupled to the USB ground line outside the choke and routed through a high impedance into the circuit while maintaining the integrity of the signal. In addition, bypass capacitors, such as Tantalum bypass capacitors, and a 5.6V Transorb device are added to the 5V power supply of the controller, and all unused pins are terminated to reduce unwanted ringing transients in the controller leadframe. In addition, small capacitors within the capacitive loading specification allowed by the USB-IF are positioned next to the controller on each data line.

Abstract: An inrush circuit for electronic devices is particularly useful for point-of-sale printers. The circuit applies an active feedback-controlled voltage ramp to a bulk capacitor by means of a P-channel field effect transistor that is operated linearly after a controlled delay for contact bounce.

Abstract: A circuit is provided for regulating the application of power to a load which is relatively insensitive to rapid power fluctuation of the type exemplified by typical AC line sources. In one embodiment, an AC line source is applied at a controlled rate to a tungsten lamp whose operation is controlled by a transistor switching network. The transistor operation, in turn, is controlled by comparing a portion of the rectified signal with a signal proportional to the light output of the lamp.