Vlsi Technology, Inc.

Sung-Hun Oh

D C Sessions

Richard W Ulmer

Elie Georges Khoury

Kenneth M Potts

Richard M Taylor

An improved output driver that minimizes source point reflections when driving a signal on a transmission line by generating a constant source impedance. The improved output driver uses a transistor switching circuit for generating a nearly constant channel impedance when transistor switching circuit is enabled and is not operating in a saturation mode. A switched diode circuit is coupled in parallel to the transistor switching circuit for generating a nearly constant source impedance when a sufficient voltage to bias the switch diode circuit is applied. Control circuitry is coupled to both the transistor switching circuit and to the switched diode circuit for enabling and disabling the transistor switching circuit and the switched diode circuit. By alternatively enabling and disabling the transistor switching circuit and the switched diode circuit the control circuit is able to generate a constant source impedance.

Output driver with constant source impedance

The present invention relates to a process control monitoring system and method. The system and method uses current comparator circuits for monitoring process changes. Process sensitive current sources are compared with weighted reference current sources in a manner that each output of the current comparators demonstrates the inequality of the current sources. By setting the weighted reference current sources properly, the outputs of the current comparators may be used to locate the process corner of the fabricated integrated circuit.

Process control monitoring system and method therefor

A phase-frequency detector for a phase-locked loop (PLL) circuit has symmetrical phase detection characteristics and produces symmetrical activation times on the 'up' and 'down' outputs for connection to a PLL charge pump circuit. The symmetrical characteristics are accomplished by using RS latch circuits at the outputs of the phase-frequency detector to provide the same loads and the same propagation delay for both the 'up' and the 'down' outputs. In addition, cross-wired sequential gates are used for at least some of the gates in the logic gate array of the detector to produce the same propagation delays in the gates.

Symmetrical phase-frequency detector

The present invention relates to a power reduction digital-to-analog (DA) converter current source cell. The power reduction DA converter current source cell is comprised of a DA current source cell for sending a current to a current steering matrix and a switching means coupled to the DA current source cell for dynamically controlling the power dissipation of the DA converter current source cell when the current is not required.

Dynamic power reduction digital-to-analog converter and method therefor

The present invention relates to a system for neutralizing charge injection problems in a switched current system. The system is comprised of a PMOS transistor coupled in parallel with an NMOS switch transistor. If the channel area of the PMOS transistor and the NMOS transistor are equal, then the clock signal to the PMOS transistor must be adjusted to neutralize the negative channel charges of the NMOS transistor. However, if the clock signal to both the PMOS transistor and the NMOS transistor are equal, then the dimension of the PMOS transistor must be smaller than the NMOS transistor in order to neutralize the negative channel charges of the NMOS transistor.

Charge neutralizing system for circuits having charge injection problems

A programmable output pad is disclosed that reduces ground bounce noise and power supply noise under different power supply values and under different load conditions. The programmable output pad comprises a pre-driver, a driver, and a controllable delay. The pre-driver transfers a signal from the input of the output pad to the driver which, in turn, transfers the signal from the pre-driver to an output of the output pad. The controllable delay provides one or more resistors, transistors, transmission gates, or equivalents thereof at the input of the driver which are controlled in order to provide a plurality of different time delays. By selecting these different time delays, the activation of the driver is delayed by different amounts of time. For a given power supply value and load condition, selection of the proper delay effectively reduces both the ground bounce noise on the ground supply of the programmable output pad and the noise on the power supply of the programmable output pad.

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Phoenix, AZ, United States of America

Sung-Hun Oh