Texas Instruments Corporation

William A Severin

James Robert Hochschild

Henry T Yung

Sabrina D Phillips

Edward R Klinkovsky

A multi-mode analog to digital converter is described for converting an analog input into a digital value according to a linear or a companding transfer function. The converter comprises a comparator, a successive approximation register and a charge redistribution device. The comparator compares the input voltage and a generated voltage. The successive approximation register generates a provisional binary word responsive to the output of the comparator. The charge redistribution device generates the generated voltage according to the provisional binary word and to a selected transfer function. The transfer function may be selected from the group consisting of linear and companding.

Linear/companding A/D converter

A multi-mode digital to analog converter for converting a digital input into an analog voltage according to a linear or a companding transfer function. The converter comprises a charge redistribution device for creating an analog voltage at a node and switching circuitry for controlling the charge redistribution device. The switching circuitry is operable to effect either transfer function responsive to its inputs.

Multi-mode digital to analog converter and method

A biquadrature switched capacitor filter having differential input/output integrator amplifiers (12,34) and switched capacitor networks (16,28,36,40). The differential outputs of one amplifier (12) are crossed and connected to the switched capacitor networks (36,40) of the other amplifier (34) to provide a negative capacitance effect. Feedforward capacitors (70,72) are switched to prevent the stage input signals (IN+, IN-) from being coupled during certain phases of a biphase nonoverlapping clock. In high-pass applications, a feedback capacitor (134, 136) makes positioning of pole and zero responses easy. Amplifier bandwidth is controlled by switched capacitors (148, 152) connected to the amplifiers during certain clock phases.

Switched capacitor filter

A PSK integrated circuit modem employs multi-mode filters in its switched capacitor circuitry for providing a plurality of filter response to accomodate a plurality of modem protocols. Each capacitor is selectively connected or disconnected from the circuit by a transistor switch, and selectively connected and disconnected from the circuit voltage reference by a transistor switch. The switches operate out of phase with each other so that when any capacitor is connected in the circuit, it is disconnected from the reference voltage and when any capacitor is disconnected from the circuit, it is connected to the reference voltage. The modem switch minimizes the effect of stray capacitance from the unselected capacitors and their associated transistor switches that have been turned off.

PSK modem filter switch

An integrated circuit demodulator receives an alternating signal at a first frequency and an alternating signal at a second frequency and provides a binary output corresponding to the first and second frequencies. An input signal is received by a first and a second frequency filter. If the input signal is the first frequency, then it is attenuated in the second frequency filter and vice versa. A positive full wave rectifier receives the first frequency signal and provides a positive full wave rectification thereof. A negative full wave rectifier receives the second frequency signal and provides a negative full wave rectification thereof. The rectifications are summed in an operational amplifier, thereby providing a difference so that the positive rectification is reduced by the attenuated negative rectification and the negative rectification is reduced by the attenuated positive rectification. A binary output is thereby provided.

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Allen, TX, United States of America

William A Severin