Analog Devices,inc.

William G J Schofield

Douglas A Mercer

A 2&#x2212;1 shuffling network includes a shuffle exchange network for receiving 2&#x2212;1 data inputs and a dummy input and providing 2outputs; a replacement set of 2&#x2212;1 data switches for receiving 2&#x2212;1 outputs from the shuffle exchange network; and a selection circuit for actuating selective ones of the 2&#x2212;1 data switches in the replacement set to replace one of the 2&#x2212;1 outputs of the shuffle exchange network with a 2output of the shuffle exchange network.

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Methods and devices for code independent switching in a digital-to-analog converter (DAC) are described. A synchronous digital circuit is triggered by a clocking signal and develops a digital data signal. A current steering circuit has a common source node for supplying current, and develops an analog output signal representative of the digital data signal. Any switching disturbances at the common source node are substantially data independent.

Current DAC code independent switching

A digital to analog converter circuit is segmented into a main digital to analog converting unit including a plurality of current sources and a plurality of cascode units, each current source being connected to a cascode unit and a sub-digital to analog converting unit including a current source connected to a plurality of cascode units. A cascode bias unit is operatively connected to each cascode unit of the main digital to analog converting unit so as to bias each current source of the main digital to analog converting unit to operate at a same drain voltage. A second cascode bias unit is operatively connected to each cascode unit of the sub-digital to analog converting unit so as to bias the current source of the sub-digital to analog converting unit to operate at a same drain voltage. A reference voltage source is operatively connected to an input of the first cascode bias unit and connected to an input of the second cascode bias unit. The tying of the reference voltage source to both cascode bias circuits causes the operating emitter/source to collector/drain voltage of each current source transistor of the main digital to analog converting unit to be equal to the operating emitter/source to collector/drain voltage of the current source transistor of the sub-digital to analog converting unit.

Digital/analog converter including gain control for a sub-digital/analog converter

A calibrated current source includes current source having an output node; a calibration circuit; a load circuit; a cascode switching circuit including a pair of cascode switches, one connected between the local circuit and output node, the other connected between the calibration circuit and the output node; and a bias circuit selectively applying a bias voltage to the cascode switches to selectively connect the load circuit and the calibration circuit to the output node while maintaining a constant voltage at the output node and across the current source to provide a consistent current to the load and calibration circuits.

Calibrated current source

A multistage scrambler for a digital to analog converter having a non-ideal transfer function resulting from an error function which causes harmonic distortion includes a first shuffling network having a first input for receiving digital data and a first output, the first shuffling network including a first set of data switches; a first sequence generator for selectively interconnecting the first set of data switches to reorder at the first output the digital data received at the first input to reduce the harmonic distortion to lower magnitude colored noise; a second shuffling network having a second input for receiving the reordered digital data from the first output and a second output, the second shuffling network including a second set of data switches; and a second sequence generator for selectively interconnecting the second set of data switches to reorder at the second output the digital data received at the second input to transform the colored noise toward lower power white noise.

Multistage scrambler for a digital to analog converter

A non-linear bulk capacitance bootstrapped current switch includes a current switch circuit including a source node and a first bulk connection having a first bulk capacitance associated with it; a current defining circuit connected to the source node and having a second bulk connection having a second bulk capacitance associated with it; and a tracking circuit for driving the voltage on at least one of the first and second bulk connections in response to the voltage on the source node to reduce the associated non-linear bulk capacitance.

Non-linear bulk capacitance bootstrapped current switch

A current switching cell for a multi-cell DAC, each cell having a data input and an analog output and including a current switching circuit having a current node; a current definition circuit for providing current to the current switching circuit at the current node; the current definition circuit having a parasitic coupling between the input and the current node; a driver circuit responsive to a data input for actuating the current switching circuit to provide an analog output from the current from the current definition circuit; and a control circuit responsive to at least one common control signal for controlling the current definition circuit and isolating the parasitic coupling between the current node and the common control signal; the driver circuit may also have a parasitic coupling between its driver input and the current node and the control circuit may isolate the parasitic coupling between the current node and the driver input.

Current switching cell for digital to analog converter

A method of equalizing total signal delay across a digital to analog interface includes constructing a plurality of unit digital to analog converter cells each having a clock input and a data input and an analog output; constructing an analog output network for summing the analog outputs for delivery to a termination which in combination with the analog output network defines a first predetermined time delay between the unit cells; constructing a clock input distribution network for propagating a clock input to each of the unit cells tapped along the clock input distribution network; and connecting a second termination to the clock input distribution network for establishing the clock input distribution network as a transmission line and defining in combination with the clock input distribution network a second predetermined time interval delay between the clock input to the unit cells equal to the first predetermined in the interval delay for synchronizing the propagation of the clock inputs propagating along the clock input distribution network with the analog outputs propagating along the analog output network.

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North Andover, MA, United States of America

William G J Schofield