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US 5,689,257 AGranted
Skewless differential switch and DAC employing the same
AssigneeAnalog Devices, Inc.
InventorsDouglas A. Mercer, David Reynolds, David H. Robertson, Ernest T. Stroud
Life of this patent
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Abstract
A differential switch accepts a binary control signal and its complement (which may be skewed with respect to the control signal) and latches both signals simultaneously. The latched output signals drive the control terminals of a differential switch pair which connects one of two terminals to a third terminal, depending upon the state of the control terminals. The differential switch may optionally include an inverter which complements the binary control signal, thus eliminating the need for external inversion of the control signal. The switch is particularly applicable for use in a digital to analog converter.
Claims20
A skewless differential switch, comprising:
- a control input for receiving a control signal,
- an inverter that is coupled to said control input to produce a complement of said control signal which is skewed with respect to said control signal,
- an enable input for receiving a clock signal,
- a plurality of storage elements,
- a pair of transfer switches responsive to said clock signal that are connected between said control input and said inverter, respectively, and said storage elements to isolate said control input from said storage elements and, once per clock period, simultaneously transfer the control signal and its complement through the respective switches to the storage elements, said storage elements also connected to store said signals and to provide a pair of de-skewed complementary output signals having the same binary values as the control signal and its complement stored within said storage elements, and
- a differential switch pair having complementary control inputs that are connected to receive said pair of de-skewed complementary output signals from said storage elements so that said differential switch pair is controlled by said control signal without skew.
3 more elements
A digital to analog converter, comprising:
- an analog output section,
- a digital section having a binary output and an enable output connected to provide control over said analog output section,
- said analog output section comprising a differential switch which connects a first or second conducting terminal to a third conducting terminal thereby producing an analog output,
- said differential switch further having a control input connected to said binary output and an enable input connected to said enable output,
- said differential switch further comprising,
- an inverter connected to receive a signal from said control input and to produce a complement of said control signal,
- control and complement inputs for receiving a control signal and a complement of said control signal which may be skewed with respect to said control signal,
- an enable input,
- storage elements,
- switches connected to provide transmission paths under control of said enable input from each of said control and complement inputs to said storage elements, said storage elements also connected to store said signals and to provide de-skewed output signals having the same binary value as the respective signal stored within said storage elements, and
- a differentially connected switches having complementary control inputs, one of said differentially connected switch control inputs being connected to receive said control signal, and the other differentially connected switch control input being connected to receive said complement signal from another of said storage elements.
8 more elements
A differential switch, comprising:
- a control input for receiving a single binary control signal,
- a latch that inverts said control signal thereby introducing a delay between the control signal and its complement and then simultaneously transfers the control signal and its complement through a pair of transfer switches into a plurality of storage elements thereby eliminating the skew between the signals, and
- a pair of differentially connected switches with two control terminals that are connected to the storage elements so that said pair of differentially connected switches are controlled by the single binary control signal without skew.
A digital to analog converter comprising:
- an analog output section,
- a digital section having a binary output and an enable output connected to provide control of said analog output section,
- said analog output section comprising a differential switch which connects a first or second conducting terminal to a third conducting terminal thereby producing an analog output,
- said differential switch further comprising,
- control and complementary inputs for receiving a control signal and its complement,
- a latch having control and complementary inputs which latches said control and complementary signals simultaneously, said latch having two outputs, and
- a pair of differentially connected switches with two control terminals, said switches connecting one of two conducting terminals to a third conducting terminal, depending upon the state of the control terminals said control terminals being connected to said latch outputs.
4 more elements
Dependencies are inferred from the claim text.