Analog Devices,inc.

Michael Christian Wohnsen Coln

Gary Carreau

Michael Mueck

John Jude O'Donnell

Bruce E Amazeen

Maria Del Mar Chamarro Marti

A Successive Approximation Routine converter is provided in which a comparator is responsive to an output of a first Digital to Analog Converter, and an output of a second Digital to Analog Converter and to a DAC common mode output reference voltage, and wherein the comparator provides data to a SAR controller indicating which one of the DAC outputs is greater than the other, and how a common mode voltage on the DAC outputs compares to the reference voltage. On this basis the SAR controller can add or subtract a common mode offset to the trial words being presented at a given bit trial such that both differential and common mode convergence is achieved.

Differential input successive approximation analog to digital converter with common mode rejection

An open drain driver () selectively switches a MOSFET switch (MN) which is passively held in the conducting state into the non-conducting state. The MOSFET switch (MN) switches an AC analogue input signal on a main input terminal () to a main output terminal () and the gate of the MOSFET switch (MN) is AC coupled by a capacitor (C) to the drain thereof. The open drain driver () comprises a first MOSFET (MN) and a second MOSFET (MN) through which the gate of the MOSFET switch (MN) is pulled to ground (V). The gate of the first MOSFET (MN) is coupled to the supply voltage (V) for maintaining the first MOSFET (MN) in the open state. A control signal is applied to the gate of the second MOSFET (MN) for selectively operating the open drain driver () in the conducting state for operating the MOSFET switch (MN) in the non-conducting state. When the second MOSFET (MN) is in the non-conducting state, the first MOSFET (MN) remains in the conducting state until the voltage on a coupling node () between the first and second MOSFETs (MN,MN) equals the difference between its gate voltage and its threshold voltage, at which stage, any over-voltages applied to the gate of the MOSFET switch (MN) are divided between the first and second MOSFETs (MN,MN). A coupling diode (D) coupling the coupling node () to the supply voltage (V) clamps the voltage on the coupling node () at the supply voltage (V) plus the conducting voltage of the diode (D), in the event of the voltage on the coupling node () rising after the first MOSFET (MN) has gone into the non-conducting state. The coupling node () may be capacitively coupled to the supply voltage (V) by a coupling capacitor instead of or as well as the diode (D) for limiting the voltage on the coupling node ().

Open drain driver, and a switch comprising the open drain driver

Quasi-differential successive-approximation methods and structures are provided for converting analog signals into corresponding digital signals. These methods and structures realize the signal-to-noise improvements of fully-differential SAR ADCs and the calibration accuracy improvements of pseudo-differential SAR ADCs. Structures of the invention operate in a fully-differential mode to establish more-significant bits of the corresponding digital signals and in a pseudo-differential mode to establish the less-significant bits.

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Lexington, MA, United States of America

Michael Christian Wohnsen Coln