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US 8,941,439 B2Granted
Differential charge reduction
AssigneeAnalog Devices, Inc.
InventorsScott G. Bardsley, Peter Derounian, Franklin M. Murden
Life of this patent
Estimating the term…
Abstract
One embodiment relates to an apparatus configured to cancel charge injected on a node of a differential pair of nodes. A dummy circuit element can inject charge on an inverted node to cancel charge injected on a non-inverted node by a switch when the switch is switched off. In addition, another dummy circuit element can inject charge on the non-inverted node to cancel charge injected on the inverted node by another switch when the other switch is switched off. These dummy circuits elements can be cross-coupled.
Claims24
An apparatus comprising:
- a first switch configured to receive a first differential input and to provide the first differential input to a first node when switched on;
- a second switch configured to receive a second differential input and to provide the second differential input to a second node when switched on, wherein the first node and the second node are a differential pair of nodes;
- a first dummy circuit element configured to inject charge on the second node to cancel charge injected on the first node by the first switch when the first switch is switched off;
- and
- a second dummy circuit element configured to inject charge on the first node to cancel charge injected on the second node by the second switch when the second switch is switched off;
- wherein the first switch comprises a first field effect transistor, wherein the second switch comprises a second field effect transistor, wherein the first dummy circuit element comprises a first dummy field effect transistor, wherein the second dummy circuit element comprises a second dummy field effect transistor, and wherein the first dummy field effect transistor and the second dummy field transistor each have a gate biased to a power rail voltage.
3 more elements
An apparatus comprising an interleaved analog-to-digital converter stage, the interleaved analog-to-digital converter stage comprising:
- an amplifier comprising a non-inverted input and an inverted input;
- and
- a plurality of channels, each of the plurality of channels comprising:
- a pair of amplifier input switches comprising:
- a first switch configured to receive a first switch input, provide the first switch input to the non-inverted input of the amplifier when switched on, and to electrically isolate the non-inverted input of the amplifier from the first switch input when switched off;
- and
- a second switch configured to receive a second switch input, provide the second switch input to the inverted input of the amplifier when switched on, and to electrically isolate the inverted input of the amplifier from the second switch input when switched off;
- and
- a pair of dummy circuit elements cross coupled between the inputs of the pair of amplifier input switches and the inputs of the amplifier, each dummy circuit element of the pair of dummy circuit elements having substantially the same capacitance as the first switch when the first switch is switched off;
- wherein the pair of amplifier input switches of one of the plurality of channels is configured to provide charge to the non-inverted and the inverted inputs of the amplifier, when the pair of amplifier input switches of the other of the plurality of channels are switched off.
7 more elements
An apparatus comprising:
- an amplifier comprising a non-inverted input and an inverted input;
- and
- a plurality of channels, each of the plurality of channels comprising:
- a pair of amplifier input switches comprising:
- a first switch configured to receive a first switch input, provide the first switch input to the non-inverted input of the amplifier when switched on, and to electrically isolate the non-inverted input of the amplifier from the first switch input when switched off;
- and
- a second switch configured to receive a second switch input, provide the second switch input to the inverted input of the amplifier when switched on, and to electrically isolate the inverted input of the amplifier from the second switch input when switched off;
- and
- a pair of dummy circuit elements cross coupled between the inputs of the pair of amplifier input switches and the inputs of the amplifier, each dummy circuit element of the pair of dummy circuit elements having substantially the same capacitance as the first switch when the first switch is switched off;
- wherein the pair of amplifier input switches of one of the plurality of channels is configured to provide charge to the non-inverted and the inverted inputs of the amplifier, when the pair of amplifier input switches of the other of the plurality of channels are switched off,
- wherein a first dummy circuit element of the pair of dummy circuit elements of a selected channel of the plurality of channels is configured to inject charge on the inverted amplifier input to compensate for a voltage glitch on the first switch input when the selected channel is in a mode other than gain mode and a different channel of the plurality of channels is in a gain mode.
8 more elements
An electronically-implemented method of reducing differential change, the method comprising:
- biasing a first switch to electrically isolate a non-inverting node from an input of the first switch;
- and
- while the first switch is biased to electrically isolate the non-inverting node from the input of the first switch, coupling charge on an inverting node to at least partially cancel charge injected on the non-inverting node by the first switch, wherein said coupling is performed by a dummy switch having a gate biased to a power rail voltage;
- wherein the non-inverting node and the inverting node comprise nodes of a differential pair.
1 more element
An electronically-implemented method of reducing differential change, the method comprising:
- biasing a first switch to electrically isolate a non-inverting node from an input of the first switch;
- and
- while the first switch is biased to electrically isolate the non-inverting node from the input of the first switch, coupling charge on an inverting node to at least partially cancel charge injected on the non-inverting node by the first switch;
- wherein the non-inverting node and the inverting node comprise nodes of a differential pair,
- wherein the method is performed for sampling in an analog-to-digital converter having a plurality of interleaved channels, and wherein the method further comprises:
- turning on amplifier input switches including the first switch of a first channel of a plurality of interleaved channels to provide a sample to the non-inverting node;
- and
- while the amplifier input switches of the first channel are turned on,
- biasing amplifier input switches of the others of the plurality of interleaved channels to be switched off, the others of the plurality of interleaved channels comprising at least a second channel;
- and
- activating switches of the second channel to charge capacitors of the second channel with inputs to the second channel.
8 more elements
Dependencies are inferred from the claim text.