US 9,959,536 B1Granted

Current-mode hysteresis comparator

AssigneeSquare, Inc.

InventorsRavi Shivnaraine, Yue Yang, Alain Rousson, Kajornsak Julavittayanukool, Afshin Rezayee

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Abstract

A comparator can incorporate a hysteresis circuit to control when the output of the comparator changes between a high voltage signal and a low voltage signal. The comparator can receive a differential signal and can output either the high voltage signal or the low voltage signal. When the differential input signal is above a first threshold voltage, the output of the comparator can transition to the high voltage signal and when the differential input signal is below a second threshold voltage, the output of the comparator can transition to the low voltage signal. The hysteresis circuit of the comparator is used to adjust the first threshold voltage and the second threshold voltage required to transition the output of the comparator based on the present state of the output signal of the comparator.

Claims28

Dependent claims

A comparator circuit having variable hysteresis, comprising:

a comparator output configured to output a high output voltage or a low output voltage;
a first voltage selection circuit having a first voltage input to receive a first voltage, and configured to selectively provide the high output voltage to the comparator output when the first voltage exceeds a second voltage by more than a first voltage threshold;
a second voltage selection circuit having a second voltage input coupled to receive the second voltage, and configured to selectively provide the low output voltage to the comparator output when the second voltage exceeds the first voltage by more than a second voltage threshold;
a hysteresis current source, wherein a hysteresis current supplied by the hysteresis current source is selectable;
an output feedback circuit coupled to the comparator output and the hysteresis current source, wherein the output feedback circuit is configured to supply the hysteresis current to the first voltage selection circuit when the comparator output is at the low output voltage and to supply the hysteresis current to the second voltage selection circuit when comparator output is at the high output voltage;
a first load resistor coupled to the first voltage selection circuit to conduct the hysteresis current when the hysteresis current is supplied to the first voltage selection circuit, and wherein the first voltage threshold is changed based on the hysteresis current conducted by the first load resistor;
and
a second load resistor coupled to the second voltage selection circuit to conduct the hysteresis current when the hysteresis current is supplied to the second voltage selection circuit, and wherein the second voltage threshold is changed based on the hysteresis current conducted by the second load resistor.

5 more elements

A comparator having hysteresis, comprising:

an input connection;
an output connection;
a first circuit coupled to the input connection to receive an input differential voltage signal from the input connection, the first circuit configured to provide an output differential voltage signal based on the input differential voltage signal, the first circuit comprising a first node coupled to a first resistor and a second node coupled to a second resistor;
a second circuit coupled to the first circuit and the output connection, the second circuit configured to receive the output differential voltage signal from the first circuit, the second circuit configured to provide a logical output signal at the output connection based on the output differential voltage signal, wherein the logical output signal is a first output voltage in response to the output differential voltage signal being a positive voltage and a second output voltage in response to the output differential voltage signal being a negative voltage;
a third circuit coupled to the output connection, the third circuit receiving the logical output signal from the second circuit and providing a hysteresis current to one of the first node or the second node, wherein the third circuit provides the hysteresis current to the first node in response to the logical output signal being the second output voltage and provides the hysteresis current to the second node in response to the logical output signal being the first output voltage, the first resistor configured to provide a first offset voltage in response to conducting the hysteresis current and the second resistor configured to provide a second offset voltage in response to conducting the hysteresis current;
and
wherein the output differential voltage signal transitions from the positive voltage to the negative voltage in response to the input differential voltage signal having a negative value that is less than a negative value of the second offset voltage and the output differential voltage signal transitions from the negative voltage to the positive voltage in response to the input differential voltage signal being greater than the first offset voltage.

4 more elements

A comparator, comprising:

at least one amplifier stage;
at least one filter stage coupled to the at least one amplifier stage;
and
a comparator stage coupled to the at least one filter stage, the comparator stage comprising:
an input connection to receive a differential signal from the at least one filter stage;
an output connection to output a high output voltage or a low output voltage;
a voltage selection circuit having a first voltage input to receive a first voltage from the input connection and a second voltage input to receive a second voltage from the input connection, the voltage selection circuit configured to selectively provide the high output voltage to the output connection when the first voltage exceeds the second voltage by more than a first voltage threshold and to selectively provide the low output voltage to the output connection when the second voltage exceeds the first voltage by more than a second voltage threshold;
a feedback circuit coupled to the output connection and configured to supply a hysteresis current from an adjustable hysteresis current source to a first node of the voltage selection circuit when the output connection is at the low output voltage or to a second node of the voltage selection circuit when the output connection is at the high output voltage;
and
wherein the voltage selection circuit comprises:
a first resistor coupled to the first node, wherein the first resistor is configured to conduct the hysteresis current when the hysteresis current is supplied to the first node, and wherein the first voltage threshold is based on the hysteresis current conducted by the first resistor;
and
a second resistor coupled to the second node, wherein the second resistor is configured to conduct the hysteresis current when the hysteresis current is supplied to the second node, and wherein the second voltage threshold is based on the hysteresis current conducted by the second resistor.

10 more elements

Dependencies are inferred from the claim text.