Differential opto isolator
AssigneeAnalog Devices, Inc.
InventorsCheck F. Lee, Baoxing Chen
Life of this patent
Estimating the term…
Abstract
Isolators and methods for operating the same are described for opto-isolators with improved common mode transient immunity (CMTI). In some embodiments, a pair of photodetectors are provided in the opto-isolator and configured to generate photocurrents of opposite signs or directions in response to a light signal. Photocurrents from the pair of photodetectors are combined in a differential manner to represent data transmitted in a light signal, while common mode transient noise at the two photodetectors is attenuated or eliminated.
Claims20
An isolator, comprising:
- an input terminal and an output terminal electrically isolated from the input terminal;
- a light source coupled to the input terminal and configured to transmit a light signal representing an input electric signal at the input terminal;
- a first photodetector coupled between a first node and a second node, the first photodetector configured to receive the light signal and generate a first photocurrent from the first node toward the second node in response to the light signal;
- a second photodetector coupled between a third node and a fourth node, the second photodetector configured to receive the light signal and generate a second photocurrent from the third node toward the fourth node in response to the light signal;
- and
- differential amplifier circuitry coupled to the second node, the third node and the output terminal, wherein the differential amplifier circuitry is configured to generate an output electric signal at the output terminal based on a difference between the first photocurrent and the second photocurrent.
A semiconductor package, comprising:
- a semiconductor substrate comprising a first photodetector and a second photodetector disposed on a first surface of the semiconductor substrate;
- an input terminal and an output terminal electrically isolated from the input terminal;
- a light source coupled to the input terminal and configured to transmit a light signal representing an input electric signal at the input terminal, wherein the first photodetector is coupled between a first node and a second node, and is configured to receive the light signal and generate a first photocurrent from the first node toward the second node in response to the light signal, and
- wherein the second photodetector is coupled between a third node and a fourth node, and configured to receive the light signal and generate a second photocurrent from the third node toward the fourth node in response to the light signal;
- and
- differential amplifier circuitry coupled to the second node, the third node and the output terminal, wherein the differential amplifier circuitry is configured to generate an output electric signal at the output terminal based on a difference between the first photocurrent and the second photocurrent.
A method for operating an isolator having an input terminal and an output terminal electrically isolated from the input terminal, the method comprising:
- providing an input electric signal at the input terminal;
- transmitting, by a light source coupled to the input terminal, a light signal representing the input electric signal;
- receiving the light signal at a first photodetector coupled between a first node and a second node;
- generating, by the first photodetector, a first photocurrent from the first node toward the second node in response to the received light signal;
- receiving the light signal at a second photodetector coupled between a third node and a fourth node;
- generating, by the second photodetector, a second photocurrent from the third node toward the fourth node in response to the received light signal;
- generating, by differential amplifier circuitry coupled to the second node, the third node and the output terminal, an output electric signal at the output terminal based on a difference between the first photocurrent and the second photocurrent.
Dependencies are inferred from the claim text.