Differential communication circuit

Patent metadata

Field	Value
Publication number	US-11831471-B2
Application number	US-202217841030-A
Country	US
Kind code	B2
Filing date	Jun 15, 2022
Priority date	Jun 17, 2021
Publication date	Nov 28, 2023
Grant date	Nov 28, 2023

Abstract

A differential communication circuit is connected to a communication line formed of a positive communication line and a negative communication line for differential communication. The differential communication circuit includes: a series circuit that includes a resistor element and a connection switch. The resistor element is connected between the positive and negative communication lines when the connection switch is turned on. The circuit also includes a transmission unit that is configured to output a differential signal to the communication line and a controller that is configured to change impedance of the communication line by turning on the connection switch in a period during which the transmission unit does not output the differential signal.

First claim

The invention claimed is:

1. A differential communication circuit connected to a communication line formed of a positive communication line and a negative communication line for differential communication, the differential communication circuit comprising:
a series circuit that includes a resistor element and a connection switch, the resistor element being connected between the positive and negative communication lines when the connection switch is turned on;
a transmission unit that is configured to output a differential signal to the communication line; and
a controller that is configured to change impedance of the communication line by turning on the connection switch in a period during which the transmission unit does not output the differential signal.

2. The differential communication circuit according to claim 1 , wherein
the communication line has a terminating resistor that has a resistance value larger than characteristic impedance of the communication line, and
the resistor element is configured to have a resistance value such that a combined resistance value of the resistor element and the terminating resistor upon turning on the connection switch is equal to the characteristic impedance of the communication line.

3. The differential communication circuit according to claim 1 , further comprising:
a receiving unit that is configured to receive the differential signal output to the communication line, wherein
the controller is configured to turn off the connection switch for a period during which the receiving unit receives the differential signal, and
the controller is configured to turn on the connection switch when the transmission unit does not output the differential signal in a signal transmission period so that a multi-valued differential signal is transmitted.

4. The differential communication circuit according to claim 1 , further comprising:
a common voltage circuit that is configured to apply a common voltage to each of the positive and negative communication lines, wherein
the series circuit is formed by connecting, in series, a positive resistor element and a positive connection switch to a negative resistor element and a negative connection switch, and
a common connection point between the positive connection switch and the negative connection switch is connected to a feed point of the common voltage circuit.

5. The differential communication circuit according to claim 1 , further comprising:
an amplitude correcting unit that is configured to more increase an amplitude of the differential signal in a signal rise time generated when the transmission unit starts outputting the differential signal than during other periods.

6. The differential communication circuit according to claim 5 , wherein
the amplitude correcting unit is configured to temporarily increase a value of current supplied by the transmission unit to the communication line.

7. The differential communication circuit according to claim 6 , wherein
the transmission unit includes:
a power supply side switch and a ground side switch that are connected to each other in series and have a common connection point connected to the positive communication line;
a power supply side switch and a ground side switch that are connected to each other in series and have a common connection point connected to the negative communication line;
a power supply side resistor element that is connected between a power supply and the power supply side switch; and
a current mirror circuit that is connected between the ground side switch and a ground, and

the amplitude correcting unit is a capacitor that is connected between a mirror pair constituting the current mirror circuit and a common connection point of the power supply side resistor element and the power supply side switch.

Assignees

• Denso Corp
• Toyota Motor Co Ltd
• MIRISE Technologies Corporation

Inventors

• Otsuka Shigeki
• Na Hyoungjun
• Ito Takasuke
• Furuta Yoshikazu
• Nezuka Tomohiro

Classifications

• H04L25/0272 Primary

  Arrangements for coupling to multiple lines, e.g. for differential transmission · CPC title

• H04B3/56 Primary

  Circuits for coupling, blocking, or by-passing of signals · CPC title

• H04L25/0278

  Arrangements for impedance matching · CPC title

• H04L12/10 Primary

  Current supply arrangements · CPC title

• H04L25/026

  Arrangements for coupling transmitters, receivers or transceivers to transmission lines; Line drivers (duplexing arrangements H04L5/14) · CPC title