Transmitter circuit, receiver circuit, interface circuit, and electronic instrument

• US 20060097753A1
• Filed: 09/07/2004
• Published: 05/11/2006
• Est. Priority Date: 09/05/2003
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Saito, Nobuyuki, Shibata, Yukinari, Hasegawa, Tomonaga, Ishida, Takuya
• Granted Patent: US 7,218,146 B2
• Time in Patent Office: Days
• US Class Current: 326/83
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: H04L 25/0276 Arrangements for coupling common mode signals
• CPC Class Codes: H04L 25/0282 Provision for current-mode coupling
• CPC Class Codes: H04L 25/0294 Provision for current-mode coupling
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A transmitter circuit including: a current driver which current-drives differential signal lines; and a voltage driver which is electrically disconnected from at least one of the differential signal lines in a normal transfer mode, and is electrically connected to the at least one of the differential signal lines and voltage-drives the at least one of the differential signal lines in a power-down mode. The voltage driver outputs a power-down voltage for setting a receiver circuit to the power-down mode or a wakeup voltage for canceling the power-down mode of the receiver circuit, to the at least one of the differential signal lines. The current driver transmits a power-down command to the receiver circuit by current-driving the differential signal lines in the normal transfer mode.

Claims

1. A transmitter circuit connected to a receiver circuit with differential signal lines interposed, the transmitter circuit comprising:

a current driver which current-drives the differential signal lines; and

a voltage driver which is electrically disconnected from at least one of the differential signal lines in a normal transfer mode, and is electrically connected to the at least one of the differential signal lines and voltage-drives the at least one of the differential signal lines in a power-down mode,

wherein the voltage driver outputs a power-down voltage for setting the receiver circuit to the power-down mode or a wakeup voltage for canceling the power-down mode of the receiver circuit, to the at least one of the differential signal lines.

2. The transmitter circuit as defined in claim 1,

wherein the current driver transmits a power-down command to the receiver circuit by current-driving the differential signal lines in the normal transfer mode.

3. The transmitter circuit as defined in claim 1,

wherein the current driver includes:

a first current source provided between a first output node for a first signal line of the differential signal lines and a first power supply; and

a second current source provided between a second output node for a second signal line of the differential signal lines and the first power supply, and

wherein the voltage driver includes;

a voltage output circuit which outputs the power-down voltage or the wakeup voltage; and

a switching element which is disposed between an output of the voltage output circuit and at least one of the first and second output nodes, turned OFF in the normal transfer mode and turned ON in the power-down mode.

4. An interface circuit having differential signal lines, the interface circuit comprising:

the transmitter circuit as defined in claim 1 connected to a receiver circuit of a partner device with first differential signal lines interposed to current-drive the first differential signal lines; and

another receiver circuit connected to another transmitter circuit of the partner device with second differential signal lines interposed, the transmitter circuit of the partner device current-driving the second differential signal lines,

wherein the receiver circuit of the interface circuit connected to the second differential signal lines includes a wakeup detection circuit, the wakeup detection circuit being set to a disabled state in the normal transfer mode, being set to an enabled state in the power-down mode, and detecting the wakeup voltage to output a signal used to cancel the power-down mode when the transmitter circuit of the partner device has outputted the wakeup voltage to at least one of the second differential signal lines by voltage drive.

5. An interface circuit having differential signal lines, the interface circuit comprising:

the transmitter circuit as defined in claim 1 connected to a receiver circuit of a partner device with first differential signal lines interposed to current-drive the first differential signal lines; and

another receiver circuit connected to another transmitter circuit of the partner device with second differential signal lines interposed, the transmitter circuit of the partner device current-driving the second differential signal lines,

wherein the receiver circuit of the interface circuit connected to the second differential signal lines includes a wakeup detection circuit, the wakeup detection circuit outputting a wakeup signal when cancellation of the power-down mode is detected after the receiver circuit of the interface circuit has been set to the power-down mode by output of the power-down voltage to the at least one of the second differential signal lines from the transmitter circuit of the partner device.

19. An electronic instrument comprising:

the interface circuit as defined in claim 4;

and

at least one of a communication device, a processor, an imaging device, and a display device.

20. An electronic instrument comprising:

the interface circuit as defined in claim 5;

and

at least one of a communication device, a processor, an imaging device, and a display device.

6. A receiver circuit connected to a transmitter circuit which current-drives differential signal lines with the differential signal lines interposed, the receiver circuit comprising:

a current/voltage conversion circuit which performs a current/voltage conversion based on a current flowing through the differential signal lines, and outputs first and second voltage signals which form differential voltage signals;

a comparator which compares the first and second voltage signals and outputs an output signal; and

a wakeup detection circuit which is set to a disabled state in a normal transfer mode and to an enabled state in a power-down mode, detects a wakeup voltage and outputs a signal which is used to cancel the power-down mode when the transmitter circuit has outputted the wakeup voltage to at least one of the differential signal lines by voltage drive.

7. The receiver circuit as defined in claim 6, further comprising:

a power-down detection circuit which detects a power-down command based on a comparison result from the comparator when the transmitter circuit has transmitted the power-down command by current-driving the differential signal lines in the normal transfer mode; and

a power-down setting circuit which sets at least one of the current/voltage conversion circuit and the comparator to the power-down mode and sets the wakeup detection circuit to an enabled state, when the power-down detection circuit has detected the power-down command.

8. The receiver circuit as defined in claim 7,

wherein the power-down setting circuit includes a holding circuit which holds power-down setting information when the power-down command is detected, until the power-down mode is canceled;

and

wherein the power-down setting circuit sets at least one of the current/voltage conversion circuit and the comparator to the power-down mode and sets the wakeup detection circuit to the enabled state when the power-down setting information is held by the holding circuit.

9. The receiver circuit as defined in claim 7,

wherein the power-down setting circuit cancels the power-down mode, sets at least one of the current/voltage conversion circuit and the comparator to the normal transfer mode, and sets the wakeup detection circuit to a disabled state when the wakeup voltage is detected.

10. The receiver circuit as defined in claim 7,

wherein the transmitter circuit connected to the receiver circuit with the differential signal lines interposed transmits a plurality of power-down commands by current-driving the differential signal lines;

and

wherein the power-down setting circuit sets at least one of the current/voltage conversion circuit and the comparator to the power-down mode when the power-down detection circuit detects the plurality of power-down commands.

11. The receiver circuit as defined in claim 7,

wherein the transmitter circuit transfers a special code obtained by using an encoding method which expands a bit width, as the power-down command;

and

wherein the power-down detection circuit detects the power-down command by detecting the special code.

15. An interface circuit having a differential signal interface, the interface circuit comprising:

the receiver circuit as defined in claim 6 connected to a transmitter circuit of a partner device with first differential signal lines interposed, the transmitter circuit of the partner device current-driving the first differential signal lines; and

another transmitter circuit connected to another receiver circuit of the partner device with second differential signal lines interposed to current-drive the second differential signal lines,

wherein the transmitter circuit of the interface circuit connected to the second differential signal lines includes;

a current driver which current-drives the second differential signal lines; and

a voltage driver which is electrically disconnected from the at least one of the second differential signal lines in a normal transfer mode, and is electrically connected to the at least one of the second differential signal lines and voltage-drives the at least one of the second differential signal lines in a power-down mode; and

wherein the voltage driver outputs a power-down voltage for setting the receiver circuit of the partner device to the power-down mode or a wakeup voltage for canceling the power-down mode of the receiver circuit of the partner device, to the at least one of the second differential signal lines.

17. An interface circuit having a differential signal interface, the interface circuit comprising:

the receiver circuit as defined in claim 6 which is used for data transfer and is connected to a data transfer transmitter circuit with data transfer differential signal lines interposed, the data transfer transmitter circuit current-driving the data transfer differential signal lines; and

a clock transfer receiver circuit connected to a clock transfer transmitter circuit with clock transfer differential signal lines interposed, the clock transfer transmitter circuit current-driving the clock transfer differential signal lines,

wherein the data transfer receiver circuit outputs a signal for canceling a power-down mode of the clock transfer receiver circuit when the power-down mode of the data transfer receiver circuit is canceled.

21. An electronic instrument comprising:

the interface circuit as defined in claim 15;

and

at least one of a communication device, a processor, an imaging device, and a display device.

23. An electronic instrument comprising:

the interface circuit as defined in claim 17;

and

at least one of a communication device, a processor, an imaging device, and a display device.

12. A receiver circuit connected to a transmitter circuit which current-drives differential signal lines with the differential signal lines interposed, the receiver circuit comprising:

a current/voltage conversion circuit which performs a current/voltage conversion based on a current which flows through the differential signal lines, and outputs first and second voltage signals which form differential voltage signals;

a comparator which compares the first and second voltage signals and outputs an output signal; and

a wakeup detection circuit which outputs a wakeup signal when cancellation of a power-down mode is detected after setting of the receiver circuit to a power-down mode by outputting a power-down voltage to at least one of the differential signal lines from the transmitter circuit.

13. The receiver circuit as defined in claim 12, further comprising:

a power-down detection circuit which detects a power-down command based on a comparison result from the comparator when the transmitter circuit has transmitted the power-down command by current-driving the differential signal lines in a normal transfer mode; and

a power-down setting circuit which sets at least one of the current/voltage conversion circuit and the comparator to the power-down mode when the power-down detection circuit has detected the power-down command and the transmitter circuit has output the power-down voltage to the at least one of the differential signal lines.

14. The receiver circuit as defined in claim 13,

wherein the wakeup detection circuit makes the wakeup signal active when a voltage level of the at least one of the differential signal lines changes from a power-down voltage level to another voltage level after the power-down command has been detected and an output signal of the power-down detection circuit has been made active.

16. An interface circuit having a differential signal interface, the interface circuit comprising:

the receiver circuit as defined in claim 12 connected to a transmitter circuit of a partner device with first differential signal lines interposed, the transmitter circuit of the partner device current-driving the first differential signal lines; and

another transmitter circuit connected to another receiver circuit of the partner device with second differential signal lines interposed to current-drive the second differential signal lines,

wherein the transmitter circuit of the interface circuit connected to the second differential signal lines includes;

a current driver which current-drives the second differential signal lines; and

a voltage driver which is electrically disconnected from the at least one of the second differential signal lines in a normal transfer mode, and is electrically connected to the at least one of the second differential signal lines and voltage-drives the at least one of the second differential signal lines in a power-down mode; and

wherein the voltage driver outputs a power-down voltage for setting the receiver circuit of the partner device to the power-down mode or a wakeup voltage for canceling the power-down mode of the receiver circuit of the partner device, to the at least one of the second differential signal lines.

18. An interface circuit having a differential signal interface, the interface circuit comprising:

the receiver circuit as defined in claim 12 which is used for data transfer and is connected to a data transfer transmitter circuit with data transfer differential signal lines interposed, the data transfer transmitter circuit current-driving the data transfer differential signal lines; and

a clock transfer receiver circuit connected to a clock transfer transmitter circuit with clock transfer differential signal lines interposed, the clock transfer transmitter circuit current-driving the clock transfer differential signal lines,

wherein the data transfer receiver circuit outputs a signal for canceling a power-down mode of the clock transfer receiver circuit when the power-down mode of the data transfer receiver circuit is canceled.

22. An electronic instrument comprising:

the interface circuit as defined in claim 16;

and

at least one of a communication device, a processor, an imaging device, and a display device.

24. An electronic instrument comprising:

the interface circuit as defined in claim 18;

and

at least one of a communication device, a processor, an imaging device, and a display device.