Transmitter for transmitting a duobinary signal

The present application claims priority under 35 U.S.C. § 119(a) to Korean Patent Application No. 10-2021-0043798, filed on Apr. 5, 2021, which is incorporated herein by reference in its entirety.

1. Technical Field

Various embodiments generally relate to a transmitter for transmitting a duobinary signal.

2. Related Art

FIG. 1 illustrates a circuit diagram of a conventional transmitter 1 .

The conventional transmitter 1 includes a pull-up driving circuit 10 and a pull-down driving circuit 20 .

The pull-up driving circuit 10 is coupled between a first power source VDD and a transmission node Nt, and the pull-down driving circuit 20 is coupled between the transmission node Nt and a second power source GND.

The pull-up driving circuit 10 includes a first PMOS transistor MP 1 and a first pull-up resistor RU 1 that are coupled in series between the first power source VDD and the transmission node Nt.

First data D 1 is input to a gate of the first PMOS transistor MP 1 .

The pull-up driving circuit 10 further includes a second PMOS transistor MP 2 and a second pull-up resistor RU 2 that are coupled in series between the first power source VDD and the transmission node Nt.

Second data D 2 is input to a gate of the second PMOS transistor MP 2 .

The pull-down driving circuit 20 includes a first pull-down resistor RD 1 and a first NMOS transistor MN 1 that are coupled in series between the transmission node Nt and the second power source GND.

The first data D 1 is input to a gate of the first NMOS transistor MN 1 .

The pull-down driving circuit 20 further includes a second pull-down resistor RD 2 and a second NMOS transistor MN 2 that are coupled in series between the transmission node Nt and the second power source GND.

The second data D 2 is input to a gate of the second NMOS transistor MN 2 .

A channel 3 having a shape of a microstrip or the like is positioned between the transmission node Nt and a receiving node Nr.

A receiver 2 includes a termination resistor Rt coupled between the first power source VDD and the receiving node Nr.

In FIG. 1 , a duobinary signal corresponds to level 2 when both the first data D 1 and the second data D 2 are at a low level, the duobinary signal corresponds to level 1 when only one of the first data D 1 and the second data D 2 is at a high level, and the duobinary signal corresponds to level 0 when both the first data D 1 and the second data D 2 are at the high level.

For example, it is assumed that resistance of the termination resistor Rt is 60Ω according to the standard of GDDR (Graphics Double Data Rate), resistance of each of the first and second pull-up resistors RU 1 and RU 2 is 120Ω so that total resistance of the first and second pull-up resistors RU 1 and RU 2 becomes 60Ω, and resistance of each of the first and second pull-down resistors RD 1 and RD 2 is 80Ω so that total resistance of the first and second pull-down resistors RD 1 and RD 2 becomes 40Ω according to the conventional duobinary transmitter standard.

A receiving voltage Vr at the receiving node Nr can be calculated through DC analysis.

According to the DC analysis, the receiving voltage Vr at the level 2 becomes VDD, the receiving voltage Vr at the level 1 becomes 2/3 VDD, and the receiving voltage Vr at the level 0 becomes 4/10 VDD.

Accordingly, an interval between the level 2 and the level 1 is 10/30 VDD, and an interval between the level 1 and the level 0 is 8/30 VDD, and thus the intervals between the three levels are not equal to each other.

As described above, in the conventional transmitter, the intervals between the three levels of the duobinary signal are not constant, and thus there is a problem that a large amount of bit errors occur during a reception operation.

In accordance with an embodiment of the present disclosure, a transmitter configured to provide a duobinary signal corresponding to one of level 0, level 1, and level 2 based on a first data and a second data may include a pull-up driving circuit including a plurality of pull-up resistors selectively coupled between a first power source and a transmission node according to the first data and the second data; and a pull-down driving circuit including a plurality of pull-down resistors selectively coupled between the transmission node and a second power source, wherein at least one of the plurality of pull-up resistors is coupled between the first power source and the transmission node both when the first data is activated and when the second data is activated, or at least one of the plurality of pull-down resistors is coupled between the second power source and the transmission node both when the first data is activated and when the second data is activated.

The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate various embodiments, and explain various principles and advantages of those embodiments.

FIG. 1 illustrates a conventional transmitter.

FIG. 2 illustrates a transmitter according to an embodiment of the present disclosure.

FIG. 3 illustrates a transmitter according to another embodiment of the present disclosure.

The following detailed description references the accompanying figures in describing illustrative embodiments consistent with this disclosure. The embodiments are provided for illustrative purposes and are not exhaustive. Additional embodiments not explicitly illustrated or described are possible. Further, modifications can be made to presented embodiments within the scope of teachings of the present disclosure. The detailed description is not meant to limit this disclosure. Rather, the scope of the present disclosure is defined in accordance with claims and equivalents thereof. Also, throughout the specification, reference to “an embodiment” or the like is not necessarily to only one embodiment, and different references to any such phrase are not necessarily to the same embodiment(s).

FIG. 2 is a circuit diagram showing a transmitter 100 according to an embodiment of the present disclosure.

The transmitter 100 includes a pull-up driving circuit 110 and a pull-down driving circuit 120 .

The pull-up driving circuit 110 is coupled between a first power source VDD and a transmission node Nt, and the pull-down driving circuit 120 is coupled between the transmission node Nt and a second power source GND.

The pull-up driving circuit 110 includes a first PMOS transistor MP 1 and a second PMOS transistor MP 2 each having a gate to which first data D 1 is input and a source coupled to the first power source VDD, and a third PMOS transistor MP3 and a fourth PMOS transistor MP4 each having a gate to which second data D 2 is input and a source coupled to the first power source VDD.

The pull-up driving circuit 110 further includes a first pull-up resistor RU 1 coupled between a drain of the first PMOS transistor MP 1 and the transmission node Nt, a second pull-up resistor RU 2 coupled between a common drain of the second PMOS transistor MP 2 and the third PMOS transistor MP3 and the transmission node Nt, and a third pull-up resistor RU 3 coupled between a drain of the fourth PMOS transistor MP4 and the transmission node Nt.

The pull-down driving circuit 120 includes a first pull-down resistor RD 1 and a second pull-down resistor RD 2 each having a first node coupled to the transmission node Nt.

The pull-down driving circuit 120 further includes a first NMOS transistor MN 1 coupled between a second node of the first pull-down resistor RD 1 and the second power source GND and having a gate to which the first data D 1 is input.

The pull-down driving circuit 120 further includes a second NMOS transistor MN 2 coupled between a second node of the second pull-down resistor RD 2 and the second power source GND and having a gate to which the second data D 2 is input.

A channel 3 having a shape of a microstrip or the like is positioned between the transmission node Nt and a receiving node Nr.

A receiver 2 includes a termination resistor Rt coupled between the first power supply VDD and the receiving node Nr.

In FIG. 2 , a duobinary signal corresponds to level 2 when both the first data D 1 and the second data D 2 are at a low level, the duobinary signal corresponds to level 1 when only one of the first data D 1 and the second data D 2 is at the low level, and the duobinary signal corresponds to level 0 when both the first data D 1 and the second data D 2 are at a high level.

In this embodiment, it is assumed that resistance of the termination resistor Rt is 60Ω.

In this embodiment, resistance of the first pull-up resistor RU 1 is the same as resistance of the third pull-up resistor RU 3 , and resistance of the first pull-down resistor RD 1 is the same as resistance of the second pull-down resistor RD 2 .

Also, the resistance of the first pull-up resistor RU 1 is different from resistance of the second pull-up resistor RU 2 .

Unlike the conventional transmitter 1 shown in FIG. 1 , the transmitter 100 according to the present embodiment further includes the second pull-up resistor RU 2 in the pull-up driving circuit 110 . At the level 1, the second pull-up resistor RU 2 is additionally coupled between the first power source VDD and the transmission node Nt, so that the intervals between the levels of the duobinary signal become equal to each other. That is, the level 1 is disposed in the middle of the level 0 and the level 2.

In this embodiment, the resistance of each of the first pull-up resistor RU 1 and the third pull-up resistor RU 3 is 240Ω and the resistance of the second pull-up resistor RU 2 is 120Ω, making total pull-up resistance be 60Ω.

In addition, it is assumed that the resistance of each of the first pull-down resistor RD 1 and the second pull-down resistor RD 2 is 80Ω in order to make the total pull-down resistance be 40Ω.

A receiving voltage Vr of the receiving node Nr can be calculated through DC analysis.

In this embodiment, the receiving voltage Vr of the receiving node Nr at the level 2 is VDD, the receiving voltage Vr at the level 1 is 7/10 VDD, and the receiving voltage Vr at the level 0 is 4/10 VDD.

In this case, the interval between the level 2 and the level 1 and the interval between the level 1 and the level 0 are the same as 3/10 VDD.

As described above, in the present embodiment, by simply modifying the pull-up driving circuit 110 , the interval between the level 2 and the level 1 of the duobinary signal can be equal to the interval between the level 1 and the level 0.

FIG. 3 is a circuit diagram showing a transmitter 200 according to another embodiment of the present disclosure.

The transmitter 200 includes a pull-up driving circuit 210 and a pull-down driving circuit 220 .

The pull-up driving circuit 210 is coupled between a first power source VDD and the transmission node Nt, and the pull-down driving circuit 220 is coupled between the transmission node Nt and a second power source GND.

The pull-up driving circuit 210 includes a first pull-up resistor RU 1 and a second pull-up resistor RU 2 each having a first node coupled to a transmission node Nt.

The pull-up driving circuit 210 further includes a first PMOS transistor MP 1 having a drain coupled to a second node of the first pull-up resistor RU 1 , a source coupled to the first power source VDD, and a gate receiving first data D 1 .

The pull-up driving circuit 210 further includes a second PMOS transistor MP 2 having a drain coupled to a second node of the second pull-up resistor RU 2 , a source coupled to the first power source VDD, and a gate receiving second data D 2 .

The pull-down driving circuit 220 includes a first pull-down resistor RD 1 , a second pull-down resistor RD 2 , and a third pull-down resistor RD 3 each having a first node coupled to the transmission node Nt.

The pull-down driving circuit 220 further includes a first NMOS transistor MN 1 having a drain coupled to a second node of the first pull-down resistor RD 1 , a source coupled to the second power source GND, and a gate receiving the first data D 1 .

The pull-down driving circuit 220 further includes a second NMOS transistor MN 2 having a drain coupled to a second node of the second pull-down resistor RD 2 , a source coupled to the second power source GND, and a gate receiving the first data D 1 .

The pull-down driving circuit 220 further includes a third NMOS transistor MN 3 having a drain coupled to the second node of the second pull-down resistor RD 2 , a source coupled to the second power source GND, and a gate receiving the second data D 2 .

The pull-down driving circuit 220 further includes a fourth NMOS transistor MN 4 having a drain coupled to a second node the third pull-down resistor RD 3 , a source coupled to the second power source GND, and a gate receiving the second data D 2 .

A channel 3 having a shape of a microstrip or the like is positioned between the transmission node Nt and a receiving node Nr.

A receiver 4 includes a termination resistor Rt connected between the second power source GND and the receiving node Nr.

In FIG. 3 , a duobinary signal corresponds to level 2 when both the first data D 1 and the second data D 2 are at a low level, the duobinary signal corresponds to level 1 when only one of the first data D 1 and the second data D 2 is at a high level, and the duobinary signal corresponds to level 0 when both the first data D 1 and the second data D 2 are at the high level.

In the embodiment of FIG. 3 , it is assumed that resistance of the termination resistor Rt is 60Ω.

In the embodiment of FIG. 3 , resistance of the first pull-up resistor RU 1 is the same as resistance of the second pull-up resistor RU 2 , and resistance of the first pull-down resistor RD 1 is the same as resistance of the third pull-down resistor RD 3 .

Also, the resistance of the first pull-down resistor RD 1 is different from resistance of the second pull-down resistor RD 2 .

Unlike the conventional transmitter 1 shown in FIG. 1 , the transmitter 200 according to the present embodiment further includes the second pull-down resistor RD 2 in the pull-down driving circuit 220 . At the level 1, the second pull-down resistor RD 2 is additionally coupled between the second power source GND and the transmission node Nt, so that the intervals between the levels of the duobinary signal become equal to each other. That is, the level 1 is disposed in the middle of the level 0 and the level 2.

In the embodiment of FIG. 3 , it is assumed that resistance of each of the first pull-up resistor RU 1 and the second pull-up resistor RU 2 is 80Ω in order to make the total pull-up resistance be 40Ω.

In addition, it is assumed that resistance of each of the first pull-down resistor RD 1 and the third pull-down resistor RD 3 is 240Ω and resistance of the second pull-down resistor RD 2 is 120Ω in order to make the total pull-down resistance be 60Ω.

A receiving voltage Vr of the receiving node Nr can be calculated through the DC analysis.

In the embodiment of FIG. 3 , the receiving voltage Vr of the receiving node Nr at the level 2 is 6/10 VDD, the receiving voltage Vr at the level 1 is 3/10 VDD, and the receiving voltage Vr at the level 0 is 0.

In this case, the interval between the level 2 and the level 1 and the interval between the level 1 and the level 0 are the same as 3/10 VDD.

As described above, by simply modifying the pull-down driving circuit 220 , the interval between the level 2 and the level 1 of the duobinary signal can be equal to the interval between the level 1 and the level 0.

Through this, in the present invention, the quality of a transmitted duobinary signal can be improved.

Although various embodiments have been illustrated and described, various changes and modifications may be made to the described embodiments without departing from the spirit and scope of the invention as defined by the following claims.