Asymmetrically terminated PAM-4 transmission driver

Abstract

According to an embodiment of the present invention, an asymmetrically terminated PAM-4 transmission driver may comprise: first to third pull-up circuits including a plurality of transistors; first to third pull-down circuits connected in parallel to the first to third pull-up circuits, respectively, and including a plurality of transistors; and a controller for adjusting the magnitudes of impedances of the first to third pull-up circuits and the magnitudes of impedances of the first to third pull-down circuits so that an output impedance of the asymmetrically terminated PAM-4 transmission driver matches identically to the impedance of a channel connected to the terminated PAM-4 transmission driver.

Description

Asymmetric Ended PAM-4 Transmission Driver

[0001] The present invention relates to an asymmetric termination PAM-4 transmission driver, and more specifically, to an asymmetric termination PAM-4 transmission driver with an improved structure that enables high-speed operation by enhancing the output swing of a transmission driver that outputs a multi-level signal.

[0002] With the development of information and communication technology, there is a growing need for drivers capable of transmitting vast amounts of data at high speeds.

[0003] To achieve high-speed transmission of such large-capacity data, PAM 4 (Four-Level Pulse Amplitude Modulation) technology, which can transmit 2-bit signals at a time instead of 1-bit, is being applied in signal processing fields requiring high-speed operation, such as ultra-high-speed wired / wireless communication ICs, communication units of processing units like CPUs / GPUs, and memory-CPU communication units, in order to increase signal transmission efficiency. Unlike the conventionally used PAM 2 signal, PAM 4 signals can transmit data corresponding to 2 bits at a time, which has the advantage of increasing data transmission speed and efficiency.

[0004] However, in the case of conventional transmission drivers that output multi-level signals, there is a problem in which the signal-to-noise ratio (SNR) deteriorates as the eye opening decreases depending on the modulation of the output.

[0005] To solve this problem, the amplitude of the overall output was improved by using a POD (Pseudo Open Drain) interface, but there was a problem with unstable amplitude between each eye opening of the eye diagram. As a result, the Level Separation Mismatch Ratio (RLM) was reduced, leading to a problem where the Bit Error Rate (BER) decreased during data reception.

[0006] In addition, as the output impedance changes according to variations in the transmission driver's output, a problem arises that causes signal degradation due to the mismatch in output impedance.

[0007] Accordingly, the asymmetric termination PAM-4 transmission driver according to the disclosed invention is an invention created to solve the aforementioned problems, and its purpose is to provide a technology capable of increasing the overall output swing by configuring the PAM-4 transmission driver with asymmetrically terminated pull-up and pull-down circuits.

[0008] More specifically, the asymmetric termination PAM-4 transmission driver according to the disclosed invention is intended to enable the PAM-4 transmission driver to operate at high speed by improving the eye opening and SNR (Signal to Noise Ratio) by increasing the output swing by adjusting the output impedance of the transmission driver.

[0009] An asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention may include a first to third pull-up circuit comprising a plurality of transistors, a first to third pull-down circuit connected in parallel with the first to third pull-up circuits and comprising a plurality of transistors, and a control unit that adjusts the magnitudes of the first to third pull-up circuits and the first to third pull-down circuits so that the output impedance of the asymmetric termination PAM-4 transmission driver is matched to the same as the impedance of a channel connected to the termination PAM-4 transmission driver.

[0010] The above control unit can adjust the magnitude of the output impedance of the asymmetrical end PAM-4 transmission driver based on the output data of the asymmetrical end PAM-4 transmission driver.

[0011] The above control unit may have a plurality of impedance modes based on the output data of the asymmetric termination PAM-4 transmission driver.

[0012] The above plurality of impedance modes can operate in a first impedance mode in which the first to third pull-up circuits are turned OFF and the first to third pull-down circuits are turned ON.

[0013] The above plurality of impedance modes can operate in a second impedance mode in which the first to second pull-up circuits and the third pull-down circuit are turned OFF, and the third pull-up circuit and the first to second pull-down circuits are turned ON.

[0014] The above plurality of impedance modes can operate in a third impedance mode in which the first pull-up circuit and the second to third pull-down circuits are turned OFF, and the second to third pull-up circuits and the first pull-down circuit are turned ON.

[0015] The above plurality of impedance modes can operate in a fourth impedance mode in which the first to third pull-down circuits are turned OFF and the first to third pull-up circuits are turned ON.

[0016] The control unit can adjust the impedances of the first to third pull-up circuits and the first to third pull-down circuits so that the magnitudes of the impedances of the first to third pull-up circuits and the magnitudes of the impedances of the first to third pull-down circuits are set differently.

[0017] The control unit above has the impedances of the first to second pull-up circuits and the first to second pull-down circuits having the same impedance magnitude, and the impedance of the third pull-down circuit may have the lowest impedance magnitude.

[0018] An asymmetric termination PAM-4 transmission driver according to another embodiment of the disclosed invention comprises a first to third pull-up circuit including a plurality of transistors, a first to third pull-down circuit connected in parallel with the first to third pull-up circuits and including a plurality of transistors, and a control unit that adjusts the magnitude of the impedance of the first to third pull-up circuits and the first to third pull-down circuits to determine the output swing of the asymmetric termination PAM-4 transmission driver, and the asymmetric termination PAM-4 transmission driver can receive binary input data converted into a thermometer code by an encoder.

[0019] The above control unit may have a plurality of impedance modes based on the output swing of the asymmetric termination PAM-4 transmission driver.

[0020] The above plurality of impedance modes may operate in one of the following modes: a first impedance mode in which the first to third pull-up circuits are OFF and the first to third pull-down circuits are ON; a second impedance mode in which the first to third pull-up circuits and the third pull-down circuit are OFF and the first to second pull-down circuits are ON; a third impedance mode in which the first pull-up circuit, the third pull-up circuit, and the second to third pull-down circuits are OFF and the second pull-up circuit and the first pull-down circuit are ON; or a fourth impedance mode in which the third pull-up circuit and the first to third pull-down circuits are OFF and the first to second pull-up circuits are ON.

[0021] The control unit can adjust the impedances of the first to third pull-up circuits and the first to third pull-down circuits so that the magnitudes of the impedances of the first to third pull-up circuits and the magnitudes of the impedances of the first to third pull-down circuits are set differently.

[0022] The control unit above has the impedances of the first to second pull-up circuits and the first to second pull-down circuits having the same impedance magnitude, and the impedance of the third pull-down circuit may have the lowest impedance magnitude.

[0023] An asymmetric termination PAM-4 transmission driver according to another embodiment of the disclosed invention may include a first to third pull-up circuit comprising a plurality of transistors, a first to third pull-down circuit connected in parallel with the first to third pull-up circuits and comprising a plurality of transistors, and a control unit that adjusts the impedances of the first to third pull-up circuits and the first to third pull-down circuits such that the magnitudes of the impedances of the first to third pull-up circuits and the magnitudes of the impedances of the first to third pull-down circuits are set differently.

[0024] Accordingly, the asymmetric termination PAM-4 transmission driver according to the disclosed invention is an invention created to solve the aforementioned problems, and by configuring the PAM-4 transmission driver as an asymmetrically terminated circuit, it is possible to improve the overall output swing while simultaneously securing high linearity between output levels with a uniform eye height.

[0025] In addition, the mismatch between the output impedance and the channel impedance of the transmission driver can be minimized.

[0026] Therefore, unlike conventional technology, it has the advantage of enabling high-speed operation with improved eye opening and SNR.

[0027] Figure 1 is a diagram showing the structure of a POD interface according to the prior art.

[0028] FIG. 2 is a diagram showing a multi-level transmission driver according to the prior art.

[0029] Figure 3 is a diagram showing an impedance-asymmetric PAM-4 transmission driver according to the prior art.

[0030] FIG. 4 is a diagram illustrating a data system including an asymmetric termination PAM-4 transmission driver according to one embodiment of the present invention.

[0031] Figure 5 is a drawing showing an encoder according to Figure 4.

[0032] FIG. 6 is a diagram showing an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention.

[0033] FIG. 7 is a diagram showing the impedance operation of an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention.

[0034] Figure 8 is a diagram showing the final impedance when operating according to Figure 7.

[0035] FIG. 9 is a diagram showing the impedance operation of an asymmetric termination PAM-4 transmission driver according to another embodiment of the disclosed invention.

[0036] Figure 10 is a diagram showing the final impedance when operated according to Figure 9.

[0037] FIG. 11 is a diagram showing the step response simulation results of an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention.

[0038] FIGS. 12 and 13 are diagrams comparing the eye diagrams of a conventional PAM-4 transmission driver and an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention.

[0039] The embodiments described in this specification and the configurations illustrated in the drawings are merely preferred examples of the disclosed invention, and various modifications that may replace the embodiments and drawings of this specification may exist at the time of filing this application.

[0040] Additionally, the same reference numerals or symbols presented in each drawing of this specification represent parts or components that perform substantially the same function.

[0041] Furthermore, the terms used herein are for describing embodiments and are not intended to limit or / or restrict the disclosed invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0042] In this specification, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and do not preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0043] Additionally, terms including ordinal numbers, such as "first," "second," etc., used in this specification may be used to describe various components, but said components are not limited by said terms, and said terms are used solely for the purpose of distinguishing one component from another.

[0044] For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0045] Hereinafter, embodiments according to the present invention will be described in detail with reference to the attached drawings.

[0046] FIG. 1 is a diagram showing the structure of a POD interface according to the prior art. FIG. 2 is a diagram showing a multi-level transmission driver according to the prior art.

[0047] Referring to FIG. 1, a transmission driver of a POD interface structure according to the prior art has the output impedance of a pull-down circuit as the termination resistor (R) of the receiver. RXBy designing it to be lower than ), the output circuit's low voltage was lowered to improve the SNR and increase the output amplitude.

[0048] Referring to FIG. 2, a multi-level transmission driver according to the prior art is composed of a plurality of pull-up circuits and pull-down circuits and can output a multi-level signal.

[0049] At this time, in order to maintain the integrity of the signal, the characteristic impedance (Z0) of the channel is equal to the output impedance (Z) of the transmitter. TX ) and the terminal impedance (Z RX It can operate by matching with ).

[0050] PAM-4 transmission drivers based on such conventional technology suffered from a problem where the SNR decreased as each eye opening decreased depending on the modulation level of the output.

[0051] Figure 3 shows that to solve the problems associated with the conventional technology, a conventional POD interface structure is combined with a conventional multi-level transmission driver to improve the output amplitude.

[0052] Referring to Fig. 3, the impedances of the pull-up and pull-down circuits of the multi-level transmission driver are designed to be asymmetrical to improve the overall output amplitude of the transmission driver.

[0053] However, a problem occurred in which the intermediate level voltage was not formed linearly. As a result, the amplitude of each eye opening was unstable, causing the Level Separation Mismatch Ratio (RLM) to decrease, which in turn caused a problem of the Bit Error Rate (BER) decreasing during data reception.

[0054] In addition, this caused a problem where the output impedance of the transmission driver gradually changed according to the output level, leading to signal degradation due to impedance mismatch.

[0055] Therefore, in order to solve the problems of the transmission driver according to the aforementioned conventional technology, a transmission driver was needed that could improve the signal-to-noise ratio (SNR) while simultaneously increasing the overall output amplitude.

[0056] To solve the aforementioned problems, an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention proposes an asymmetric termination PAM-4 transmission driver capable of operating at high speed by improving the eye opening and SNR (Signal to Noise Ratio) by increasing the output swing through adjusting the output impedance of the transmission driver.

[0057] Hereinafter, an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention will be described in detail.

[0058] FIG. 4 is a diagram illustrating a data system including an asymmetric termination PAM-4 transmission driver according to one embodiment of the present invention.

[0059] Referring to FIG. 4, a data system (100) including the present invention can have a transmitter (140) and a receiver (160) that include a serializer (110), an encoder (120), and an asymmetric end PAM-4 transmission driver (130) communicate through a channel (150).

[0060] The encoder (120) is configured as a binary-to-thermometer encoder and can generate a thermometer code corresponding to a binary signal and provide it as an input to an asymmetric end PAM-4 transmission driver (130).

[0061] Specifically, the binary-to-thermometer encoder can be implemented using CMOS logic circuits, etc., as shown in FIG. 5.

[0062] In addition, the thermometer code based on the binary signal can be set as shown in [Table 1] below.

[0063] QuaternaryBinaryThermometerMSBLSBD <0> D <1> D <2> 000111101110210100311000

[0064]

[0065] FIG. 6 is a diagram showing an asymmetric termination PAM-4 transmission driver according to one embodiment of the present invention.

[0066] Referring to FIG. 6, an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention may be configured such that a first pull-up circuit to a third pull-up circuit (131 to 133) comprising a plurality of transistors and a first pull-down circuit to a third pull-down circuit (134 to 136) comprising a plurality of transistors are connected in parallel.

[0067] Additionally, an asymmetric end-terminated PAM-4 transmission driver (130) according to one embodiment of the disclosed invention can be connected to a channel (150) and communicate with a receiver (160).

[0068] Specifically, the output impedance (Z) of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention TX The impedance magnitude of the first to third pull-up circuits (131 to 133) and the first to third pull-down circuits (134 to 136) can be controlled by a control unit (not shown) so that they have the same impedance magnitude as the channel impedance (Z0) of the channel (150).

[0069] Additionally, based on the output data of the asymmetric end PAM-4 transmission driver (130) according to one embodiment of the disclosed invention, the magnitude of the output impedance of the asymmetric end PAM-4 transmission driver (130) can be adjusted by a control unit (not shown).

[0070] At this time, the output data of the asymmetric end PAM-4 transmission driver (130) according to one embodiment of the disclosed invention can be determined by the following equations.

[0071] Equation (1)

[0072]

[0073] (2)

[0074]

[0075] Here, R PU,ON and R PD,ON is the impedance of the first to third pull-up circuits (131~133) and the first to third pull-down circuits (134~136) that are turned ON, and Z TX is the output impedance of the transmission driver (130), Z0 is the channel impedance of the channel (150), and R RX is the terminal impedance of the receiver (160).

[0076] Specifically, the output impedance (Z) of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention TX In order to maintain linearity of the output voltage while achieving a uniform eye opening and having the same impedance as the channel impedance (Z0), it can be organized as shown in [Table 2] below based on the above equations (1) and (2).

[0077]

[0078] Here, A represents the output swing value to be achieved.

[0079] FIG. 7 is a diagram showing the impedance operation of an asymmetric termination PAM-4 transmission driver according to one embodiment of the present invention. FIG. 8 is also a diagram showing the final impedance when operating according to FIG. 7.

[0080] Referring to FIG. 7, a plurality of impedance modes can be controlled by a control unit (not shown) based on the output data of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention.

[0081] Specifically, in the case of a first impedance mode in which the asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention outputs '0', the first to third pull-up circuits (131 to 133) may be turned OFF, and the first to third pull-down circuits (134 to 136) may be operated to be turned ON.

[0082] Additionally, in the case of a second impedance mode that outputs '1', the first to second pull-up circuits (131~132) and the third pull-down circuit (136) may be turned OFF, and the third pull-up circuit (133) and the first to second pull-down circuits (134~135) may be operated to be turned ON.

[0083] Additionally, in the case of the third impedance mode that outputs '2', the first pull-up circuit (131) and the second to third pull-down circuits (135~136) can be turned OFF, and the second to third pull-up circuits (132~133) and the first pull-down circuit (134) can be operated to be turned ON.

[0084] In addition, in the case of the fourth impedance mode that outputs '3', the first to third pull-down circuits (134~136) can be operated to be OFF, and the first to third pull-up circuits (131~133) can be operated to be ON.

[0085] In addition, the impedance of the first to third pull-up circuits (131 to 133) and the impedance of the first to third pull-down circuits (134 to 136) can be adjusted by a control unit (not shown) so that they are set differently.

[0086] In addition, the impedances of the first pull-up circuit to the second pull-up circuit (131 to 132) and the first pull-down circuit to the second pull-down circuit (134 to 135) may have the same impedance magnitude.

[0087] Additionally, the impedance of the third pull-down circuit (136) may have the lowest impedance magnitude among the magnitudes of the respective impedances of the first to third pull-up circuits (131 to 133) and the first to second pull-down circuits (134 to 135).

[0088] For example, the channel impedance (Z0) of the channel (150) and the terminal impedance (R) of the receiver (160) RX In the case where an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the invention disclosed for 60 ohms is to achieve a total output swing value of 0.6, it may be configured to operate as follows.

[0089] When operating in the first impedance mode, only the pull-down circuits (134~136) operate to achieve a low output level, and the output impedance (Z) of the transmitter (150) RX ) may not match the channel impedance (Z0) of the channel (150). Accordingly, according to [Table 2] above, the output voltage level of the first mode is 0.4*V DDQ It becomes, and the output impedance (Z RX ) is 2 / 3*R RX It can be.

[0090] In addition, when operating in the second impedance mode, the output voltage level is 0.6*V according to [Table 2] above. DDQ It becomes, and the output voltage level when operating in third impedance mode is 0.8*V DDQ It becomes, and the output voltage level when operating in fourth impedance mode is 1.0*V DDQ It can be.

[0091] At this time, when operating in the second to fourth impedance mode, the output impedance (Z) of the asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention RX ) can be matched to the channel impedance (Z0) of the channel (150).

[0092] Referring to FIG. 8, the channel impedance (Z0) of the channel (150) and the terminal impedance (R) of the receiver (160) RX 0.6*V when ) is 60 ohms DDQ When attempting to achieve this, the first pull-up circuit to the second pull-up circuit (131–132) and the first pull-down circuit to the second pull-down circuit (134–135) may be configured to 150 ohms.

[0093] Additionally, the third pull-up circuit (133) may be configured to 300 ohms, and the third pull-down circuit (136) may be configured to 85.71 ohms.

[0094] Accordingly, the asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention has an improved overall output amplitude compared to the prior art, and at the same time, 0.2*V DDQ SNR can be improved through uniform eye opening.

[0095] FIG. 9 is a diagram showing the impedance operation of an asymmetric termination PAM-4 transmission driver according to another embodiment of the disclosed invention. Also, FIG. 10 is a diagram showing the final impedance when operating according to FIG. 8.

[0096] Referring to FIG. 9, an asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention may be configured such that a first pull-up circuit to a third pull-up circuit (131 to 133) comprising a plurality of transistors and a first pull-down circuit to a third pull-down circuit (134 to 136) comprising a plurality of transistors are connected in parallel.

[0097] Additionally, an asymmetric end PAM-4 transmission driver (130) according to another embodiment of the disclosed invention can receive binary input data converted into a thermometer code by an encoder (120).

[0098] Additionally, an asymmetric end PAM-4 transmission driver (130) according to another embodiment of the disclosed invention can be connected to a channel (150) and communicate with a receiver (160).

[0099] In addition, to determine the output swing of the asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention, the impedance magnitudes of the first to third pull-up circuits (131 to 133) and the first to third pull-down circuits (134 to 136) can be controlled by a control unit (not shown).

[0100] At this time, the output data of the asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention can be determined by [Table 2].

[0101] For example, the channel impedance (Z0) of the channel (150) and the terminal impedance (R) of the receiver (160) RX In the case where an asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the invention disclosed for 50 ohms is to achieve a total output swing value of 0.75, it may be configured to operate as follows.

[0102] Referring to FIG. 9, a plurality of impedance modes can be controlled by a control unit (not shown) based on the output data of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention.

[0103] Specifically, in the case of a first impedance mode that outputs '0', the first to third pull-up circuits (131 to 133) can be controlled to be OFF, and the first to third pull-down circuits (134 to 136) can be controlled to be ON. Additionally, in the case of a second impedance mode that outputs '1', the first to third pull-up circuits (131 to 133) and the third pull-down circuit (136) can be controlled to be OFF, and the first to second pull-down circuits (134 to 135) can be operated to be ON.

[0104] Additionally, in the case of the third impedance mode that outputs '2', the first pull-up circuit (131), the third pull-up circuit (133), and the second to third pull-down circuits (135 to 136) can be turned OFF, and the second pull-up circuit (132) and the first pull-down circuit (134) can be operated to be turned ON.

[0105] Additionally, in the case of the fourth impedance mode that outputs '3', the third pull-up circuit (133) and the first to third pull-down circuits (134 to 136) can be operated to be OFF, and the first to second pull-up circuits (131 to 132) can be operated to be ON.

[0106] At this time, when operating in the first impedance mode, only the pull-down circuits (134~136) operate, and according to [Table 2] above, the output voltage level of the first mode is 0.25*V DDQ It becomes, and the output impedance (Z RX ) is 1 / 3*R RX It can be.

[0107] In addition, when operating in the second impedance mode, the output voltage level is 0.5*V according to [Table 2] above. DDQ It becomes, and the output voltage level when operating in third impedance mode is 0.75*V DDQ It becomes, and the output voltage level when operating in fourth impedance mode is 1.0*V DDQ It may be, and the output impedance (Z) of the asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention RX ) can be matched to the channel impedance (Z0) of the channel (150).

[0108] Referring to FIG. 10, when an asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention operates in one of the first to fourth impedance modes, the magnitudes of the impedances of the first to third pull-up circuits (131 to 133) and the magnitudes of the impedances of the first to third pull-down circuits (134 to 136) may be set differently.

[0109] In addition, the impedances of the first pull-up circuit to the second pull-up circuit (131 to 132) and the first pull-down circuit to the second pull-down circuit (134 to 135) may have the same impedance magnitude.

[0110] Additionally, the impedance of the third pull-down circuit (136) may have the lowest impedance magnitude among the magnitudes of the respective impedances of the first to third pull-up circuits (131 to 133) and the first to second pull-down circuits (134 to 135).

[0111] For example, the channel impedance (Z0) of the channel (150) and the terminal impedance (R) of the receiver (160) RX 0.75*V when ) is 50 ohms DDQ When attempting to achieve this, the first pull-up circuit to the second pull-up circuit (131–132) and the first pull-down circuit to the second pull-down circuit (134–135) may be configured to be 100 ohms.

[0112] Additionally, the third pull-down circuit (136) may be configured to have 25 ohms. At this time, the third pull-up circuit (133) may be configured to have an infinite impedance so that it is always OFF.

[0113] Accordingly, the asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention is 0.25*V DDQ SNR can be improved through uniform eye opening.

[0114] An asymmetric termination PAM-4 transmission driver (130) according to another embodiment of the disclosed invention may be configured such that a first pull-up circuit to a third pull-up circuit (131 to 133) comprising a plurality of transistors and a first pull-down circuit to a third pull-down circuit (134 to 136) comprising a plurality of transistors are connected in parallel.

[0115] In addition, in another embodiment of the disclosed invention, the asymmetric termination PAM-4 transmission driver (130) may have the impedance magnitudes of the first to third pull-up circuits (131 to 133) set differently from the impedance magnitudes of the first to third pull-down circuits (134 to 136) by a control unit (not shown).

[0116] FIG. 11 is a diagram showing the step response simulation results of an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention.

[0117] Referring to FIG. 11, the step response simulation result of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention shows that the total output amplitude is 600mV at a power supply of 1.0V.

[0118] In addition, when the RLM (Level separation Mismatch Ratio) is defined as the interval between output signal levels corresponding to each input data A, B, and C as shown in Equation (3) below, it can be confirmed that an RLM of 99% or more has been achieved.

[0119] Equation (3)

[0120]

[0121] FIGS. 12 and 13 are diagrams comparing the eye diagrams of a conventional PAM-4 transmission driver and an asymmetric termination PAM-4 transmission driver according to one embodiment of the disclosed invention.

[0122] Referring to FIG. 12, the channel impedance (Z) of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the invention disclosed by FIG. 7 o The terminal impedance (R) of the receiver (160) RX 0.6*V when ) is 60 ohms DDQ This is an eye diagram comparing the achievement with the conventional PAM-4 transmission driver.

[0123] Specifically, the overall output swing is increased by the asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention, so that the voltage margin of each eye is increased by about 1.14 times compared to the prior art and can be increased by up to about 1.58 times. Accordingly, the SNR can be improved by about 1.141 dB to 1.58 dB.

[0124] Referring to FIG. 13, the channel impedance (Z) of an asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the invention disclosed by FIG. 9 o The terminal impedance (R) of the receiver (160) RX 0.75*V when ) is 50 ohms DDQ This is an eye diagram comparing the achievement with the conventional PAM-4 transmission driver.

[0125] Specifically, the overall output swing is increased by the asymmetric termination PAM-4 transmission driver (130) according to one embodiment of the disclosed invention, so that the voltage margin of each eye is increased by about 1.5 times compared to the prior art and can be increased by up to about 3.52 times. Accordingly, the SNR can be improved by about 1.5 dB to 3.52 dB.

[0126] The device described above may be implemented as a hardware component, a software component, and / or a combination of a hardware component and a software component. For example, the device and components described in the embodiments may be implemented using one or more general-purpose or special-purpose computers, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing unit may execute an operating system (OS) and one or more software applications executed on the operating system. Additionally, the processing unit may access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processing unit may be described as being used as a single unit, but those skilled in the art will understand that the processing unit may include multiple processing elements and / or multiple types of processing elements. For example, the processing unit may include multiple processors or one processor and one controller. In addition, other processing configurations, such as parallel processors, are also possible.

[0127] Software may include computer programs, code, instructions, or a combination of one or more of these, and may configure a processing unit to operate as desired or instruct the processing unit independently or collectively. Software and / or data may be embodied in any type of machine, component, physical device, virtual equipment, computer storage medium, or device so as to be interpreted by the processing unit or to provide instructions or data to the processing unit. Software may be distributed over networked computer systems and may be stored or executed in a distributed manner. Software and data may be stored on one or more computer-readable recording media.

[0128] The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the medium may be those specifically designed and configured for the embodiment, or they may be those known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

[0129] Although the embodiments have been described above with reference to limited examples and drawings, those skilled in the art can make various modifications and variations from the description above. For example, suitable results may be achieved even if the described techniques are performed in a different order than described, and / or if the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents. Therefore, other implementations, other embodiments, and equivalents to the claims below are also within the scope of the claims.

Claims

1. The asymmetric terminated PAM-4 transmission driver is, A first to third pull-up circuit comprising a plurality of transistors; A first pull-down circuit to a third pull-down circuit connected in parallel with the first to third pull-up circuits and comprising a plurality of transistors; and A control unit for adjusting the magnitudes of the impedances of the first to third pull-up circuits and the first to third pull-down circuits so that the output impedance of the asymmetric termination PAM-4 transmission driver is matched identically to the impedance of the channel connected to the termination PAM-4 transmission driver; characterized by including Asymmetric Ended PAM-4 Transmission Driver.

2. In Paragraph 1, The above control unit is, Characterized by adjusting the magnitude of the output impedance of the asymmetrical-ended PAM-4 transmission driver based on the output data of the asymmetrical-ended PAM-4 transmission driver. Asymmetric Ended PAM-4 Transmission Driver.

3. In Paragraph 2, The above control unit is, Characterized by having a plurality of impedance modes based on the output data of the above-mentioned asymmetric termination PAM-4 transmission driver, Asymmetric Ended PAM-4 Transmission Driver.

4. In Paragraph 3, The above plurality of impedance modes are, Characterized by including a first impedance mode in which the first to third pull-up circuits are OFF and the first to third pull-down circuits are ON. Asymmetric Ended PAM-4 Transmission Driver.

5. In Paragraph 3, The above plurality of impedance modes are, Characterized by including a second impedance mode in which the first to second pull-up circuits and the third pull-down circuit are OFF, and the third pull-up circuit and the first to second pull-down circuits are ON. Asymmetric Ended PAM-4 Transmission Driver.

6. In Paragraph 3, The above plurality of impedance modes are, Characterized by including a third impedance mode in which the first pull-up circuit and the second to third pull-down circuits are OFF, and the second to third pull-up circuits and the first pull-down circuit are ON. Asymmetric Ended PAM-4 Transmission Driver.

7. In Paragraph 3, The above plurality of impedance modes are, Characterized by including a fourth impedance mode in which the first to third pull-down circuits are OFF and the first to third pull-up circuits are ON. Asymmetric Ended PAM-4 Transmission Driver.

8. In Paragraph 2, The above control unit is, Characterized by adjusting the impedances of the first to third pull-up circuits and the first to third pull-down circuits so that the magnitudes of the impedances of the first to third pull-up circuits and the magnitudes of the impedances of the first to third pull-down circuits are set differently. Asymmetric Ended PAM-4 Transmission Driver.

9. In Paragraph 8, The above control unit is, The impedances of the first to second pull-up circuits and the first to second pull-down circuits have the same impedance magnitude, The impedance of the third pull-down circuit is characterized by having the lowest impedance magnitude. Asymmetric Ended PAM-4 Transmission Driver.

10. The asymmetric terminated PAM-4 transmission driver is, A first to third pull-up circuit comprising a plurality of transistors; A first pull-down circuit to a third pull-down circuit connected in parallel with the first to third pull-up circuits and comprising a plurality of transistors; and A control unit for adjusting the magnitudes of the impedances of the first to third pull-up circuits and the first to third pull-down circuits to determine the output swing of the above-mentioned asymmetric termination PAM-4 transmission driver; The above-mentioned asymmetric end PAM-4 transmission driver is characterized by receiving binary input data converted into a thermometer code by an encoder. Asymmetric Ended PAM-4 Transmission Driver.

11. In Paragraph 10, The above control unit is, Characterized by having a plurality of impedance modes based on the output swing of the above-mentioned asymmetric termination PAM-4 transmission driver, Asymmetric Ended PAM-4 Transmission Driver.

12. In Paragraph 11, The above plurality of impedance modes are, A first impedance mode in which the first to third pull-up circuits are OFF and the first to third pull-down circuits are ON; A second impedance mode in which the first to third pull-up circuits and the third pull-down circuit are OFF, and the first to second pull-down circuits are ON; A third impedance mode in which the first pull-up circuit, the third pull-up circuit, and the second to third pull-down circuits are OFF, and the second pull-up circuit and the first pull-down circuit are ON; and Characterized by including at least one of a fourth impedance mode in which the third pull-up circuit and the first to third pull-down circuits are OFF, and the first to second pull-up circuits are ON. Asymmetric Ended PAM-4 Transmission Driver.

13. In Paragraph 10, The above control unit is, Characterized by adjusting the impedances of the first to third pull-up circuits and the first to third pull-down circuits so that the magnitudes of the impedances of the first to third pull-up circuits and the magnitudes of the impedances of the first to third pull-down circuits are set differently. Asymmetric Ended PAM-4 Transmission Driver.

14. In Paragraph 13, The above control unit is, The impedances of the first to second pull-up circuits and the first to second pull-down circuits have the same impedance magnitude, The impedance of the third pull-down circuit is characterized by having the lowest impedance magnitude. Asymmetric Ended PAM-4 Transmission Driver.

15. The asymmetric terminated PAM-4 transmission driver is, A first to third pull-up circuit comprising a plurality of transistors; A first pull-down circuit to a third pull-down circuit connected in parallel with the first to third pull-up circuits and comprising a plurality of transistors; and A control unit for adjusting the impedances of the first to third pull-up circuits and the first to third pull-down circuits such that the magnitudes of the impedances of the first to third pull-up circuits and the magnitudes of the impedances of the first to third pull-down circuits are set differently; characterized by including Asymmetric Ended PAM-4 Transmission Driver.

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