Calibration circuit, method and device for terminal matching resistance

Abstract

This application relates to a calibration circuit, method, and apparatus for terminating matching resistors. The calibration circuit includes an AUX channel receiver, a first terminating resistor, a second terminating resistor, and a switching module. The switching module is electrically connected to the input of the AUX channel receiver and is used to switch between a first operating state and a second operating state. In the first operating state, the switching module configures the input of the AUX channel receiver to connect to a first connection point and a second connection point to perform AUX signal reception. In the second operating state, the switching module configures the input of the AUX channel receiver to connect to a common-mode node and a reference voltage terminal to perform calibration of the first and second terminating resistors. This allows for direct measurement and calibration of the first and second terminating resistors in actual use using external current and voltage sources.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a calibration circuit, method and apparatus for a terminating matching resistor. Background Technology

[0002] Both the main link and the AUX channel in the DisplayPort interface use differential signals for transmission. To ensure signal integrity and prevent signal reflection at the end of the transmission line, a precise 100Ω terminating resistor (RTN resistor) needs to be connected in parallel between the differential pairs (D+ and D-) at the receiving end. The accuracy of this resistor directly affects the signal eye diagram quality and the stable transmission of the link.

[0003] In traditional technology, there are two main methods for calibrating termination resistors (RTN resistors, or RTTs): one is to directly measure the resistance value of the differential signal channel. This method is simple to measure, but its accuracy is limited by external measuring instruments and it cannot calibrate the range of the on-chip adjustable resistors; the other is to integrate an independent resistor calibration circuit inside the chip and measure and calibrate the RTN resistor through a replication module. This method has a high degree of automation, but it calibrates the replication resistor rather than the actual resistor used, and it requires additional calibration circuitry, which occupies chip area. Summary of the Invention

[0004] Therefore, it is necessary to provide a calibration circuit, method, and device for a terminating matching resistor that simplifies the calibration process and saves chip area without adding a separate calibration circuit, in order to address the above-mentioned technical problems.

[0005] In a first aspect, this application provides a calibration circuit for a termination matching resistor, applied to a display interface, comprising: a receiver for an AUX channel, a first termination resistor, a second termination resistor, and a switch switching module. The first termination resistor and the second termination resistor are connected in series between a first connection point and a second connection point. The switch switching module is electrically connected to the input terminal of the receiver for the AUX channel and is used to switch between a first operating state and a second operating state.

[0006] In the first working state, the switch switching module is used to configure the input terminal of the receiver of the AUX channel to be connected to the first connection point and the second connection point, so as to perform the AUX signal receiving function;

[0007] In the second operating state, the switch switching module is used to configure the input terminal of the receiver of the AUX channel to be connected to the common mode node and the reference voltage terminal to perform the calibration function of the first terminating resistor and the second terminating resistor.

[0008] In one embodiment, in the second operating state, the calibration circuit further includes: an external current source and an external voltage source;

[0009] The external current source is connected to the first connection point through a first parasitic resistor;

[0010] The external voltage source is connected to the second connection point through a second parasitic resistor;

[0011] The first end of the first terminating resistor is connected to the first connection point, and the second end of the first terminating resistor is connected to the common-mode node.

[0012] The first end of the second terminating resistor is connected to the second connection point, and the second end of the second terminating resistor is connected to the common-mode node;

[0013] The first input terminal of the receiver of the AUX channel is connected to the common-mode node, and the second input terminal of the receiver of the AUX channel is connected to the reference voltage terminal.

[0014] In one embodiment, in the first operating state, the calibration circuit further includes: an internal common-mode voltage amplifier, the output of which is connected to the common-mode node, for providing a common-mode voltage to the first terminating resistor and the second terminating resistor;

[0015] The first connection point is connected to the positive terminal of the external AUX channel via a first parasitic resistor;

[0016] The second connection point is connected to the negative terminal of the external AUX channel via a second parasitic resistor;

[0017] The first end of the first terminating resistor is connected to the first input terminal of the receiver of the AUX channel and the first connection point, and the second end of the first terminating resistor is connected to the common mode node;

[0018] The first end of the second terminating resistor is connected to the second input terminal of the receiver of the AUX channel and the second connection point, and the second end is connected to the common mode node.

[0019] In one embodiment, in the first operating state, the internal common-mode voltage amplifier is connected to the common-mode node; in the second operating state, the internal common-mode voltage amplifier is disconnected from the common-mode node.

[0020] In one embodiment, in the second operating state, the voltage of the common-mode node is changed by successively adjusting the resistance value of the second terminating resistor.

[0021] In one embodiment, if the output of the receiver of the AUX channel flips, the voltage of the common-mode node is determined to be equal to the voltage of the internal reference voltage source, and the calibration value of the second terminating resistor is locked.

[0022] In one embodiment, the voltage at the first connection point is changed by successively adjusting the resistance value of the first terminal resistor;

[0023] If the voltage at the first connection point meets the preset conditions, the calibration value of the first terminating resistor is locked.

[0024] In one embodiment, the receiver of the AUX channel is configured as a high-precision comparator in the second operating state, and the output signal of the receiver of the AUX channel is used to indicate the magnitude relationship between the common-mode node voltage and the reference voltage.

[0025] Secondly, this application also provides a calibration method for a terminating matching resistor, wherein the calibration circuit of the terminating matching resistor described in any one of the first aspects is used to perform at least one of the following steps:

[0026] The calibration circuit is configured to the first working state by the switch switching module to perform the AUX signal receiving function;

[0027] The calibration circuit is configured to the second operating state by means of the switch switching module, and the calibration function of the first terminating resistor and the second terminating resistor is performed.

[0028] Thirdly, this application also provides a calibration device for a terminating matching resistor, including a calibration circuit for the terminating matching resistor as described in any one of the first aspects.

[0029] The aforementioned calibration circuit, method, and apparatus for terminating matching resistors include a calibration circuit comprising an AUX channel receiver, a first terminating resistor, a second terminating resistor, and a switch module. The first and second terminating resistors are connected in series between a first connection point and a second connection point. The switch module is electrically connected to the input terminal of the AUX channel receiver and is used to switch between a first operating state and a second operating state. This allows for flexible switching between different operating states without the need for a separately designed comparator circuit, simplifying the circuit structure and saving chip area. In the first operating state, the switch module configures the input terminal of the AUX channel receiver to connect to the first and second connection points to perform the AUX signal reception function, thus simplifying the overall structure of the calibration circuit without affecting the original AUX reception function. In the second operating state, the switch module configures the input terminal of the AUX channel receiver to connect to the common-mode node and the reference voltage terminal to perform the calibration function for the first and second terminating resistors. This allows for direct measurement and calibration of the actual first and second terminating resistors using external current and voltage sources. Because the calibration path fully incorporates both the first and second parasitic resistances, the calibration results more closely approximate the actual resistance values ​​during chip operation, thereby improving the accuracy of termination matching, better suppressing signal reflections, and ensuring signal integrity. Furthermore, in the second operating state, this application employs a two-step calibration process to independently and precisely calibrate the first termination resistor (corresponding to the pull-up resistor) and the second termination resistor (corresponding to the pull-down resistor). This ensures that the sum of the two resistors and the parasitic resistances along their respective paths is precisely equal to the target value (e.g., 50Ω), thus stabilizing the common-mode node voltage at the preset reference voltage value. This design guarantees the symmetry of the positive and negative paths of the differential signal, resulting in a deviation-free eye diagram in the Y-axis direction, better eye diagram quality, and more stable link transmission. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the circuit structure of an AUX channel differential pair in one embodiment;

[0032] Figure 2 This is a schematic diagram of a circuit structure used to directly measure the resistance value of an RTN resistor in one embodiment.

[0033] Figure 3 This is a schematic diagram of a self-calibration process using an internal RTN resistor in one embodiment;

[0034] Figure 4 This is a schematic diagram of the structure of a calibration circuit for a terminal matching resistor provided in one embodiment of this application;

[0035] Figure 5 A schematic diagram of the structure of a calibration circuit for a terminal matching resistor provided in another embodiment of this application;

[0036] Figure 6 A schematic diagram of the structure of a calibration circuit for a terminal matching resistor provided in another embodiment of this application;

[0037] Figure 7 This is a schematic flowchart illustrating a calibration method for a terminal matching resistor provided in one embodiment of this application. Detailed Implementation

[0038] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0040] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0041] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0042] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0043] When used herein, the singular forms of “a,” “an,” and “ / the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0044] To better understand the technical solutions in this application, a brief explanation of the technical terms and related technologies that may appear in this application will be provided first.

[0045] 1) Termination resistors (RTN resistors) play a crucial role in DisplayPort, primarily serving the high-speed differential signal channels (Main Link Lanes and AUX Channel). DisplayPort high-speed differential signal lines (such as D+ and D- of each lane) physically constitute transmission lines, specifically as follows: Figure 1 As shown. To ensure that the signal is not reflected at the end of the transmission line (the receiving end), the characteristic impedance of the transmission line (usually designed as a 100Ω differential impedance) must be terminated by a matching resistor at the receiving end. The RTN resistor is the terminating resistor connected in parallel between the differential signal pairs (D+ and D-), and its typical value is 100Ω.

[0046] It should be understood that precise 100Ω differential termination impedance matching can suppress signal reflections to the greatest extent, ensuring the integrity of high-speed signal transmission (clear signal waveforms and eye diagrams), ensuring that the DP link (main link and AUX channel) can be established stably and reliably and operate in a high-performance state, and providing the necessary DC path for the receiving circuit. It can be said that without properly designed and placed RTN resistors, DisplayPort cannot achieve its advertised high bandwidth and stability. It is one of the most fundamental and critical passive components in high-speed digital interface design.

[0047] 2) The AUX channel is an auxiliary channel, which is an independent bidirectional communication channel included in the DP interface.

[0048] In the DP interface, both the Main Link Lanes and AUX Channel use RTN resistors, so the circuit layout and range settings are usually the same. There are generally two existing methods for calibrating RTN resistors. The first is to directly measure the resistance value of the differential signal channel, such as... Figure 2 As shown. This method is simple to measure, but it cannot accurately calibrate the 50Ω resistance value, and the measuring instrument will introduce measurement errors, limiting its accuracy. The second method involves adding an RTN resistor self-calibration circuit inside the chip, as shown in the flowchart. Figure 3 As shown. This method is highly automated, but the measurement part is a replication module of the RTN resistor, and the calibration accuracy is relatively low.

[0049] To address the problems existing in related technologies, this application aims to provide a calibration circuit that reuses the AUX_RX circuit (i.e., the receiving circuit of the AUX channel) without affecting the RX function of the AUX, and eliminates the need for a separate calibration circuit, thus simplifying the calibration process and saving chip area by using a termination matching resistor. Compared to conventional methods, the results measured by the calibration circuit of this application include the parasitic resistance in the actual path, resulting in more accurate calibration results. Furthermore, this application can calibrate two 50Ω resistors separately, ensuring that the eye diagram has no deviation in the Y-axis direction, resulting in better eye diagram quality.

[0050] For example, Figure 4 This is a schematic diagram of the structure of a calibration circuit for a terminal matching resistor provided in one embodiment of this application, as shown below. Figure 4 As shown, the device may include: an AUX channel receiver 401, a first terminating resistor 402, a second terminating resistor 403, and a switch module 404. The first terminating resistor 402 and the second terminating resistor 403 are connected in series between a first connection point and a second connection point. The switch module 404 is electrically connected to the input terminal of the AUX channel receiver 401 and is used to switch between a first operating state and a second operating state. In the first operating state, the switch module 404 is used to configure the input terminal of the AUX channel receiver 401 to connect to the first connection point and the second connection point to perform the AUX signal reception function. In the second operating state, the switch module 403 is used to configure the input terminal of the AUX channel receiver 401 to connect to a common-mode node and a reference voltage terminal to perform the calibration function of the first terminating resistor 402 and the second terminating resistor 403.

[0051] Optionally, in this embodiment, the first terminating resistor 402 and the second terminating resistor 403 are both adjustable resistors, and their resistance values ​​can be adjusted by digital control words to achieve precise 100Ω differential terminating matching (i.e., the target value of each resistor is 50Ω).

[0052] For example, the receiver 401 of the AUX channel in this embodiment can be a high-precision differential receiver, whose core circuit is a comparator used to compare the voltage magnitudes of the two input terminals and output a digital level.

[0053] In the first operating state (normal operating mode), the switch module 404 is used to configure the input terminals of the AUX channel receiver 401 to connect to the first connection point and the second connection point. At this time, the two input terminals of the AUX channel receiver 401 receive differential signals from the first connection point (e.g., connected to the AUX_DP signal line) and the second connection point (e.g., connected to the AUX_DN signal line), respectively, and perform normal AUX signal reception functions for communication functions specified by the DisplayPort protocol, such as link training and reading display information.

[0054] In the second operating state (calibration mode), the switch module 404 configures the input of the AUX channel receiver 401 to connect to the common-mode node Vcm and the reference voltage Vref. Specifically, the first input of the AUX channel receiver 401 is connected to the common-mode node Vcm (i.e., the series connection point of the first terminating resistor 402 and the second terminating resistor 403), and the second input is connected to the internal high-precision reference voltage source Vref. At this time, the AUX channel receiver 401 is multiplexed as a calibration comparator to compare the voltage of the common-mode node Vcm with the reference voltage Vref, and its output signal indicates whether calibration is complete.

[0055] In this embodiment, by configuring the switch switching module 404, the receiver 401 of the AUX channel can be multiplexed as a comparator in calibration mode, eliminating the need to add a separate calibration comparator circuit, simplifying the circuit design and significantly saving chip area.

[0056] In this embodiment, the calibration process is performed directly on the first terminating resistor 402 and the second terminating resistor 403 that are actually in use, rather than replicating the resistors, so that the calibration results are closer to the actual working state of the chip.

[0057] Furthermore, this embodiment uses a two-step calibration process (detailed in subsequent embodiments) to independently calibrate the first terminating resistor 402 and the second terminating resistor 403, ensuring that the sum of the two resistors and their respective path parasitic resistances is exactly equal to 50Ω, thereby stabilizing the common-mode node Vcm voltage at a preset value, ensuring the symmetry of the positive and negative differential signals, and improving the eye diagram quality.

[0058] For example, in the first operating state, the calibration circuit further includes: an internal common-mode voltage amplifier, the output of which is connected to a common-mode node for providing a common-mode voltage to a first terminating resistor and a second terminating resistor; a first connection point connected to the positive terminal of an external AUX channel via a first parasitic resistance; a second connection point connected to the negative terminal of an external AUX channel via a second parasitic resistance; a first end of the first terminating resistor connected to a first input terminal of the receiver of the AUX channel and the first connection point, and a second end of the first terminating resistor connected to the common-mode node; a first end of the second terminating resistor connected to a second input terminal of the receiver of the AUX channel and the second connection point, and a second end connected to the common-mode node.

[0059] For example, in the second operating state, the calibration circuit further includes: an external current source and an external voltage source; the external current source is connected to a first connection point through a first parasitic resistor; the external voltage source is connected to a second connection point through a second parasitic resistor; a first end of a first terminating resistor is connected to the first connection point, and a second end of the first terminating resistor is connected to a common-mode node; a first end of a second terminating resistor is connected to the second connection point, and a second end of the second terminating resistor is connected to a common-mode node; a first input terminal of the receiver of the AUX channel is connected to the common-mode node, and a second input terminal of the receiver of the AUX channel is connected to a reference voltage terminal.

[0060] In the first operating state, the internal common-mode voltage amplifier and the common-mode node are connected; in the second operating state, the internal common-mode voltage amplifier and the common-mode node are disconnected.

[0061] In the second operating state, the receiver of the AUX channel is configured as a high-precision comparator, and the output signal of the receiver of the AUX channel is used to indicate the magnitude relationship between the common-mode node voltage and the reference voltage.

[0062] In the above embodiments, the receiver 401 of the AUX channel is multiplexed as a calibration comparator by the switch switching module 404, eliminating the need for an additional independent calibration circuit. The calibration path includes the first parasitic resistance and the second parasitic resistance, making the results closer to actual operating conditions. Furthermore, the above embodiments allow for separate calibration of the first terminating resistor 402 and the second terminating resistor 403 to ensure the accuracy of the common-mode node Vcm and guarantee the symmetry of the eye diagram along the Y-axis.

[0063] For example, Figure 5 A schematic diagram of the calibration circuit for the terminal matching resistor provided in another embodiment of this application is shown below. Figure 5As shown, in the first operating state, the first input terminal of the AUX channel receiver is connected to the first terminal of resistor RTN1 and the first terminal of AUX_DP, respectively. The second terminal of AUX_DP is connected to AUX_CH_P through resistor Rpara1. The second terminal of resistor RTN1 is connected to the output terminal of the internal common-mode voltage amplifier. The second input terminal of the AUX channel receiver is connected to the first terminal of resistor RTN2 and the first terminal of AUX_DN, respectively. The second terminal of AUX_DN is connected to AUX_CH_N through resistor Rpara2. The second terminal of resistor RTN2 is connected to the output terminal of the internal common-mode voltage amplifier, and the output terminal of the internal common-mode voltage amplifier forms the Vcm common-mode node. In the second operating state, the first input terminal of the AUX channel receiver is connected to the second terminal of resistor RTN1 and the second terminal of resistor RTN2, respectively. The first terminal of resistor RTN1 is connected to the first terminal of AUX_DP, and the second terminal of AUX_DP is connected to a current source through resistor Rpara1. The first terminal of resistor RTN2 is connected to the first terminal of AUX_DN, and the second terminal of AUX_DN is connected to a voltage source through resistor Rpara2. The second input terminal of the AUX channel receiver is connected to the reference voltage terminal Vref.

[0064] like Figure 5 As shown, for clarity, the two sets of ports are labeled A and B. In the first operating state, both inputs of the AUX channel receiver are connected to port A (AUX_DP and AUX_DN pads), and the pads of AUX_DP / DN are connected to port A (AUX_CH_P / AUX_CH_N channels). At this time, the switch at point C is closed, and the output of the internal common-mode voltage amplifier is connected to the Vcm common-mode node. Correspondingly, in the second operating state, both inputs of the AUX channel receiver are connected to port B (one end is the Vcm common-mode node, and the other end provides the internal reference voltage). The pads of AUX_DP / DN are connected to port B (I1 is the current source, and V2 is the voltage source). At this time, the switch at point C is open, so the Vcm common-mode node has no internal power supply.

[0065] For example, Figure 6 This is a schematic diagram of the calibration circuit for the terminal matching resistor provided in another embodiment of this application. Figure 6 This describes the circuit structure in its second operating state after the switching process. (Combined with...) Figure 5 , Figure 6As can be seen, in the second operating state, the calibration circuit also includes: an external current source I1, an external voltage source V2, a first parasitic resistor Rpara1, and a second parasitic resistor Rpara2. The external current source I1 is connected to the first connection point via the first parasitic resistor Rpara1. The first parasitic resistor Rpara1 represents the parasitic resistance of the trace from the first connection point (e.g., the AUX_DP pad) to the on-chip first terminating resistor RTN1. The external voltage source V2 is connected to the second connection point via the second parasitic resistor Rpara2. The second parasitic resistor Rpara2 represents the parasitic resistance of the trace from the second connection point (e.g., the AUX_DN pad) to the on-chip second terminating resistor RTN2. The first terminating resistor RTN1 has its first end connected to the first connection point and its second end connected to the common-mode node Vcm. The second terminating resistor RTN2 has its first end connected to the second connection point and its second end connected to the common-mode node Vcm. The first input (e.g., non-inverting input) of the receiver for the AUX channel is connected to the common-mode node Vcm, and the second input (e.g., inverting input) of the receiver for the AUX channel is connected to the internal reference voltage source Vref.

[0066] In this embodiment, in the second operating state, the connection between the internal common-mode voltage amplifier and the common-mode node Vcm is disconnected to avoid interference with the calibration process.

[0067] In this embodiment, the circuit structure described above ensures that the calibration path fully includes the first parasitic resistance Rpara1 and the second parasitic resistance Rpara2, enabling the calibration results to compensate for the influence of the actual trace parasitic resistance and further improve the matching accuracy.

[0068] For example, in the second operating state, the voltage of the common-mode node is changed by successively adjusting the resistance value of the second terminating resistor. Figure 6 Taking the circuit structure shown as an example, assume that the RTN calibration circuit has been completed. I1 is an external current source with a current of I and a voltage of V1; V2 is an external voltage source with a voltage of V2; Rpara1 and Rpara2 are parasitic resistances on the AUX_DP / AUX_DN channels; RTN1 and RTN2 are on-chip adjustable termination resistors; Vref is a known internal reference voltage; Vcm is the voltage divider node of the termination resistors; the receiver of the Aux channel is designed as a high-precision comparator to meet the RTN resistor accuracy requirements in the DP protocol. The RTN resistor calibration process and derivation formulas are given below:

[0069] First, adjust the RTN2 resistor trim setting from low to high until the OUT signal flips. Record and set the current trim setting to complete the RTN2 resistor calibration.

[0070] In this embodiment, when the output of the receiver in the AUX channel flips, the voltage of the common-mode node is determined to be equal to the voltage of the internal reference voltage source, and the calibration value of the second terminating resistor is locked. Since the comparator has high precision, the output signal flip indicates that the voltage values ​​Vcm and Vref are sufficiently close; therefore, Vcm = Vref can be considered to be true at this point. The derivation formula is as follows:

[0071]

[0072]

[0073] Specifically, first, the external voltage source V2 is set to a known voltage value (e.g., 0V), and the external current source I1 is set to a precise current value I. At this point, the voltage at the common-mode node Vcm is determined by the branch containing the second terminating resistor 403. ,in, Rpara2 is the current resistance value of the second terminating resistor, and Rpara2 is the second parasitic resistance. Then, the digital control word of the second terminating resistor is adjusted sequentially from low to high to change its resistance value. Simultaneously, the output signal OUT of the AUX channel receiver is monitored. When the output signal OUT flips (e.g., changes from low to high), it indicates that the voltage of the common-mode node Vcm is equal to the voltage of the internal reference voltage source Vref, i.e., Vcm = Vref. At this time, according to the formula... Calculate and lock the calibration value of the second terminating resistor. This is done by setting... The specific values ​​of Vref and I (e.g., Vref = 0.5V, V2 = 0V, I = 10mA) can make This completes the accurate calibration of the second terminating resistor, and the calibration result includes the second parasitic resistance Rpara2.

[0074] Furthermore, the voltage at the first connection point can be changed by successively adjusting the resistance value of the first terminating resistor; if the voltage at the first connection point meets the preset conditions, the calibration value of the first terminating resistor can be locked.

[0075] In this embodiment, the RTN1 resistor trim setting is adjusted from low to high until it reaches the voltage displayed by the I1 current source. Record and set the current trim level to complete the RTN1 resistor calibration.

[0076] RTN1 satisfies the following constraints:

[0077]

[0078] Specifically, after completing the first calibration step, the calibration setting of the second terminating resistor remains unchanged, as do the external current source I and the external voltage source V2. At this time, the voltage V1 at the first connection point is determined by the branch containing the first terminating resistor. , Let be the resistance value of the first terminating resistor. This is the first parasitic resistance. Since the first calibration step has been completed, the common-mode node Vcm has been precisely locked at... ,therefore, Then, the digital control word of the first terminating resistor is adjusted sequentially from low to high to change its resistance value. Simultaneously, the voltage V1 at the first connection point (i.e., the displayed voltage at the external current source I1) is monitored. When voltage V1 meets the... The current range of the first terminating resistor is locked as the calibration value. At this point, the formula can be used... Determine the calibration results and complete the precise calibration of the first terminating resistor 402. The calibration results include the first parasitic resistance Rpara1.

[0079] In this embodiment, the internal RTN resistor self-calibration circuit is simplified by reusing the comparator in the AUX_RX circuit, saving circuit area. Since the RTN resistor is the resistor used in the actual circuit, the measurement result includes parasitic resistance in the actual path, eliminating the influence of trace parasitic resistance on matching accuracy and making the calibration result more accurate. Furthermore, the calibration circuit of this application can also separately calibrate the two 50Ω resistors between VCM and AUX_DP / AUX_DN, ensuring that the common-mode node Vcm voltage is exactly equal to Vref, guaranteeing symmetry between the positive and negative differential signals, resulting in no deviation in the eye diagram in the Y-axis direction and better eye diagram quality. This application requires only two adjustments and two judgments to complete the entire calibration, without complex algorithms or additional test points. It also cleverly separates the two operating states, ensuring that the calibration mode does not affect the AUX signal reception function in normal operating mode.

[0080] For example, such as Figure 7 As shown, this application also provides a calibration method for a terminating matching resistor, which can be used to perform at least one of the following steps using the calibration circuit of the terminating matching resistor described above:

[0081] In step S701, the calibration circuit is configured to the first working state by switching the module to perform the AUX signal receiving function.

[0082] In step S702, the calibration circuit is configured to the second working state through the switch switching module to perform the calibration function for the first terminating resistor and the second terminating resistor.

[0083] In this embodiment, by using a switching module, the receiver of the AUX channel, originally used for receiving AUX signals, is multiplexed as a calibration comparator in the second operating state, eliminating the need for a separate comparator circuit. This design simplifies the calibration circuit structure and significantly saves chip area without affecting the original AUX receiving function.

[0084] Furthermore, this application also provides a calibration device for a terminating resistor, including the aforementioned calibration circuit for the terminating resistor. The calibration circuit includes: an AUX channel receiver, a first terminating resistor, a second terminating resistor, and a switch module. The calibration circuit has a first operating state and a second operating state, used to perform AUX signal reception and terminating resistor calibration functions, respectively.

[0085] In this embodiment, the calibration circuit can be integrated into a display interface control chip to provide accurate terminal matching for DisplayPort.

[0086] Optionally, the calibration device for the aforementioned terminal matching resistor may further include: a control unit electrically connected to the calibration circuit, used to control the switching of the operating state of the calibration circuit and the execution of the calibration process. Specifically, the control unit is used to perform at least one of the following operations:

[0087] Send a control signal to the switching module of the calibration circuit to switch it between the first and second operating states;

[0088] In the second working state, an adjustment signal is sent to the calibration circuit to adjust the resistance values ​​of the first terminating resistor and / or the second terminating resistor one by one.

[0089] The comparison result signal output by the receiver of the AUX channel in the calibration circuit is received, and the calibration is determined based on the comparison result signal.

[0090] Upon completion of calibration, the calibrated terminal resistance level information is stored in the storage unit.

[0091] It should be understood that the control unit can be a microcontroller (MCU), digital signal processor (DSP), field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), or other programmable logic device. The storage unit is electrically connected to the control unit and is used to store calibration data and configuration information. Specifically, the storage unit is used to store at least one of the following information:

[0092] The calibration range value of the first terminating resistor;

[0093] The calibration range value of the second terminating resistor;

[0094] The reference voltage and current values ​​used during the calibration process;

[0095] Device identification information and configuration parameters.

[0096] The storage unit may include at least one of non-volatile memory (such as EEPROM, Flash) and volatile memory (such as SRAM, DRAM).

[0097] For example, the calibration device for the terminal matching resistor described above may further include: a communication interface electrically connected to the control unit for data communication with external devices. Specifically, the communication interface is used to perform at least one of the following operations:

[0098] Receive calibration start command from external device (such as host processor);

[0099] Send calibration completion status and calibration results to external devices;

[0100] In the first operating state, it transmits the link training data and display information received by the AUX channel.

[0101] The communication interface may include at least one of the following: I2C interface, SPI interface, UART interface, or other standard communication interface.

[0102] The calibration device for the terminating matching resistor in this embodiment includes the aforementioned calibration circuit, and therefore inherits all the beneficial effects of the calibration circuit. Furthermore, this embodiment also has the following beneficial effects:

[0103] The control unit automatically executes a two-step calibration process without manual intervention, improving production testing efficiency. The calibrated terminal resistance values ​​are saved in the storage unit, allowing for direct use upon each power-on without recalibration. Interaction with external devices via a communication interface supports remote calibration initiation and calibration status reporting, facilitating system integration. Furthermore, calibration is completed automatically or upon command after power-on, ensuring terminal matching accuracy and improving signal integrity of the display interface.

[0104] It should be understood that the calibration device for the terminal matching resistor in this embodiment can be widely used in the following scenarios:

[0105] Display interface control chip: Integrated into the DisplayPort control chip of computer graphics cards, monitors, TVs, projectors and other devices to ensure the stability of high-speed video transmission.

[0106] Signal repeater / retimer: Used in DisplayPort signal repeater or retimer devices to ensure that the signal still has good eye diagram quality after long-distance transmission.

[0107] Test and measurement equipment: Integrated into DisplayPort protocol analyzers, signal generators, or conformance test equipment, used for accurate measurement and calibration of the end-matching characteristics of the device under test.

[0108] Consumer electronics: Applied to USB Type-C interface devices with DisplayPort AltMode functionality, such as smartphones, tablets, and laptops, to ensure video output quality.

[0109] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0111] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A calibration circuit for a terminating matching resistor, characterized in that, This device is used in a display interface and includes: a receiver for an AUX channel, a first terminating resistor, a second terminating resistor, and a switch module. The first terminating resistor and the second terminating resistor are connected in series between a first connection point and a second connection point. The switch module is electrically connected to the input terminal of the receiver for the AUX channel and is used to switch between a first operating state and a second operating state. In the first working state, the switch switching module is used to configure the input terminal of the receiver of the AUX channel to be connected to the first connection point and the second connection point, so as to perform the AUX signal receiving function; In the second operating state, the switch switching module is used to configure the input terminal of the receiver of the AUX channel to be connected to the common mode node and the reference voltage terminal to perform the calibration function of the first terminating resistor and the second terminating resistor.

2. The calibration circuit for the terminal matching resistor according to claim 1, characterized in that, In the second operating state, the calibration circuit further includes: an external current source and an external voltage source; The external current source is connected to the first connection point through a first parasitic resistor; The external voltage source is connected to the second connection point through a second parasitic resistor; The first end of the first terminating resistor is connected to the first connection point, and the second end of the first terminating resistor is connected to the common-mode node. The first end of the second terminating resistor is connected to the second connection point, and the second end of the second terminating resistor is connected to the common-mode node; The first input terminal of the receiver of the AUX channel is connected to the common-mode node, and the second input terminal of the receiver of the AUX channel is connected to the reference voltage terminal.

3. The calibration circuit for the terminal matching resistor according to claim 1, characterized in that, In the first operating state, the calibration circuit further includes: an internal common-mode voltage amplifier, the output of which is connected to the common-mode node, for providing a common-mode voltage to the first terminating resistor and the second terminating resistor; The first connection point is connected to the positive terminal of the external AUX channel via a first parasitic resistor; The second connection point is connected to the negative terminal of the external AUX channel via a second parasitic resistor; The first end of the first terminating resistor is connected to the first input terminal of the receiver of the AUX channel and the first connection point, and the second end of the first terminating resistor is connected to the common mode node; The first end of the second terminating resistor is connected to the second input terminal of the receiver of the AUX channel and the second connection point, and the second end is connected to the common mode node.

4. The calibration circuit for the terminal matching resistor according to claim 3, characterized in that, In the first operating state, the internal common-mode voltage amplifier and the common-mode node are connected; in the second operating state, the internal common-mode voltage amplifier and the common-mode node are disconnected.

5. The calibration circuit for the terminal matching resistor according to claim 1, characterized in that, In the second operating state, the voltage of the common-mode node is changed by successively adjusting the resistance value of the second terminating resistor.

6. The calibration circuit for the terminal matching resistor according to claim 5, characterized in that, In the event that the output of the receiver in the AUX channel flips, the voltage of the common-mode node is determined to be equal to the voltage of the internal reference voltage source, and the calibration value of the second terminating resistor is locked.

7. The calibration circuit for the terminal matching resistor according to claim 5, characterized in that, By successively adjusting the resistance value of the first terminal resistor, the voltage at the first connection point is changed; If the voltage at the first connection point meets the preset conditions, the calibration value of the first terminating resistor is locked.

8. The calibration circuit for the terminating matching resistor according to any one of claims 1 to 7, characterized in that, The receiver of the AUX channel is configured as a high-precision comparator in the second operating state, and the output signal of the receiver of the AUX channel is used to indicate the magnitude relationship between the common-mode node voltage and the reference voltage.

9. A calibration method for a terminating matching resistor, characterized in that, The calibration circuit using the terminating matching resistor according to any one of claims 1 to 8 performs at least one of the following steps: The calibration circuit is configured to the first working state by the switch switching module to perform the AUX signal receiving function; The calibration circuit is configured to the second operating state by means of the switch switching module, and the calibration function of the first terminating resistor and the second terminating resistor is performed.

10. A calibration device for a terminating matching resistor, comprising the calibration circuit for the terminating matching resistor as described in any one of claims 1 to 8.

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