A high-speed SERDES high-precision resistance calibration module circuit

Abstract

This invention provides a SerDes resistor calibration circuit for impedance matching calibration based on a calibration driver. The calibration driver is copied from the driver of the SerDes transmitter, and its port includes terminating resistors and other modules. The resistor calibration circuit includes a calibration control module, an equivalent internal resistance array of the calibration driver, an off-chip reference resistor, a comparator, a current generation module, and a compensation module. The compensation module is constructed using layout routing, and its layout routing is identical to that of the other modules. It is used to compensate for errors caused by the internal resistance of other modules in the resistor calibration circuit. By introducing the compensation module, the resistor calibration circuit provided by this invention compensates for the calibration errors caused by the internal resistance of other modules at the port, significantly improving the accuracy of the calibration results and enhancing the accuracy and reliability of data transmission.

Description

Technical Field

[0001] This invention relates to the field of data transmission, and more particularly to a high-precision resistor calibration circuit for high-speed serial interfaces. Background Technology

[0002] In recent years, with the development of technology in the electronics industry, the data transmission speed of traditional parallel interfaces has reached a bottleneck, and they have been replaced by faster serial interfaces. Today's high-speed serial interfaces mainly use serializer / deserializer technology combined with differential signal transmission technology, which features low power consumption, strong anti-interference, and high speed. Currently, the highest transmission rate of commercial serial interfaces can generally reach more than 10Gbps.

[0003] Among them, the serializer / deserializer (SerDes) is a technology that converts parallel data into a high-speed serial data stream and restores the high-speed serial data stream back to parallel data. It is one of the core technologies for high-speed serial interface data transmission. Differential signal transmission technology is an electronic technology that transmits signals through two complementary wires. Its core principle is to determine the signal state by detecting the voltage difference between the two wires. It is also one of the core technologies for high-speed data transmission. Currently, differential signal transmission technology mainly includes standards such as low-voltage differential signaling and current-mode logic (CML), which are widely used in high-speed serial interfaces.

[0004] Impedance matching calibration is crucial for the proper functioning of SerDes drivers. It involves dynamically adjusting the value of the on-chip termination resistor to precisely match the characteristic impedance of the transmission line. Impedance matching calibration reduces signal reflection, distortion, and interference, ensuring signal integrity, reducing the bit error rate during transmission, and improving the stability and reliability of data transmission. Calibration is applicable to different transmission media and environments, allowing the termination resistor value to adaptively adjust according to the specific medium and environment, ensuring efficient data transmission under various conditions. Failure to perform calibration can lead to signal ringing, soaring bit error rates, decreased power transmission efficiency, and increased common-mode noise.

[0005] Impedance matching calibration is achieved through a resistor calibration circuit. The conventional method for constructing a resistor calibration circuit is to copy the driver from the SerDes transmitter to the local resistor calibration module, called the calibration driver, and then perform impedance matching calibration based on the calibration driver. A typical existing resistor calibration circuit is as follows: Figure 1As shown in the diagram. The equivalent internal resistance array of the calibration driver simulates the termination resistors in the calibration driver, and its resistance can be changed according to the control code sent by the calibration control module. The calibration control module controls the entire calibration process according to its internal calibration control logic. The external reference resistor provides a high-precision reference for resistor calibration. The precision constant current source provides a stable reference current for the reference resistor, the equivalent internal resistance array of the calibration driver, and the comparator. Comp is the comparator, which compares the voltage generated by the external reference resistor with the voltage generated by the equivalent internal resistance array of the calibration driver and feeds the comparison result back to the calibration control module. vddio represents the power supply pin. When the calibration circuit is working, the calibration control module sends a control code to the equivalent internal resistance array of the calibration driver according to the comparator output and the preset calibration control logic, and adjusts its resistance value. When the preset calibration control logic determines that the resistance of the equivalent internal resistance array of the calibration driver reaches the expected value (i.e., equal to the characteristic impedance of the transmission line) according to the comparator output, the calibration control module will output the control code at this time as the correct control code cali code to the terminating resistor at the transmitting end, the terminating resistor at the receiving end, or other modules that need to be calibrated, such as the phase-locked loop, for their use, so that the terminating resistor value of these modules is consistent with the characteristic impedance of the transmission line.

[0006] However, when the calibration results of the above calibration circuit are actually applied, there is still a large deviation between the driver impedance and the characteristic impedance of the transmission line, which leads to signal distortion and interference, increases the bit error rate and reduces the accuracy of data transmission. Summary of the Invention

[0007] To address the aforementioned problems and improve resistor calibration accuracy, this invention provides a resistor calibration circuit for a SerDes driver. This circuit performs impedance matching calibration based on a calibration driver, which is copied from the driver at the SerDes transmitter. The calibration driver includes a terminating resistor and other modules. The resistor calibration circuit calibrates the resistance value of the terminating resistor to match the port impedance of the calibration driver with the characteristic impedance of the transmission line. The resistor calibration circuit includes a calibration control module, an equivalent internal resistance array of the calibration driver, a current generation module, an external reference resistor, a comparator, and a compensation module.

[0008] The comparator is used to compare the voltage generated by the off-chip reference resistor with the voltage generated by the compensation module and the equivalent internal resistance array of the calibration driver, and output the comparison result to the calibration control module.

[0009] The calibration control module is used to send control codes to the equivalent internal resistance array of the calibration driver according to the output of the comparator and the preset calibration control logic to adjust its equivalent resistance value; or to output the correct control code to the target module according to the output of the comparator and the preset calibration control logic; the correct control code is used to adjust the resistance value of the target module termination resistor so that the resistance value of the target module termination resistor matches the characteristic impedance of the transmission line.

[0010] The compensation module is constructed by layout winding and is connected to the equivalent internal resistance array of the calibration driver;

[0011] The layout routing of the compensation module is the same as that of the other modules;

[0012] The current generation module is used to provide a stable reference current for the equivalent internal resistance array of the off-chip reference resistor and the calibration driver, thereby generating the voltage of the input comparator.

[0013] In some embodiments, the other module is an inductor module.

[0014] In some embodiments, the compensation module is constructed by winding around a layout metal layer.

[0015] In some embodiments, the target module specifically includes: a Serdes transmitter, a Serdes receiver, and a phase-locked loop module.

[0016] The resistor calibration circuit provided by this invention compensates for calibration errors caused by the internal resistance of other modules at the port by introducing a compensation module. This invention replicates the internal resistance of other modules into the compensation module using the same layout wiring, thereby achieving precise compensation and significantly improving the accuracy of the calibration results. Furthermore, the layout wiring eliminates the need for additional components, resulting in lower costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a resistor calibration circuit in the prior art;

[0019] Figure 2 This is a schematic diagram of the structure of a CML driver transmitter in the prior art;

[0020] Figure 3 A schematic diagram of a resistance calibration circuit provided by the present invention;

[0021] Figure 4 This invention illustrates a specific implementation of a compensation module layout routing method provided by the present invention; Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings.

[0023] To address the insufficient calibration accuracy of existing calibration circuits, it is necessary to identify the largest source of error in the existing circuits and make corresponding adjustments to improve calibration accuracy. The applicant has identified the following largest sources of error in the existing calibration circuits:

[0024] A schematic diagram of the existing CML driver transmitter is shown below. Figure 2 As shown, TXP represents the forward transmitting end of the differential signal pair, and R... TERMT This indicates a terminating resistor. In addition, the terminating resistor R... TERMT The end is also connected to an inductor module (tcoil). Existing high-speed SerDes drivers introduce additional functional modules at the port to improve transmitter performance, such as the inductor module (tcoil) for expanding bandwidth and suppressing reflections. Figure 2 As shown in the right figure, tcoil is essentially an on-chip integrated inductor network with an internal resistance of 5 to 7 ohms. While tcoil is introduced in high-speed SerDes drivers, existing calibration circuits do not etch the internal resistance of tcoil into the calibration circuit itself. This results in a 5 to 7 ohm error between the resistance value obtained by the calibration circuit and the actual required termination resistance, significantly reducing the accuracy of the calibration results.

[0025] To compensate for the error caused by the internal resistance of other modules (such as the inductor module tcoil) located at the SerDes driver port due to resistance calibration, and to improve the accuracy of the resistance calibration circuit, this invention provides, for example... Figure 3 The resistor calibration circuit shown.

[0026] Compared with existing resistance calibration circuits ( Figure 1 Compared to the present invention, the resistance calibration circuit provided by the present invention ( Figure 3 A compensation module is introduced to compensate for errors caused by the internal resistance of the tcoil. To achieve high-precision calibration, the circuitry at the driver's transmitting end needs to be completely replicated into the resistor calibration circuit. The equivalent internal resistance array of the calibration driver corresponds to the termination resistor of the calibration driver, and the compensation module corresponds to the inductor module tcoil of the calibration driver. According to... Figure 2 The diagram shows the driver transmitter circuit. The inductor module tcoil is connected to the terminating resistor R. TERMTTherefore, in the resistor calibration circuit, the compensation module is connected to the end of the equivalent internal resistance array of the calibration driver, and the layout traces of the compensation module are the same as those of the inductor module. Consequently, the resistance of the compensation module will also be consistent with the internal resistance of the inductor module tcoil. In this way, the transmitting circuit is completely copied into the resistor calibration circuit, avoiding the error caused by the internal resistance of tcoil for resistor calibration.

[0027] In the resistor calibration circuit provided by this invention, the compensation module and the equivalent internal resistance array of the calibration driver jointly simulate the transmitting circuit of the driver. The two input terminals of the comparator should be connected to the external reference resistor and the component formed by the compensation module and the equivalent internal resistance array of the calibration driver, respectively, to compare the voltage generated by the external reference resistor and the voltage generated by the transmitting circuit simulated by the compensation module and the equivalent internal resistance array of the calibration driver.

[0028] The compensation module is constructed by layout routing, and the layout routing of the compensation module is the same as that of the inductor module.

[0029] When constructing a compensation module using layout routing, the overall resistance of the metal lines used to construct the compensation module must be equal to the internal resistance of the tcoil module to compensate for tcoil internal resistance errors. This can be achieved by completely replicating the layout traces of the inductor module into the compensation module, making their layout traces identical. Specifically, during the layout design phase of the SerDes driver, the layout traces of the tcoil module need to be designed first, and then the layout traces of the tcoil module need to be replicated to the corresponding position of the compensation module in the resistance calibration circuit, and connected to the equivalent internal resistance array of the calibration driver.

[0030] Figure 4 The document provides a specific layout implementation of the compensation module, where the red box shows the top-level (AP layer) layout of the resistor correction circuit. Figure 4 The highlighted traces in the diagram represent the specific layout implementation of the compensation module on the metal7 layer (M7 layer).

[0031] Table 1 compares the calibration results of the resistor calibration circuit provided by this invention with the results of manual calibration. The manual calibration results can be considered as accurate values. As can be seen from Table 1, the calibration results obtained using the resistor calibration circuit provided by this invention are very close to the accurate results obtained by manual calibration, indicating that the calibration accuracy of the termination resistor calibration circuit provided by this invention is extremely high.

[0032] Table 1 Comparison of calibration results

[0033]

[0034] This invention compensates for the errors introduced by the tcoil during the replication of the SerDes driver in the resistor calibration circuit by constructing a compensation module, thereby improving the accuracy and reliability of data transmission. This invention uses a layout-based wire-wrapping method to construct the compensation module. By using the same layout wire-wrapping, the tcoil traces are completely replicated into the compensation module of the calibration circuit, thus achieving precise compensation and significantly improving the accuracy of the calibration results. Furthermore, the layout-based wire-wrapping method eliminates the need for additional components, resulting in lower costs and achieving a significant improvement in calibration accuracy without requiring large-scale modifications to existing resistor calibration circuits. The resistor calibration circuit for high-speed SerDes provided by this invention can significantly improve calibration accuracy, thereby improving the accuracy and reliability of high-speed serial interface data transmission, reducing signal distortion reflection and interference, and reducing the bit error rate.

[0035] In the description of the embodiments of this application, the words "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the words "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a specific manner.

[0036] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. Furthermore, unless otherwise stated, the term "multiple" means two or more.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. The terms "comprising," "including," "having," and their variations all mean "including but not limited to," unless otherwise specifically emphasized.

[0038] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. A SerDes resistance calibration circuit, which is used for impedance matching calibration according to a calibration driver, the calibration driver is copied from a driver of a Serdes sending end, the calibration driver includes a terminating resistance and other modules, the resistance calibration circuit is used for calibrating the resistance value of the terminating resistance, so that the calibration driver port impedance is matched with the transmission line characteristic impedance, characterized in that, The resistor calibration circuit includes a calibration control module, an equivalent internal resistance array of a calibration driver, a current generation module, an external reference resistor, a comparator, and a compensation module. ​ The comparator is used to compare the voltage generated by the off-chip reference resistor with the voltage generated by the compensation module and the equivalent internal resistance array of the calibration driver, and output the comparison result to the calibration control module. The calibration control module is used to send control codes to the equivalent internal resistance array of the calibration driver according to the output of the comparator and the preset calibration control logic to adjust its equivalent resistance value; or to output the correct control code to the target module according to the output of the comparator and the preset calibration control logic; the correct control code is used to adjust the resistance value of the termination resistor of the target module to match the characteristic impedance of the transmission line. The compensation module is constructed by layout winding and is connected to the equivalent internal resistance array of the calibration driver; The layout routing of the compensation module is the same as that of the other modules; The current generation module is used to provide a stable reference current for the equivalent internal resistance array of the off-chip reference resistor and the calibration driver, thereby generating the voltage of the input comparator.

2. The resistance calibration circuit according to claim 1, characterized in that, The other modules are inductor modules.

3. The resistance calibration circuit according to claim 1, characterized in that, The compensation module is constructed by winding wires around the metal layer of the layout.

4. The resistance calibration circuit according to claim 1, characterized in that, The target module specifically includes: a Serdes transmitter, a Serdes receiver, and a phase-locked loop module.

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