Receiver circuit and chip

Abstract

The invention discloses a receiver circuit and a chip, the receiver circuit comprises a resistance voltage divider and a comparator, the positive input end of the comparator is connected with the output end of a first resistor of the resistance voltage divider, the negative input end of the comparator is connected with the output end of a third resistor of the resistance voltage divider, and the receiver circuit further comprises a negative feedback amplifier, the positive input end of the negative feedback amplifier is connected with a fixed reference voltage, the negative input end of the negative feedback amplifier is connected with the output end of the first resistor and the output end of the third resistor, and the output end of the negative feedback amplifier is connected with a reference node of the resistance voltage divider; the negative feedback amplifier is configured to dynamically adjust the output voltage of the negative feedback amplifier according to the output voltage of the output ends of the first resistor and / or the third resistor and a negative feedback mechanism. According to the receiver chip, the receiver circuit can cope with larger or smaller input common-mode voltage, and the problem that the input common-mode voltage range of an existing receiver chip is narrow is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a receiver circuit and a chip. Background Art

[0002] RS-485 and RS-422 are commonly used communication interface standards with the following features: maximum transmission rate of up to 10Mbps, maximum transmission distance of up to 4000 feet, and support for multi-point reception and transmission and bidirectional communication. However, the input common-mode voltage range of the current receiver is usually -7V to +12V, and the threshold range of signal detection is -200mV to +200mV.

[0003] In the prior art, when multiple devices are connected to the bus, the signal is transmitted through a long twisted pair. Due to noise interference in the actual environment, a large common-mode voltage offset may occur on the bus, causing the receiver input voltage to exceed its normal operating range (-7V to +12V). This situation will cause the receiver to be unable to correctly interpret the signal, thereby affecting the reliability of communication and system performance.

[0004] Based on this, a new technical solution is needed. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a receiver circuit and a chip to at least solve the problem of narrow input common mode voltage range of the existing receiver chip.

[0006] The embodiment of the present invention provides the following technical solutions: An embodiment of the present invention provides a receiver circuit, including a resistor divider and a comparator, wherein the resistor divider includes a first resistor, a second resistor, a third resistor and a fourth resistor, wherein an overall input terminal of the first resistor and the second resistor connected in series is connected to a first input common mode voltage, an overall input terminal of the third resistor and the fourth resistor connected in series is connected to a second input common mode voltage, an overall output terminal of the first resistor and the second resistor connected in series and an overall output terminal of the third resistor and the fourth resistor connected in series are connected to each other to form a reference node of the resistor divider, a positive input terminal of the comparator is connected to the output terminal of the first resistor, and a negative input terminal is connected to the output terminal of the third resistor, The receiver circuit further comprises a negative feedback amplifier, wherein a positive input terminal of the negative feedback amplifier is connected to a fixed reference voltage, a negative input terminal of the negative feedback amplifier is connected to an output terminal of the first resistor and an output terminal of the third resistor, and an output terminal of the negative feedback amplifier is connected to a reference node of the resistor divider; The negative feedback amplifier is configured to dynamically adjust the output voltage of the negative feedback amplifier according to the output voltage of the output terminal of the first resistor and / or the third resistor and a negative feedback mechanism.

[0007] Furthermore, the receiver circuit also includes an adjustable current source, a positive electrode of the adjustable current source is connected to the output end of the third resistor, and a negative electrode of the current source is grounded.

[0008] Furthermore, the receiver circuit further includes an electronic fuse, and the electronic fuse is used to control the adjustable current source.

[0009] Furthermore, the input voltage of the comparator ranges from ground voltage to power supply voltage.

[0010] Furthermore, the negative feedback amplifier dynamically adjusts the output voltage of the negative feedback amplifier according to a comparison result between the output voltage of the output end of the first resistor or the third resistor and the fixed reference voltage.

[0011] Further, when the negative feedback amplifier determines, according to the comparison result, that the first input common-mode voltage and / or the second input common-mode voltage is larger, the output voltage of the negative feedback amplifier is dynamically reduced; When the negative feedback amplifier determines, based on the comparison result, that the first input common-mode voltage and / or the second input common-mode voltage is smaller, the output voltage of the negative feedback amplifier is dynamically increased.

[0012] Furthermore, the output voltages of the first resistor and the third resistor, and the output voltage of the negative feedback amplifier are all continuously changing voltages.

[0013] Furthermore, the range of the first input common mode voltage and the second input common mode voltage is ±40V.

[0014] Furthermore, the receiver circuit is applied to an RS-485 interface chip.

[0015] The present invention also provides a chip, comprising any receiver circuit as described above.

[0016] Compared with the prior art, the at least one technical solution adopted in the embodiment of the present invention can achieve the following beneficial effects: A receiver circuit of the present invention adds a negative feedback amplifier to a resistor voltage divider, connects the positive input of the negative feedback amplifier to a fixed reference voltage, and connects the negative input to the output voltage after voltage division between a first resistor and a third resistor. The output of the negative feedback amplifier can dynamically adjust its output voltage according to the output voltage after voltage division between the first resistor and the second resistor, so that the output voltage after voltage division between the first resistor and the third resistor is within the input voltage range of the comparator, thereby enabling the receiver circuit to cope with larger or smaller input common-mode voltages, thereby solving the problem of narrow input common-mode voltage range of existing receiver chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a schematic diagram of an existing receiver circuit; Figure 2 is the existing receiver port voltage variation curve; Figure 3 is a schematic diagram of a receiver circuit of the present invention; Figure 4 This is the voltage variation curve of the receiver circuit port of the present invention.

[0019] The accompanying drawings of the present invention are as follows: 1. First resistor; 2. Second resistor; 3. Third resistor; 4. Fourth resistor; 5. Comparator; 6. Negative feedback amplifier; 7. Adjustable current source. DETAILED DESCRIPTION

[0020] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0021] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0022] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0023] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0024] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.

[0025] like Figure 1 As shown, the existing receiver circuit includes a group of resistor dividers and a comparator. The resistor divider converts the input voltage of -7V to +12V into a lower voltage, generally between 0V and 3.3V, or between 0V and 5V. The reference level of the resistor divider is a fixed potential, generally half of the power supply voltage. The comparator works under the power supply voltage. When the input voltage A / B is too large or too small, exceeding the range of -7V to +12V, so that the voltage Va / Vb after voltage division is less than 0V or greater than 3.3V, the comparator cannot compare the size of the input voltage and generates an erroneous output.

[0026] In addition, due to deviations and fluctuations in the chip manufacturing process, the resistance of the voltage divider resistor will produce random mismatches, and there will be an input mismatch voltage at the comparator input. Therefore, there is an error in the threshold of the comparator, and this error becomes larger and larger as the input voltage A / B range increases.

[0027] Based on this, this specification embodiment proposes a processing solution: Figure 3As shown, a receiver circuit of the present invention adds an amplifier circuit on the basis of the existing receiver circuit, the positive input end of the amplifier is the reference level, the negative input end is the voltage Va / Vb after the resistor voltage division, and the output can generate a variable reference level according to the size of the Va / Vb voltage and provide it to the resistor voltage division circuit, so that the voltage Va / Vb after the voltage division is within the range of the ground voltage to the power supply voltage. After adding the amplifier circuit, the present invention can work within a wider input common mode voltage range.

[0028] In addition, the present invention adds an adjustable current bias at the negative input end of the comparator 5, and the current is controlled by efuse, which can be calibrated after the chip is produced so that the receiver threshold of each chip is between -200mV and -50mV under PVT (process, voltage, temperature) conditions.

[0029] The technical solutions provided by various embodiments of the present application are described below in conjunction with the accompanying drawings.

[0030] like Figure 3~4 As shown, a receiver circuit provided by the present invention includes a resistor divider and a comparator 5, the resistor divider includes a first resistor 1, a second resistor 2, a third resistor 3 and a fourth resistor 4, the overall input end of the first resistor 1 and the second resistor 2 connected in series is connected to the first input common mode voltage, the overall input end of the third resistor 3 and the fourth resistor 4 connected in series is connected to the second input common mode voltage, the overall output end of the first resistor 1 and the second resistor 2 connected in series and the overall output end of the third resistor 3 and the fourth resistor 4 connected in series are connected to each other to form a reference node of the resistor divider, the positive input end of the comparator 5 is connected to the output end of the first resistor 1, and the negative input end is connected to the output end of the third resistor 3.

[0031] The resistor voltage divider is used to step down the input common mode voltage, and input the stepped-down voltage to the comparator 5, so that the comparator 5 compares the stepped-down voltage.

[0032] Specifically, the voltage output by the first resistor 1 may be recorded as the output voltage Va, and the voltage output by the third resistor 3 may be recorded as the output voltage Vb. The comparator 5 is used to compare the output voltage Va with the output voltage Vb.

[0033] The resistor divider reduces the high voltage of the first input common mode voltage and / or the second input common mode voltage to within the input voltage range of the comparator 5, generally reducing the high voltage of the first input common mode voltage and / or the second input common mode voltage to 0-3.3V or 0-5V.

[0034] In some embodiments, the first resistor 1 and the third resistor 3 have the same resistance value, and the second resistor 2 and the fourth resistor 4 have the same resistance value.

[0035] At this time, the calculation formulas of the output voltage Va and the output voltage Vb are as follows: .

[0036] Furthermore, the receiver circuit also includes a negative feedback amplifier 6, a positive input terminal of the negative feedback amplifier 6 is connected to a fixed reference voltage, a negative input terminal of the negative feedback amplifier 6 is connected to the output terminal of the first resistor 1 and the output terminal of the third resistor 3, and an output terminal of the negative feedback amplifier 6 is connected to a reference node of the resistor divider; the negative feedback amplifier 6 is configured to dynamically adjust the output voltage of the negative feedback amplifier 6 according to the output voltage of the output terminal of the first resistor 1 and / or the third resistor 3 and the negative feedback mechanism.

[0037] Among them, the output voltage of the negative feedback amplifier 6 can be recorded as the output voltage VCM, the fixed reference voltage is recorded as Vref, the negative input terminal detects the output voltage Va and the output voltage Vb, and the negative feedback amplifier 6 generates a corresponding output voltage VCM as the reference voltage of the resistor divider by comparing the output voltage Va or the output voltage Vb with the fixed reference voltage.

[0038] The function of the negative feedback amplifier 6 is to reduce the output voltage VCM when it is detected that the output voltage Va and / or the output voltage Vb have a larger value; and to increase the output voltage VCM when it is detected that the output voltage Va and / or the output voltage Vb have a smaller value.

[0039] For example, when the common-mode voltage across A / B is relatively large, such as +40V, the output voltage Va / output voltage Vb after voltage division increases accordingly. At this time, the negative feedback amplifier 6 outputs a lower output voltage VCM, such as +0.2V, thereby reducing the output voltage Va / output voltage Vb so that it is within the voltage range in which the comparator 5 can operate; similarly, when the common-mode voltage across A / B is relatively low, such as -40V, the output voltage Va / output voltage Vb after voltage division decreases accordingly. At this time, the amplifier outputs a higher voltage value, such as +3V, thereby increasing the output voltage Va / output voltage Vb so that it is within the voltage range in which the comparator 5 can operate.

[0040] The negative feedback amplifier 6 may be a conventional negative feedback amplifier circuit structure, and its specific circuit structure is the same as that in the prior art, which will not be described in detail here.

[0041] The output voltage VCM of the negative feedback amplifier 6 is used as a reference voltage of the resistor divider, and can be flexibly adjusted according to the magnitude of the input common mode voltage.

[0042] Among them, the input common mode voltage of the present application is a continuously variable voltage, so the output voltage Va, the output voltage Vb and the output voltage VCM of the negative feedback amplifier 6 are also continuously variable voltages.

[0043] Furthermore, the negative feedback amplifier 6 dynamically adjusts the output voltage of the negative feedback amplifier 6 according to a comparison result between the output voltage of the output terminal of the first resistor 1 or the third resistor 3 and the fixed reference voltage.

[0044] Further, when the negative feedback amplifier 6 determines that the first input common mode voltage and / or the second input common mode voltage is larger according to the comparison result, the output voltage of the negative feedback amplifier 6 is dynamically reduced; When the negative feedback amplifier 6 determines, based on the comparison result, that the first input common mode voltage and / or the second input common mode voltage is smaller, the output voltage of the negative feedback amplifier 6 is dynamically increased.

[0045] Furthermore, the receiver circuit further comprises an adjustable current source 7 , a positive electrode of the adjustable current source 7 is connected to the output end of the third resistor 3 , and a negative electrode of the current source is grounded.

[0046] The receiver circuit further includes an electronic fuse (efuse), which is used to control the adjustable current source 7 .

[0047] The adjustable current source 7 is used to compensate for the threshold offset caused by changes in chip technology, power supply, temperature, etc.

[0048] Furthermore, the input voltage of the comparator 5 is in the range of ground voltage to power supply voltage.

[0049] Among them, after the negative feedback amplifier 6 is added to the receiver circuit of the present application, the input range of the first input common mode voltage and the second input common mode voltage is ±40V.

[0050] Further, the receiver circuit can be applied to RS-485 / RS-422 interface chip.

[0051] A receiver circuit of the present invention uses a negative feedback amplifier 6 to generate a variable reference level for an input resistor voltage divider circuit, thereby widening the voltage range that the receiver circuit can handle, that is, widening the input common-mode voltage range of the RS-485 / RS-422 receiver from -7V to +12V to ±40V, so that it can work normally under an input wide common-mode range voltage and can maintain a receiver threshold of -200mV to -50mV, that is, maintaining a narrow threshold voltage range.

[0052] The present invention also provides a chip, comprising any receiver circuit as described above.

[0053] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the product embodiment described later, since it corresponds to the method, the description is relatively simple, and the relevant parts can be referred to the partial description of the system embodiment.

[0054] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A receiver circuit, comprising a resistor divider and a comparator, wherein the resistor divider comprises a first resistor, a second resistor, a third resistor and a fourth resistor, wherein an overall input terminal of the first resistor and the second resistor connected in series is connected to a first input common mode voltage, an overall input terminal of the third resistor and the fourth resistor connected in series is connected to a second input common mode voltage, an overall output terminal of the first resistor and the second resistor connected in series and an overall output terminal of the third resistor and the fourth resistor connected in series are connected to each other to form a reference node of the resistor divider, a positive input terminal of the comparator is connected to an output terminal of the first resistor, and a negative input terminal is connected to an output terminal of the third resistor, wherein: The receiver circuit further comprises a negative feedback amplifier, wherein a positive input terminal of the negative feedback amplifier is connected to a fixed reference voltage, a negative input terminal of the negative feedback amplifier is connected to an output terminal of the first resistor and an output terminal of the third resistor, and an output terminal of the negative feedback amplifier is connected to a reference node of the resistor divider; The negative feedback amplifier is configured to dynamically adjust the output voltage of the negative feedback amplifier according to the output voltage of the output terminal of the first resistor and / or the third resistor and a negative feedback mechanism.

2. The receiver circuit according to claim 1, characterized in that The receiver circuit further includes an adjustable current source, a positive electrode of the adjustable current source is connected to the output end of the third resistor, and a negative electrode of the current source is grounded.

3. The receiver circuit according to claim 2, characterized in that The receiver circuit also includes an electronic fuse for controlling the adjustable current source.

4. The receiver circuit according to any one of claims 1 to 3, characterized in that: The input voltage of the comparator ranges from ground voltage to power supply voltage.

5. The receiver circuit according to any one of claims 1 to 3, characterized in that: The negative feedback amplifier dynamically adjusts the output voltage of the negative feedback amplifier according to a comparison result between the output voltage of the output end of the first resistor or the third resistor and the fixed reference voltage.

6. The receiver circuit according to claim 5, characterized in that When the negative feedback amplifier determines, according to the comparison result, that the first input common mode voltage and / or the second input common mode voltage is larger, the output voltage of the negative feedback amplifier is dynamically reduced; When the negative feedback amplifier determines, based on the comparison result, that the first input common-mode voltage and / or the second input common-mode voltage is smaller, the output voltage of the negative feedback amplifier is dynamically increased.

7. The receiver circuit according to any one of claims 1 to 3, characterized in that: The output voltages of the first resistor and the third resistor, and the output voltage of the negative feedback amplifier are all continuously changing voltages.

8. The receiver circuit according to any one of claims 1 to 3, characterized in that: The range of the first input common mode voltage and the second input common mode voltage is ±40V.

9. The receiver circuit according to any one of claims 1 to 3, characterized in that: The receiver circuit is applied to an RS-485 interface chip.

10. A chip, characterized in that: Comprising a receiver circuit as described in any one of claims 1 to 9.

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