Bus drivers and communication interfaces

Abstract

This invention discloses a bus driver and a communication interface. The bus driver includes a differential circuit and a common-mode feedback circuit. The differential circuit generates a differential signal based on the input transmission signal. The common-mode feedback circuit is connected to the differential circuit and adjusts the current of the differential signal based on the differential signal and a preset voltage value. This ensures that the common-mode voltage remains stable at the preset voltage value, reducing electromagnetic interference caused by common-mode voltage fluctuations on the bus. Simultaneously, it reduces the impact of the common-mode voltage on the current of the differential signal, ensuring the output amplitude from the bus driver to the receiver, improving the reliability of the bus driver, and increasing the common-mode operating range of the bus driver.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a bus driver and a communication interface. Background Technology

[0002] The communication interface includes a bus driver and at least one receiver. Signals can be transmitted from the bus driver to the receiver via a differential bus to achieve communication. A pair of differential buses can include multiple communication nodes. Different communication nodes have different ground voltages, resulting in a common-mode voltage difference between them. The bus driver has current-limiting protection; when the common-mode voltage difference is large, the common-mode resistor will draw too much current, making the current output from the bus driver to the receiver very small. This results in insufficient output amplitude from the bus driver to the receiver, meaning the common-mode operating range of the bus driver is relatively small. For example, when the communication interface is an RS485 communication interface, there can be 256 communication nodes on the differential bus, and the input impedance of the receiver is greater than or equal to 96kΩ. When the bus driver's power supply voltage is 5V and the common-mode voltage is -30V, the current drawn by the common-mode resistor is (30+2.5) / 0.375=86.7mA. Therefore, the current output from the bus driver to the receiver is very small, making it impossible for the bus driver to transmit signals normally under the current common-mode voltage; that is, the bus driver cannot support the current common-mode range. Summary of the Invention

[0003] This invention provides a bus driver and communication interface, which improves the common-mode operating range of the bus driver.

[0004] In a first aspect, embodiments of the present invention provide a bus driver, including a differential circuit and a common-mode feedback circuit;

[0005] The differential circuit is used to generate a differential signal based on the input transmission signal; the common-mode feedback circuit is connected to the differential circuit, and the common-mode feedback circuit is used to adjust the current of the differential signal based on the differential signal and a preset voltage value.

[0006] Optionally, the common-mode feedback circuit includes a sampling unit and a feedback adjustment unit;

[0007] The sampling unit is connected to the differential circuit and is used to generate a common-mode signal based on the differential signal. The feedback adjustment unit is connected to the sampling unit and is used to pull down the current of the differential signal when the voltage of the common-mode signal is greater than the preset voltage value, and to pull up the current of the differential signal when the voltage of the common-mode signal is less than the preset voltage value.

[0008] Optionally, the differential circuit includes two differential units, and the differential signal includes a first differential signal and a second differential signal; the input terminal of each differential unit is used to input the transmitted signal; one differential unit is used to output the first differential signal according to the transmitted signal, and the other differential unit is used to output the second differential signal according to the transmitted signal.

[0009] The sampling unit includes two sampling modules, and the feedback adjustment unit includes two feedback adjustment modules. The input terminal of each sampling module is connected to the output terminal of one of the differential units. The output terminal of each sampling module is then connected to the first input terminal of each feedback adjustment module. The second input terminal of each feedback adjustment module is used to input the preset voltage value. The first output terminal of each feedback adjustment module is connected to the output terminal of one of the differential units, and the second output terminal of each feedback adjustment module is connected to the output terminal of the other differential unit. The power supply terminal of one feedback adjustment module is connected to the first power supply terminal, and the power supply terminal of the other feedback adjustment module is grounded. The two sampling modules are used to equalize the voltage of the first differential signal and the second differential signal to form the common-mode signal. One feedback adjustment module is used to pull down the output current of the two differential units when the voltage of the common-mode signal is greater than the preset voltage value. The other feedback adjustment module is used to pull up the output current of the two differential units when the voltage of the common-mode signal is less than the preset voltage value.

[0010] Optionally, each of the sampling modules includes a sampling resistor, and the resistance values ​​of the sampling resistors in the two sampling modules are equal.

[0011] Optionally, each of the feedback adjustment modules includes a comparator and a switching submodule;

[0012] The positive input terminal of the comparator is used to input the common-mode signal, and the negative input terminal of the comparator is used to input the preset voltage value. The output terminal of the comparator is connected to the control terminal of the switching submodule. The first terminal of one switching submodule is connected to the first power supply terminal, and the first terminal of another switching submodule is grounded. The first output terminal of each switching submodule is connected to the output terminal of one differential unit, and the second output terminal of each switching submodule is connected to the output terminal of another differential unit. The voltage of the first power supply provided by the first power supply terminal is greater than 0V. One switching submodule is used to connect its first output terminal and the ground, and its second output terminal and the ground, respectively, when the voltage of the common-mode signal is greater than the preset voltage value. Another switching submodule is used to connect its first output terminal and the first power supply terminal, and its second output terminal and the first power supply terminal, respectively, when the voltage of the common-mode signal is less than the preset voltage value.

[0013] Optionally, one of the switching submodules includes a first N-type switching transistor and a second N-type switching transistor; the gates of the first N-type switching transistor and the second N-type switching transistor are connected to the output terminal of the comparator, the first terminals of the first N-type switching transistor and the second N-type switching transistor are grounded, the second terminal of the first N-type switching transistor serves as the first output terminal of the switching submodule, and the second terminal of the second N-type switching transistor serves as the second output terminal of the switching submodule;

[0014] And / or, another of the switching submodules includes a first P-type switching transistor and a second P-type switching transistor; the gates of the first P-type switching transistor and the second P-type switching transistor are connected to the output terminal of the comparator, the first terminals of the first P-type switching transistor and the second P-type switching transistor are connected to the first power supply terminal, the second terminal of the first P-type switching transistor serves as the first output terminal of the switching submodule, and the second terminal of the second P-type switching transistor serves as the second output terminal of the switching submodule.

[0015] Optionally, each of the feedback regulation modules further includes a current source; the first terminal of the switching submodule is connected to the first power supply terminal or the ground via one of the current sources.

[0016] Optionally, the reference currents provided by the different current sources are equal.

[0017] Optionally, the differential unit includes a differential signal generation module and a high-voltage protection module; the output terminal of the differential unit includes a first differential signal output terminal and a second differential signal output terminal; the input terminal of the differential signal generation module is used to input the transmission signal, the output terminal of the differential signal generation module is used to output the differential signal, the input terminal of the high-voltage protection module is connected to the output terminal of the differential signal generation module, and the output terminal of the high-voltage protection module serves as the output terminal of the bus driver;

[0018] The input terminal of the sampling module is connected to either the first differential signal output terminal or the second differential signal output terminal, and the first and second output terminals of the feedback adjustment module are both connected to the first differential signal output terminal.

[0019] Secondly, embodiments of the present invention provide a communication interface, including the bus driver described in the first aspect and at least one receiver; the bus driver is connected to the receiver via a differential bus.

[0020] The technical solution of this invention, by setting a common-mode feedback circuit to adjust the current of the differential signal based on the differential signal and a preset voltage value, ensures that the common-mode voltage remains stable at the preset voltage value, reducing electromagnetic radiation interference on the bus caused by common-mode voltage fluctuations. Simultaneously, it reduces the impact of the common-mode voltage on the current of the differential signal, ensuring the output amplitude from the bus driver to the receiver, improving the reliability of the bus driver, and increasing the common-mode operating range of the bus driver. Attached Figure Description

[0021] Figure 1 A schematic diagram of a bus driver provided in an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of another bus driver provided in an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of another bus driver provided in an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of another bus driver provided in an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of another bus driver provided in an embodiment of the present invention;

[0026] Figure 6 A schematic diagram of another bus driver provided in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of another bus driver provided in an embodiment of the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0029] Figure 1 This is a schematic diagram of a bus driver provided in an embodiment of the present invention. Figure 1 As shown, the bus driver includes a differential circuit 10 and a common-mode feedback circuit 20; the differential circuit 10 is used to form a differential signal based on the input transmission signal; the common-mode feedback circuit 20 is connected to the differential circuit 10 and is used to adjust the current of the differential signal based on the differential signal and a preset voltage value.

[0030] Specifically, the input terminal of the differential circuit 10 is used to input the transmission signal. The differential circuit 10 can generate a differential signal based on the transmission signal. The differential signal includes a first differential signal and a second differential signal. The common-mode feedback circuit 20 is connected to the differential circuit 10 and is used to receive the differential signal and determine the common-mode voltage of the differential signal based on the differential signal. The common-mode voltage of the differential signal is half of the sum of the voltages of the first differential signal and the second differential signal. At this time, the common-mode voltage of the differential signal is the actual common-mode voltage of the bus driver. For example, when the first differential signal is 4V and the second differential signal is 1V, the common-mode voltage of the first differential signal and the second differential signal is (4+1) / 2=2.5V. The preset voltage value can be set according to the reference common-mode voltage of the bus driver. The reference common-mode voltage of the bus driver is half of the bus driver power supply voltage. For example, the preset voltage value can be equal to the reference common-mode voltage of the bus driver. When the bus driver's power supply voltage is 5V, the bus driver's reference common-mode voltage is 5 / 2 = 2.5V, and the preset voltage value can be 2.5V. The differential signal current is the output current when the differential circuit 10 outputs the differential signal. The differential signal current includes the current of the differential circuit 10 itself when outputting the differential signal, and the sum of the current acting on the common-mode resistor by the common-mode voltage. When the common-mode voltage is greater than the preset voltage value, the direction of the current acting on the common-mode resistor is towards the bus driver, that is, the current acting on the common-mode resistor by the common-mode voltage is injected into the bus driver, increasing the differential signal current. At this time, the common-mode feedback circuit 20 can adjust the differential signal current to reduce the differential signal current. When the common-mode voltage is less than the preset voltage value, the direction of the current acting on the common-mode resistor is towards the bus driver, that is, the common-mode voltage draws current from the differential signal and acts on the common-mode resistor, reducing the differential signal current. At this time, the common-mode feedback circuit 20 can adjust the differential signal current to increase the differential signal current. This ensures that the common-mode voltage remains stable at the preset value, reducing electromagnetic interference caused by common-mode voltage fluctuations on the bus. Simultaneously, it reduces the impact of common-mode voltage on the differential signal current, guaranteeing the output amplitude from the bus driver to the receiver, improving the reliability of the bus driver, and increasing the common-mode operating range of the bus driver.

[0031] The technical solution in this embodiment uses a common-mode feedback circuit to adjust the current of the differential signal based on the differential signal and a preset voltage value, ensuring that the common-mode voltage remains stable at the preset value. This reduces electromagnetic interference caused by common-mode voltage fluctuations on the bus. Simultaneously, it reduces the impact of the common-mode voltage on the differential signal current, ensuring the output amplitude from the bus driver to the receiver, improving the reliability of the bus driver, and increasing the common-mode operating range of the bus driver.

[0032] Figure 2This is a schematic diagram of another bus driver structure provided in an embodiment of the present invention. Figure 2 As shown, the common-mode feedback circuit 20 includes a sampling unit 21 and a feedback adjustment unit 22. The sampling unit 21 is connected to the differential circuit 10 and is used to generate a common-mode signal based on the differential signal. The feedback adjustment unit 22 is connected to the sampling unit 21 and is used to pull down the current of the differential signal when the voltage of the common-mode signal is greater than a preset voltage value, and to pull up the current of the differential signal when the voltage of the common-mode signal is less than the preset voltage value.

[0033] Specifically, sampling unit 21 can simultaneously acquire the first differential signal and the second differential signal from the differential signal, and determine the common-mode signal based on the sum of the voltages of the first differential signal and the second differential signal. At this time, the common-mode signal is the common-mode voltage of the current differential signal. After sampling unit 21 forms the common-mode signal based on the differential signal, the common-mode signal is output to feedback adjustment unit 22. Feedback adjustment unit 22 compares the voltage of the common-mode signal with a preset voltage value. When the voltage of the common-mode signal is greater than the preset voltage value, the current of the differential signal increases. At this time, feedback adjustment unit 22 provides a discharge path for differential circuit 10, allowing the current of the differential signal to discharge through the discharge path, thus pulling down the current of the differential signal. When the voltage of the common-mode signal is less than the preset voltage value, the current of the differential signal decreases. At this time, feedback adjustment unit 22 provides a charging current for differential circuit 10, thus pulling up the current of the differential signal. This ensures that the common-mode voltage remains stable at the preset voltage value, reducing electromagnetic radiation interference on the bus caused by common-mode voltage fluctuations. At the same time, it can reduce the impact of common-mode voltage on the current of differential signal, ensure the output amplitude of bus driver to receiver, improve the reliability of bus driver, and increase the common-mode operating range of bus driver.

[0034] Figure 3 This is a schematic diagram of another bus driver structure provided in an embodiment of the present invention. Figure 3As shown, the differential circuit 10 includes two differential units 11, and the differential signal DO includes a first differential signal DO1 and a second differential signal DO2. The input terminal of each differential unit 11 is used to input the transmission signal DI. One differential unit 11 is used to output the first differential signal DO1 according to the transmission signal DI, and the other differential unit 11 is used to output the second differential signal DO2 according to the transmission signal DI. The sampling unit 21 includes two sampling modules 211, and the feedback adjustment unit 22 includes two feedback adjustment modules 221. The input terminal of each sampling module 211 is connected to the output terminal of one differential unit 11. After the output terminal of each sampling module 211 is connected, it is connected to the first input terminal IN1 of each feedback adjustment module 221, and the second input terminal IN2 of each feedback adjustment module 221 is connected to the second input terminal IN2 of each feedback adjustment module 221. Used to input a preset voltage value; the first output terminal OUT1 of each feedback adjustment module 221 is connected to the output terminal of one differential unit 11, the second output terminal OUT2 of each feedback adjustment module 221 is connected to the output terminal of another differential unit 11, the power supply terminal of one feedback adjustment module 221 is connected to the first power supply terminal VDD1, and the power supply terminal of the other feedback adjustment module 221 is grounded to GND; two sampling modules 211 are used to equalize the voltage of the first differential signal and the second differential signal to form a common-mode signal; one feedback adjustment module 221 is used to pull down the output current of the two differential units 11 when the voltage of the common-mode signal is greater than the preset voltage value; the other feedback adjustment module 221 is used to pull up the output current of the two differential units 11 when the voltage of the common-mode signal is less than the preset voltage value.

[0035] Specifically, the input terminal of each sampling module 211 is connected to the output terminal of a differential unit 11. The input signal of one sampling module 211 is the first differential signal DO1, and the first differential signal DO1 is sampled, such that the voltage of the first sampled signal output by the sampling module 211 is positively correlated with the voltage of the first differential signal DO1. The input signal of the other sampling module 211 is the second differential signal DO2, and the second differential signal DO2 is sampled, such that the voltage of the second sampled signal output by the sampling module 211 is positively correlated with the voltage of the second differential signal DO2. The output terminals of the two sampling modules 211 are connected. At this time, the voltage at the output terminals of the two sampling modules 211 is the average voltage of the first and second sampled signals. That is, the voltage of the common-mode signal is positively correlated with the average of the sum of the voltages of the first differential signal DO1 and the second differential signal DO2, thus allowing the common-mode signal to characterize the common-mode voltage of the differential signal.

[0036] When a common-mode signal is input to the first input terminal IN1 of both feedback adjustment modules 221, and a preset voltage value is input to the second input terminal IN2 of both feedback adjustment modules 221, each feedback adjustment module 221 can compare the voltage of the common-mode signal with the preset voltage value. The voltage of the first power supply provided by the first power supply terminal VDD1 is greater than 0V provided by ground GND. For example, the voltage of the first power supply can be 5V. When the power supply terminal of the first feedback adjustment module 221 is connected to the first power supply terminal VDD1, and the power supply terminal of the second feedback adjustment module 221 is grounded to GND, when the voltage of the common-mode signal is greater than the preset voltage value, the first feedback adjustment module 221 disconnects its power supply terminal and any output terminal, and the second feedback adjustment module 221 can connect its power supply terminal and both output terminals. That is, the second feedback adjustment module 221 can provide a discharge path to ground GND for the output terminals of the two differential units 11, reducing the current of the differential signals output by the two differential units 11. When the common-mode signal voltage is less than a preset voltage value, the first feedback adjustment module 221 connects its power supply terminal and two output terminals, while the second feedback adjustment module 221 disconnects its power supply terminal and either output terminal. This means the first feedback adjustment module 221 can provide a charging path from the output terminals of the two differential units 11 to the first power supply terminal VDD1, allowing VDD1 to provide charging current to the output terminals of the differential units 11, thus increasing the current of the differential signals output by the two differential units 11. This ensures that the common-mode voltage remains stable at the preset voltage value, reducing electromagnetic interference caused by common-mode voltage fluctuations on the bus. Simultaneously, it reduces the impact of the common-mode voltage on the differential signal current, ensuring the output amplitude from the bus driver to the receiver, improving the reliability of the bus driver, and increasing the common-mode operating range of the bus driver.

[0037] Figure 4 This is a schematic diagram of another bus driver structure provided in an embodiment of the present invention. Figure 4 As shown, each sampling module 211 includes a sampling resistor R1, and the resistance values ​​of the sampling resistors R1 in the two sampling modules 211 are equal.

[0038] Specifically, the sampling resistor R1 is used to sample the differential signal, so that the voltage of the sampled signal output by each sampling module 211 is positively correlated with the voltage of the corresponding differential signal. The sampling resistors R1 in the two sampling modules 211 have the same resistance value, which can realize the average sampling of the first differential signal DO1 and the second differential signal DO2, thereby enabling the common-mode signal to characterize the common-mode voltage.

[0039] Continue to refer to Figure 4Each feedback regulation module 221 includes a comparator AMP and a switching submodule 2211. The positive input terminal of the comparator AMP is used to input a common-mode signal, and the negative input terminal of the comparator AMP is used to input a preset voltage value. The output terminal of the comparator AMP is connected to the control terminal of the switching submodule 2211. The first terminal of one switching submodule 2211 is connected to the first power supply terminal VDD1, and the first terminal of one switching submodule 2211 is grounded to GND. The first output terminal of each switching submodule 2211 is connected to the output terminal of a differential unit 11. Each switching submodule 2211... The second output terminal of 211 is connected to the output terminal of another differential unit 11. The voltage of the first power supply provided by the first power supply terminal VDD1 is greater than the 0V provided by ground GND. A switch submodule 2211 is used to connect its first output terminal and ground GND, and its second output terminal and ground GND respectively when the voltage of the common mode signal is greater than a preset voltage value. Another switch submodule 2211 is used to connect its first output terminal and the first power supply terminal VDD1, and its second output terminal and the first power supply terminal VDD1 respectively when the voltage of the common mode signal is less than a preset voltage value.

[0040] Specifically, the first output terminal of each switch submodule 2211 serves as the first output terminal OUT1 of the feedback adjustment module 221, and the second output terminal of each switch submodule 2211 serves as the second output terminal OUT2 of the feedback adjustment module 221. The comparator AMP compares the voltage of the common-mode signal with a preset voltage value. When the voltage of the common-mode signal is greater than the preset voltage value, the comparator AMP outputs a high level. The first switch submodule 2211 disconnects the path between the first power supply terminal VDD1 and the first output terminal based on the high level, and simultaneously disconnects the path between the first power supply terminal VDD1 and the second output terminal. The second switch submodule 2211 connects the path between ground GND and the first output terminal based on the high level, and simultaneously connects the path between ground GND and the second output terminal. At this time, the second switch submodule 2211 provides a discharge path to ground GND for the output terminals of the two differential units 11, reducing the current of the differential signals output by the two differential units 11. When the voltage of the common-mode signal is less than the preset voltage value, the comparator AMP outputs a low level. The first switch submodule 2211 connects the path between the first power supply terminal VDD1 and the first output terminal when the level is low, and simultaneously connects the path between the first power supply terminal VDD1 and the second output terminal. The second switch submodule 2211 disconnects the path between ground GND and the first output terminal when the level is low, and simultaneously disconnects the path between ground GND and the second output terminal. At this time, the first switch submodule 2211 provides a charging path for the first power supply terminal VDD1 to the output terminals of the two differential units 11, so that the first power supply terminal VDD1 provides charging current to the output terminals of the differential units 11, increasing the current of the differential signals output by the two differential units 11. This ensures that the common-mode voltage is always stable at the preset voltage value, reducing electromagnetic radiation interference caused by common-mode voltage fluctuations on the bus. At the same time, it reduces the impact of common-mode voltage on the current of the differential signal, ensures the output amplitude from the bus driver to the receiver, improves the reliability of the bus driver, and increases the common-mode operating range of the bus driver.

[0041] Continue to refer to Figure 4 A switching submodule 2211 includes a first N-type switching transistor MN1 and a second N-type switching transistor MN2; the gates of the first N-type switching transistor MN1 and the second N-type switching transistor MN2 are connected to the output terminal of the comparator AMP; the first terminal of the first N-type switching transistor MN1 and the first terminal of the second N-type switching transistor MN2 are grounded to GND; the second terminal of the first N-type switching transistor MN1 serves as the first output terminal of the switching submodule 2211; and the second terminal of the second N-type switching transistor serves as the second output terminal of the switching submodule 2211.

[0042] Specifically, when the common-mode signal voltage is greater than a preset voltage value, the comparator AMP outputs a high level. The first N-type switch MN1 and the second N-type switch MN2 are turned on, and the outputs of the two differential units 11 are connected to ground GND through the first N-type switch MN1 and the second N-type switch MN2, respectively. That is, the first N-type switch MN1 and the second N-type switch MN2 provide discharge paths to ground GND for the two differential units 11, reducing the current of the differential signals output by the two differential units 11. When the common-mode signal voltage is less than the preset voltage value, the comparator AMP outputs a low level. The first N-type switch MN1 and the second N-type switch MN2 are turned off, thus breaking the path from the two differential units 11 to ground GND. Furthermore, when the first terminals of the first N-type switch MN1 and the second N-type switch MN2 are both connected to a fixed potential ground GND, the conduction level of the first N-type switch MN1 and the second N-type switch MN2 is related to the high-level voltage value output by the comparator AMP. When the common-mode signal voltage is greater than the preset voltage value, and the greater the difference between the two, the greater the high-level voltage output of the comparator AMP. This results in a greater degree of conduction of the first N-type switch MN1 and the second N-type switch MN2, a greater discharge current flowing through the first N-type switch MN1 and the second N-type switch MN2, and a stronger feedback regulation of the common-mode feedback circuit 20. This allows for rapid adjustment of the differential signal current. Conversely, when the common-mode signal voltage is greater than the preset voltage value, and the smaller the difference between the two, the smaller the high-level voltage output of the comparator AMP. This results in a lesser degree of conduction of the first N-type switch MN1 and the second N-type switch MN2, a smaller discharge current flowing through the first N-type switch MN1 and the second N-type switch MN2, and a weaker feedback regulation of the common-mode feedback circuit 20. This allows for accurate adjustment of the differential signal current.

[0043] Continue to refer to Figure 4 Another switching submodule 2211 includes a first P-type switching transistor MP1 and a second P-type switching transistor MP2; the gate of the first P-type switching transistor MP1 and the gate of the second P-type switching transistor MP2 are connected to the output terminal of the comparator AMP, the first terminal of the first P-type switching transistor MP1 and the first terminal of the second P-type switching transistor MP2 are connected to the first power supply terminal VDD1, the second terminal of the first P-type switching transistor MP1 serves as the first output terminal of the switching submodule, and the second terminal of the second P-type switching transistor MP2 serves as the second output terminal of the switching submodule.

[0044] Specifically, when the common-mode signal voltage is less than a preset voltage value, the comparator AMP outputs a low level. The first P-type switch MP1 and the second P-type switch MP2 are turned on, and the outputs of the two differential units 11 are connected to the first power supply terminal VDD1 through the first P-type switch MP1 and the second P-type switch MP2, respectively. That is, the first P-type switch MP1 and the second P-type switch MP2 provide charging paths from the first power supply terminal VDD1 to the outputs of the two differential units 11, allowing the first power supply terminal VDD1 to provide charging current to the outputs of the differential units 11, increasing the current of the differential signals output by the two differential units 11. When the common-mode signal voltage is greater than the preset voltage value, the comparator AMP outputs a high level. The first P-type switch MP1 and the second P-type switch MP2 are turned off, thus breaking the path from the two differential units 11 to the first power supply terminal VDD1. Furthermore, when the first terminals of the first P-type switch MP1 and the second P-type switch MP2 are both connected to the fixed potential of the first power supply terminal VDD1, the conduction degree of the first P-type switch MP1 and the second P-type switch MP2 is related to the low-level voltage value output by the comparator AMP. When the voltage of the common-mode signal is less than the preset voltage value, and the greater the difference between the two, the lower the low-level voltage output by the comparator AMP, the greater the conduction degree of the first P-type switch MP1 and the second P-type switch MP2, the greater the charging current flowing through the first P-type switch MP1 and the second P-type switch MP2, and the stronger the feedback regulation degree of the common-mode feedback circuit 20, thereby enabling rapid regulation of the differential signal current. When the voltage of the common-mode signal is less than the preset voltage value, and the smaller the difference between the two, the higher the low-level voltage output by the comparator AMP, the less the conduction degree of the first P-type switch MP1 and the second P-type switch MP2, the smaller the charging current flowing through the first P-type switch MP1 and the second P-type switch MP2, and the weaker the feedback regulation degree of the common-mode feedback circuit 20, so that the current of the differential signal can be accurately adjusted.

[0045] Figure 5 This is a schematic diagram of another bus driver structure provided in an embodiment of the present invention. Figure 5 As shown, each feedback regulation module 221 also includes a current source Ib; the first terminal of the switching submodule 2211 is connected to the first power supply terminal VDD1 or ground GND through a current source Ib.

[0046] Specifically, such as Figure 5As shown, the first terminal of a switching submodule 2211 is connected to the first power supply terminal VDD1 via a current source Ib. When the switching submodule 2211 connects the charging path between the first power supply terminal VDD1 and the output terminals of the two differential units 11, the current source Ib can limit the maximum charging current on the charging path, thereby achieving current limiting of the differential unit 11 and realizing overcurrent protection for the bus driver. When a switching submodule 2211 includes a first P-type switch MP1 and a second P-type switch MP2, under the control of the low level output of the comparator AMP, when the conduction degree of the first P-type switch MP1 and the second P-type switch MP2 reaches its maximum, the charging current on the charging path is the reference current provided by the current source Ib. When under the control of the high level output of the comparator AMP, when the conduction degree of the first P-type switch MP1 and the second P-type switch MP2 does not reach its maximum, the charging current on the charging path is less than the reference current provided by the current source Ib.

[0047] Another switching submodule 2211 has its first terminal grounded to GND via a current source Ib. When the switching submodule 2211 is connected to the discharge path between ground GND and the output terminals of the two differential units 11, the current source Ib can limit the maximum discharge current on the discharge path, thereby achieving current limiting of the differential unit 11 and realizing overcurrent protection for the bus driver. When a switching submodule 2211 includes a first N-type switch MN1 and a second N-type switch MN2, under the control of the high level output of the comparator AMP, when the conduction degree of the first N-type switch MN1 and the second N-type switch MN2 reaches its maximum, the discharge current on the discharge path is the reference current provided by the current source Ib. When the conduction degree of the first N-type switch MN1 and the second N-type switch MN2 does not reach its maximum under the control of the high level output of the comparator AMP, the discharge current on the discharge path is less than the reference current provided by the current source Ib.

[0048] Continue to refer to Figure 5 Since the reference current provided by different current sources Ib is equal, the current limiting degree of different differential units 11 can be the same, thereby improving the current limiting reliability of the bus driver.

[0049] Figure 6 This is a schematic diagram of another bus driver structure provided in an embodiment of the present invention. Figure 6As shown, the differential unit 11 includes a differential signal generation module 111 and a high-voltage protection module 112; the output terminals of the differential unit 11 include a first differential signal output terminal LV1 and a second differential signal output terminal LV2. The input terminal of the differential signal generation module 111 is used to input the transmission signal DI, and the output terminal of the differential signal generation module 111 is used to output the differential signal DO. The input terminal of the high-voltage protection module 112 is connected to the output terminal of the differential signal generation module 111, and the output terminal of the high-voltage protection module 112 serves as the output terminal of the bus driver. The input terminal of the sampling module 211 is connected to either the first differential signal output terminal LV1 or the second differential signal output terminal LV2. The first output terminal and the second output terminal of the feedback adjustment module 221 are both connected to the first differential signal output terminal LV1.

[0050] Specifically, the first differential signal output terminal LV1 is the output terminal of the differential signal generation module 111, and the second differential signal output terminal LV2 is the output terminal of the high-voltage protection module 112. The high-voltage protection module 112 is connected to the output terminal of the bus driver and the output terminal of the differential unit 11, which can prevent the transmission of high voltage input from the outside of the bus driver to the differential signal generation module 111, thereby realizing high-voltage protection for the bus driver. The differential signal DO output from the first differential signal output terminal LV1 remains a differential signal DO after passing through the high-voltage protection module 112. At this time, the input terminal of the sampling module 211 can be connected to either the first differential signal output terminal LV1 or the second differential signal output terminal LV2, and sampling of the differential signal DO can be realized in both cases. When the input terminal of the sampling module 211 is connected to the first differential signal output terminal LV1, high voltage can be avoided in the differential signal DO, thereby avoiding the need for the common-mode feedback circuit 20 to set up a high-voltage protection function, simplifying the structure of the bus driver. When the input terminal of the sampling module 211 is connected to the second differential signal output terminal LV2, the consistency between the differential signal sampled by the sampling module 211 and the differential signal output by the bus driver can be improved, thereby improving the accuracy of feedback regulation.

[0051] It should be noted that the bus driver includes two differential units 11, each of which includes a first differential signal output terminal LV1 and a second differential signal output terminal LV2. Therefore, the bus driver includes two first differential signal output terminals LV1 and two second differential signal output terminals LV2. One of the first differential signal output terminals LV1 and the other of the second differential signal output terminals LV2 are used to output the first differential signal DO1 in the differential signal DO, and the other of the first differential signal output terminals LV1 and the other of the second differential signal output terminals LV2 are used to output the second differential signal DO2 in the differential signal DO.

[0052] The structure of the differential unit 11 varies depending on the application scenario of the bus driver. For example, when the bus driver is used for RS485 or RS422 buses, each differential unit 11 includes two power switching transistors. See also: Figure 6 The transmitted signal DI is a differential signal, comprising a first transmitted signal DI1 and a second transmitted signal DI2. One differential unit 11 includes a first high-side drive circuit and a first P-type power device MP3, as well as a first low-side drive circuit and a first N-type power device MN3, used to generate a first differential signal DO1 based on the first transmitted signal DI1. At this time, one first differential signal output terminal LV1 is the connection point between the first P-type power device MP3 and the first N-type power device MN3. Another differential unit 11 includes a second high-side drive circuit and a second P-type power device MP4, as well as a second low-side drive circuit and a second N-type power device MN4, used to generate a second differential signal DO2 based on the second transmitted signal DI2. At this time, another first differential signal output terminal LV1 is the connection point between the second P-type power device MP4 and the second N-type power device MN4. The input terminal of the sampling module 211 is connected to either the first differential signal output terminal LV1 or the second differential signal output terminal LV2.

[0053] For example, when the application scenario of the bus driver is a CAN bus, each differential unit 11 includes a power switch. Figure 7 This is a schematic diagram of another bus driver structure provided in an embodiment of the present invention. Figure 7 As shown, one differential unit 11 includes a high-side drive circuit and a P-type power device MP5, used to form a first differential signal DO1 based on the transmitted signal DI. At this time, one first differential signal output terminal LV1 is the second terminal of the P-type power device MP5. Another differential unit 11 includes a low-side drive circuit and an N-type power device MN5, used to form a second differential signal DO2 based on the transmitted signal DI. At this time, another first differential signal output terminal LV1 is the second terminal of the N-type power device MN5. The input terminal of the sampling module 211 is connected to either the first differential signal output terminal LV1 or the second differential signal output terminal LV2.

[0054] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A bus driver, characterized by The differential circuit and the common-mode feedback circuit are included; The differential circuit is used for forming a differential signal according to an input transmission signal; the common-mode feedback circuit is connected with the differential circuit, and the common-mode feedback circuit is used for adjusting a current of the differential signal according to the differential signal and a preset voltage value; The common-mode feedback circuit includes a sampling unit and a feedback adjusting unit; The sampling unit is connected with the differential circuit, and the sampling unit is used for forming a common-mode signal according to the differential signal; the feedback adjusting unit is connected with the sampling unit, and the feedback adjusting unit is used for pulling down the current of the differential signal when a voltage of the common-mode signal is greater than the preset voltage value, and pulling up the current of the differential signal when the voltage of the common-mode signal is less than the preset voltage value; The differential circuit includes two differential units, and the differential signal includes a first differential signal and a second differential signal; an input end of each differential unit is used for inputting the transmission signal; One differential unit is used for outputting the first differential signal according to the transmission signal, and another differential unit is used for outputting the second differential signal according to the transmission signal; The sampling unit includes two sampling modules, and the feedback adjusting unit includes two feedback adjusting modules; an output end of each sampling module is connected with an output end of one differential unit, and the output end of each sampling module is connected with a first input end of each feedback adjusting module; a second input end of each feedback adjusting module is used for inputting the preset voltage value; A first output end of each feedback adjusting module is connected with an output end of one differential unit, a second output end of each feedback adjusting module is connected with an output end of another differential unit, a power supply end of one feedback adjusting module is connected with a first power supply end, and a power supply end of another feedback adjusting module is grounded; two sampling modules are used for voltage equalization of the first differential signal and the second differential signal to form the common-mode signal; one feedback adjusting module is used for pulling down output currents of two differential units when a voltage of the common-mode signal is greater than the preset voltage value; and another feedback adjusting module is used for pulling up the output currents of two differential units when the voltage of the common-mode signal is less than the preset voltage value.

2. The bus driver of claim 1, wherein, Each sampling module includes a sampling resistor, and the sampling resistors in two sampling modules have equal resistance values.

3. The bus driver of claim 1, wherein, Each feedback adjusting module includes a comparator and a switch submodule; A positive input end of the comparator is used for inputting the common-mode signal, a negative input end of the comparator is used for inputting the preset voltage value, an output end of the comparator is connected with a control end of the switch submodule, a first end of one switch submodule is connected with the first power supply end, a first end of one switch submodule is grounded, a first output end of each switch submodule is connected with an output end of one differential unit, a second output end of each switch submodule is connected with an output end of another differential unit, and a voltage of a first power supply provided by the first power supply end is greater than 0V. One of the switch sub-modules is configured to connect its first output end to the ground and its second output end to the ground when the voltage of the common mode signal is greater than the preset voltage value; and another of the switch sub-modules is configured to connect its first output end to the first power supply end and its second output end to the first power supply end when the voltage of the common mode signal is less than the preset voltage value.

4. The bus driver of claim 3, wherein, One of the switch sub-modules comprises a first N-type switch tube and a second N-type switch tube; the gate of the first N-type switch tube and the gate of the second N-type switch tube are connected to the output end of the comparator, the first pole of the first N-type switch tube and the first pole of the second N-type switch tube are grounded, the second pole of the first N-type switch tube serves as the first output end of the switch sub-module, and the second pole of the second N-type switch tube serves as the second output end of the switch sub-module; and / or, another of the switch sub-modules comprises a first P-type switch tube and a second P-type switch tube; the gate of the first P-type switch tube and the gate of the second P-type switch tube are connected to the output end of the comparator, the first pole of the first P-type switch tube and the first pole of the second P-type switch tube are connected to the first power supply end, the second pole of the first P-type switch tube serves as the first output end of the switch sub-module, and the second pole of the second P-type switch tube serves as the second output end of the switch sub-module.

5. The bus driver of claim 3, wherein, Each of the feedback adjustment modules further comprises a current source; the first end of the switch sub-module is connected to the first power supply end or the ground through the current source.

6. The bus driver of claim 5, wherein, The reference currents provided by different current sources are equal.

7. The bus driver of claim 1, wherein, The differential unit comprises a differential signal generation module and a high-voltage protection module; the output end of the differential unit comprises a first differential signal output end and a second differential signal output end, the input end of the differential signal generation module is configured to input the transmission signal, the output end of the differential signal generation module is configured to output the differential signal, the input end of the high-voltage protection module is connected to the output end of the differential signal generation module, and the output end of the high-voltage protection module serves as the output end of the bus driver; The input end of the sampling module is connected to the first differential signal output end or the second differential signal output end, and the first output end and the second output end of the feedback adjustment module are both connected to the first differential signal output end.

8. A communication interface, characterized by The bus driver comprises the bus driver and at least one receiver according to any one of claims 1-7; the bus driver is connected to the receiver through a differential bus.

Images