Level conversion circuit and signal testing device

Abstract

The utility model discloses a level conversion circuit and a signal testing device, and the circuit comprises a logic level adjustment module which is connected to a first equipment bidirectional interface through an input end, and is connected to a second level conversion module through an output end; the first level conversion module and the second level conversion module are serially arranged between the first equipment and the second equipment, one end of the first level conversion module is connected to the first equipment bidirectional interface, and one end of the second level conversion module is connected to the output end of the first level conversion module; the other end is connected to the second equipment bidirectional interface; when the circuit is conducted, the logic level adjusting module provides voltage for the second device, and the first level conversion module and the second level conversion module convert a first level of a signal sent by the first device into a second level adaptive to the second device. By adopting the scheme provided by the invention, logic level adjustment and conversion of any level can be realized when the first equipment and the second equipment communicate.

Description

Technical Field

[0001] This application relates to the field of logic level conversion technology, specifically to a level conversion circuit and a signal testing device. Background Technology

[0002] Currently, in the research, development, production, and maintenance of lithium batteries, performance testing is often required. The communication protocols used by the battery management systems in most mobile devices require consistent logic levels between the communicating parties. However, different battery management system components and testing equipment may operate at different voltages, leading to communication problems between the testing equipment and the device under test during testing.

[0003] In related technologies, level conversion chips can be used to solve communication problems between different devices. For example, there is chip A, which is a level converter that supports the I2C bus and supports level conversion of voltage nodes such as 1.8V, 3.3V and 5V. Another example is chip B, which supports level conversion from 3.3V to 5V.

[0004] However, the level conversion chips commonly used in related technologies often only support conversion between two or more specific voltage nodes. They cannot achieve free conversion between arbitrary levels, often failing to meet diverse testing needs, resulting in poor flexibility. Furthermore, different level converters need to be replaced for different tests, leading to reduced testing efficiency. Utility Model Content

[0005] The purpose of this application is to provide a level conversion circuit and a signal testing device. By using a logic level adjustment module, a first level conversion module and a second level conversion module to form a level conversion circuit, the logic level adjustment and level conversion between the test equipment and the device under test can be realized.

[0006] One of the purposes of this application is to provide a level conversion circuit.

[0007] One of the purposes of this application is to provide a signal testing device.

[0008] To achieve one of the above objectives, one embodiment of this application provides a level conversion circuit, comprising:

[0009] A logic level adjustment module is connected to the first device bidirectional interface with its input terminal and to the second level conversion module with its output terminal.

[0010] A first level conversion module and a second level conversion module are serially disposed between a first device and a second device. One end of the first level conversion module is connected to the bidirectional interface of the first device, and one end of the second level conversion module is connected to the output terminal of the first level conversion module, and the other end is connected to the bidirectional interface of the second device.

[0011] When the circuit is turned on, the logic level adjustment module provides voltage to the second device, and the first level conversion module and the second level conversion module convert the first level of the signal sent by the first device into a second level adapted to the second device.

[0012] As a further improvement of this application, the first level conversion module includes a first bidirectional level conversion circuit, and the second level conversion module includes a second bidirectional level transfer circuit;

[0013] The first bidirectional level conversion circuit connects its first signal terminal to the signal terminal of the bidirectional interface of the first device, and connects its first power input terminal to the first logic level, and its second power input terminal to the second logic level.

[0014] The second bidirectional level shifting circuit connects its first signal terminal to the second signal terminal of the first bidirectional level conversion circuit, connects its second signal terminal to the signal terminal of the second device bidirectional interface, connects its first power input terminal to the second logic level, and connects its second power input terminal to the third logic level.

[0015] As a further improvement to this application, the logic level adjustment module includes a third bidirectional level conversion circuit and a programmable resistor;

[0016] The third bidirectional level conversion circuit connects its first power input terminal to the first logic level and its second power input terminal to the second logic level, and connects its first signal terminal to the signal terminal of the bidirectional interface of the first device.

[0017] The programmable resistor is connected to the second logic level via its power interface, and its first signal terminal is connected to the second signal terminal of the third bidirectional level conversion circuit.

[0018] As a further improvement of this application, the logic level adjustment module further includes a driving circuit, which includes an operational amplifier;

[0019] The operational amplifier has its positive input terminal connected to the programmable resistor, its negative input terminal connected to its output terminal, its positive power input terminal connected to the second logic level, and its output terminal connected to the second level conversion module.

[0020] When the circuit is turned on, the driving circuit provides the required driving capability to the second level conversion module.

[0021] As a further improvement to this application, the programmable resistor further includes:

[0022] A variable resistor is connected to the second logic level via its first terminal, grounded via its second terminal, and connected to the positive input of the operational amplifier via its sliding terminal.

[0023] As a further improvement of this application, the logic level adjustment module further includes an inductor, the inductor being connected to the second logic level with its first terminal, connected to the power supply voltage terminal of the drive circuit with its second terminal, and connected to the first terminal of the variable resistor with its second terminal.

[0024] When the circuit is turned on, the inductor element filters out high-frequency noise.

[0025] As a further improvement of this application, the first signal terminal includes a first data terminal and a first clock terminal, and the second signal terminal includes a second data terminal and a second clock terminal.

[0026] As a further improvement to this application, pull-up resistors are provided between the logic level and the first signal terminal and the second signal terminal of each module.

[0027] As a further improvement to this application, the first device is a test machine, and the second device is a test machine.

[0028] As a further improvement of this application, the first logic level is in the range of 0.9V-5V, the second logic level is 5V, and the third logic level is in the range of 0.9V-5V.

[0029] To achieve one of the above objectives, another embodiment of this application provides a signal testing apparatus, characterized in that it includes a tester and a test device, and a level conversion circuit as described in any of the above aspects connected between the tester and the test device.

[0030] Compared with the prior art, the beneficial effects of this application are as follows:

[0031] In this embodiment, a level conversion circuit is formed by combining a logic level adjustment module, a first level conversion module, and a second level conversion module. This allows for logic level conversion and level switching between the first and second devices during communication, thus enabling normal communication between them. Furthermore, the logic level adjustment module converts the logic level of the first device to a logic level compatible with the second device, providing the second level conversion module with a logic level suitable for the second device. This allows the circuit to perform level conversion between any two logic levels. Attached Figure Description

[0032] Figure 1 This illustration shows a schematic diagram of a level conversion circuit provided in an illustrative embodiment of the present application;

[0033] Figure 2 The diagram illustrates a circuit diagram of a first level conversion module and a second level conversion module provided in an illustrative embodiment of this application.

[0034] Figure 3 A circuit diagram of a logic adjustment module provided in an illustrative embodiment of this application is shown;

[0035] Figure 4 A circuit diagram of an I2C signal level conversion circuit provided in an illustrative embodiment of this application is shown.

[0036] Among them, 100 is the first device, 200 is the level conversion circuit, 300 is the second device, 110 is the bidirectional interface of the first device, 210 is the logic level adjustment module, 220 is the first level conversion module, 230 is the second level conversion module, 211 is the third bidirectional level conversion circuit, 221 is the first bidirectional level conversion circuit, 231 is the second bidirectional level conversion circuit, 212 is the programmable resistor, 213 is the drive circuit, 214 is the inductor, and 2131 is the operational amplifier. Detailed Implementation

[0037] The present application will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application, and any structural or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of this application.

[0038] It should be noted that the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," "third," "fourth," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] Please refer to Figure 1 This illustration shows a schematic diagram of a level conversion circuit 200 provided in an illustrative embodiment of the present application, which includes a first device 100, a level conversion circuit 200, and a second device 300. The first device 100 includes a first device bidirectional interface 110, the second device 300 includes a second device bidirectional interface 310, and the level conversion circuit 200 includes a logic level adjustment module 210, a first level conversion module 220, and a second level conversion module 230.

[0040] When the first device 100 communicates with the second device 300, they use the same communication protocol. Optionally, the first device 100 and the second device use the I2C communication protocol.

[0041] The first device bidirectional interface 110 refers to the data line in the communication bus to which the first device 100 is connected, which supports bidirectional data transmission. That is, the first device 100 and the second device 300 can send and receive data through this line. The second device bidirectional interface 310 is similar.

[0042] Optionally, a communication bus may connect multiple first devices 100 and multiple second devices 300.

[0043] Optionally, in the device testing scenario, the first device 100 is the test machine, and the second device 300 is the machine under test.

[0044] The logic levels corresponding to the first device 100 and the second device 300 are different, and the logic level standards corresponding to the first device 100 and the second device 300 are different. For example, the operating voltage of the first device is 3.3V, and the operating voltage of the second device is 5V.

[0045] The level conversion circuit 200 is used to perform signal conversion, converting the signal output by the first device 100 through the first device bidirectional interface 110 into a signal adapted to the logic level of the second device 300. For example, when communicating using the I2C communication protocol, this signal is an I2C signal.

[0046] The logic level adjustment module 210 is connected to the bidirectional interface 110 of the first device via its input terminal and to the second level conversion module 230 via its output terminal. The logic level adjustment module 210 is used to adjust the logic level to obtain the third logic level corresponding to the second device 300. This logic level is connected to the second level conversion module 220, which facilitates the second level conversion module 220 in converting the signal level under the second logic level to the signal level under the third logic level after connecting the second and third logic levels, thereby adapting the signal emitted by the first device to the second device 300.

[0047] In illustrative terms, when the first device 100 and the second device 300 use the I2C communication protocol, I2C signal level conversion is required. In the process of I2C signal level conversion, the first level conversion module 220 first converts the I2C signal under the first logic level to the I2C signal under the second logic level, and then the second level conversion module 230 converts the I2C signal under the second logic level to the I2C signal under the third logic level.

[0048] The first level conversion module 220 and the second level conversion module 230 are serially disposed between the first device 100 and the second device 300. ， A first level conversion module 220 is connected at one end to a first device bidirectional interface 110, and a second level conversion module 230 is connected at one end to the output of the first level conversion module 220 and at the other end to a second device bidirectional interface 310.

[0049] When the circuit is turned on, the logic level adjustment module 210 provides voltage to the second device 300, and the first level conversion module 220 and the second level conversion module 230 convert the first level of the signal sent by the first device 100 into a second level adapted to the second device 300.

[0050] Indicative, such as Figure 1 As shown, when the first device 100 and the second device 300 communicate, after the first device 100 sends a signal, the logic level adjustment module 210 dynamically adjusts the output logic level according to the voltage requirements of the second device 300. The first level conversion module 220 boosts the low-level signal of the first device 100 to an intermediate level, and the second level conversion module 230 converts the intermediate level into a signal of the target level of the second device 300, completing the signal transmission. Furthermore, during reverse transmission, the target level signal sent by the second device 300 is again level-converted by the second level conversion module 230 and the first level conversion module 220 before being transmitted to the first device 100.

[0051] In summary, in this embodiment, by combining the logic level adjustment module, the first level conversion module 220, and the second level conversion module 230 to form a level conversion circuit 200, logic level conversion and level conversion between the first device 100 and the second device 200 are achieved during communication, thereby enabling normal communication between the first device 100 and the second device 200. Furthermore, the logic level adjustment module 210 converts the logic level of the first device 100 to a logic level compatible with the second device 200, thus providing the second level conversion module 230 with a logic level compatible with the second device 200. This allows the circuit to perform level conversion between any two logic levels.

[0052] It should be noted that the solution provided in this application is applicable to bidirectional communication between the first device 100 and the second device 300 under various communication protocols. For ease of understanding, the following embodiments use the I2C communication protocol between the first device 100 and the second device 300 as an example to illustrate this technical solution, and do not limit the implementation scenarios of this solution.

[0053] This is illustrative; please refer to it. Figure 2 The diagram illustrates a circuit diagram of a first level conversion module 220 and a second level conversion module 230 provided in an illustrative embodiment of this application. The first level conversion module 220 includes a first bidirectional level conversion circuit 221, and the second level conversion module 230 includes a second bidirectional level conversion circuit 231.

[0054] If the first level shifting module and the second level shifting module are connected in series, then the first bidirectional level conversion circuit 221 and the second bidirectional level conversion circuit 231 are connected in series.

[0055] The first bidirectional level conversion circuit 221 is connected to the signal terminal of the first device bidirectional interface 110 via its first signal terminal. The second bidirectional level transfer circuit 231 is connected to the second signal terminal of the first bidirectional level conversion circuit 221 via its first signal terminal and to the signal terminal of the second device bidirectional interface 310 via its second signal terminal.

[0056] Optionally, the first signal terminal includes a first data terminal and a first clock terminal, and the second signal terminal includes a second data terminal and a second clock terminal. The first bidirectional level conversion circuit 221 connects its first data terminal SDA1 to the first data terminal SDA1 of the first device bidirectional interface 110, its first clock terminal SCL1 to the first clock terminal SCL1 of the first device bidirectional interface 110, and its second data terminal SDAiso to the first signal terminal SDAB of the second bidirectional level conversion circuit 231, and its second clock terminal SCLiso to the first clock terminal SCLB of the second bidirectional level conversion circuit 231. The second bidirectional level conversion circuit 231 connects its second data terminal SDAA to the data terminal SDAB of the second device bidirectional interface 310, and its second clock terminal SCLA to the clock terminal SCLB of the second device bidirectional interface 310.

[0057] In the first device bidirectional interface 110, there is a power supply voltage pin connected to VCC1 and a ground pin grounded.

[0058] Furthermore, the bidirectional level shifting circuit has two power supply voltage pins, namely the VCCA pin and the VCCB pin. The first bidirectional level shifting circuit 221 connects its first power input terminal (power supply voltage pin) VDD1 to the first logic level VCC1, and its second power input terminal (power supply voltage pin) VDD2 to the second logic level VCC2. The second bidirectional level shifting circuit 231 connects its first power input terminal VCCB to the second logic level VCC2, and its second power input terminal VCCA to the third logic level VCC3.

[0059] Wherein, the first logic level is the voltage corresponding to the first device 100, the second logic level is the intermediate voltage, and the third logic level is the voltage corresponding to the second device 300.

[0060] Optionally, the first logic level ranges from 0.9V to 5V, the second logic level is 5V, and the third logic level ranges from 0.9V to 5V.

[0061] In addition, pull-up resistors are provided between the logic level and the first and second signal terminals of each module.

[0062] In the first level conversion module 220 and the second level conversion module 230, pull-up resistors are provided between the logic level and each signal terminal, that is, pull-up resistors are provided between the logic level and the data terminal and the clock terminal.

[0063] Pull-up resistors connect uncertain signals to logic levels and fix them at a high level. They are mainly used to ensure that signals in a circuit remain at a high level when not driven by external signals, thus ensuring signal stability.

[0064] like Figure 2 It can be seen that a pull-up resistor R6 is provided between the SDA1 pin and the first logic level VCC1, a pull-up resistor R5 is provided between the SCL1 pin and the first logic level VCC1, a pull-up resistor R8 is provided between the SDAB pin and the second logic level VCC2, and a pull-up resistor R7 is provided between the SCLB pin and the second logic level VCC2.

[0065] In addition, both the first and second bidirectional level conversion circuits have a grounded GND pin.

[0066] Please refer to Figure 3 The diagram illustrates a circuit diagram of a logic adjustment module provided in an illustrative embodiment of this application. The logic level adjustment module 210 mainly includes a third bidirectional level conversion circuit 211 and a programmable resistor 212;

[0067] The third bidirectional level conversion circuit 211 is connected to the signal terminal of the first device bidirectional interface 110 via its first signal terminal, and to the first signal terminal of the programmable resistor 212 via its second signal terminal. The output terminal of the programmable resistor 212 is connected to the third logic level.

[0068] Optionally, if the signal terminals include a data terminal and a clock terminal, then the third bidirectional level conversion circuit 211 is connected to the second data terminal SDA0 of the first device bidirectional interface 110 through its first data terminal SDAA, connected to the second clock terminal of the first device bidirectional interface 110 through its first clock terminal SCLA, connected to the data terminal SDA of the programmable resistor 212 through its second data terminal SDAB, and connected to the clock terminal SCL of the programmable resistor 212 through its second clock terminal SCLB.

[0069] Furthermore, both the third bidirectional level shifting circuit 211 and the programmable resistor 212 include power supply voltage pins. The programmable resistor 212 is connected to the second logic level VCC2 via its power interface VDD, and the third bidirectional level shifting circuit 211 is connected to the first logic level VCC1 via its first power input terminal VCCA, and to the second logic level VCC2 via its second power input terminal VCCB.

[0070] Optionally, the logic level adjustment module 210 also includes a driver circuit 213, which includes an operational amplifier 2131. The operational amplifier plays a driving role in the circuit, providing the required driving capability to the second level conversion module 230 when the circuit is turned on. That is, it provides the second level conversion module 230 with the third logic level corresponding to the second device 300, increasing the output driving capability and ensuring more stable data when communicating with the second device 300.

[0071] Operational amplifier 2131 has its positive input terminal +IN connected to programmable resistor 212, and its negative input terminal -IN connected to its output terminal VOUT, forming a feedback loop. Furthermore, its positive power input terminal +VS is connected to the second logic level VCC2, and its output terminal VOUT is connected to the second level conversion module 230 (connected to the VCCA pin of the second bidirectional level conversion circuit 231). Additionally, the inverting power input terminal -VS of operational amplifier 2131 is grounded.

[0072] Optionally, the programmable resistor 212 includes a variable resistor 2121, whose first terminal H pin is connected to the second logic level VCC2, whose second terminal GND pin is grounded, and whose sliding terminal W pin is connected to the positive input terminal +IN pin of the operational amplifier 2131.

[0073] When adjusting the logic level, the level is infinitely adjustable based on the variable resistor 2121. This circuit adjusts the output level of the sliding terminal W pin by changing the resistance value of the variable resistor 2121, and then obtains the third logic level corresponding to the second device 300 through the driving circuit 213.

[0074] Optionally, the logic level adjustment module can achieve stepless adjustment within the range of 0.9-5V.

[0075] Optionally, the voltage resolution of the circuit provided in this application is 0.06V.

[0076] Optionally, the logic level adjustment module 210 further includes an inductor 214, which has its first terminal connected to the second logic level VCC2, its second terminal connected to the power supply voltage terminal +VS pin of the drive circuit 213, and its second terminal connected to the first terminal H pin of the variable resistor 2121.

[0077] When the circuit is on, the inductor 214 filters out high-frequency noise. Filtering by the inductor 214 helps ensure communication stability.

[0078] In addition, pull-up resistors are provided between the signal terminals and the logic levels. A pull-up resistor R2 is provided between the SDAA pin of the third bidirectional level conversion circuit 211 and the first logic level VCC1. A pull-up resistor R1 is provided between the SCLA pin and the first logic level VCC1. A pull-up resistor R4 is provided between the SDA pin of the programmable resistor 212 and the second logic level VCC2. A pull-up resistor R3 is provided between the SCL pin of the programmable resistor 212 and the second logic level VCC2.

[0079] The third bidirectional level transfer circuit and the programmable resistor have a ground pin GND grounded.

[0080] Please refer to Figure 4 The diagram illustrates a circuit diagram of an I2C level conversion circuit provided in an illustrative embodiment of this application. It includes a first bidirectional device interface 110, a first bidirectional level conversion circuit 221, a second bidirectional level conversion circuit 231, a third bidirectional level conversion circuit 211, a programmable resistor 212, an inductor 214, a driver circuit 213, and pull-up resistors R1 to R10.

[0081] When the first device 100 communicates with the second device 300, the first device 100 outputs communication signals and level adjustment signals through the first device bidirectional interface 110, that is, the first device bidirectional interface 110 outputs different I2C signals through different signal interfaces respectively.

[0082] The level adjustment signal is transmitted to the third bidirectional level conversion circuit 211. Subsequently, the logic level adjustment module 210, which consists of the third bidirectional level conversion circuit 211, the programmable resistor 212, the inductor 214 and the drive circuit 213, provides the second bidirectional level conversion circuit 231 with a third logic level that is compatible with the second device 300.

[0083] Subsequently, the I2C signal level is converted based on the first logic level, the second logic level, and the third logic level by the first bidirectional level conversion circuit 221, the second bidirectional level conversion circuit 231, and the peripheral circuit (pull-up resistors R1 to R10) to obtain the I2C signal adapted to the second device 300.

[0084] In another embodiment, this application provides a signal testing device, which includes a tester and a test device, as well as the aforementioned level conversion circuit.

[0085] This device integrates the various components of the aforementioned signal level conversion (such as the driver circuit, bidirectional level conversion circuit, inductor, and programmable resistor) to form a complete level conversion unit. This device enables free signal level conversion between different logic levels when communicating between devices operating at different voltages, thereby ensuring normal communication between different devices.

[0086] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the device and its specific working process described above can be referred to the corresponding process in the aforementioned circuit implementation, and will not be repeated here.

[0087] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0088] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.

Claims

1. A level conversion circuit, characterized in that, It includes a logic level adjustment module, a first level conversion module, and a second level conversion module: A logic level adjustment module is connected to the first device bidirectional interface with its input terminal and to the second level conversion module with its output terminal. A first level conversion module and a second level conversion module are serially disposed between a first device and a second device. One end of the first level conversion module is connected to the bidirectional interface of the first device, and one end of the second level conversion module is connected to the output terminal of the first level conversion module, and the other end is connected to the bidirectional interface of the second device. When the circuit is turned on, the logic level adjustment module provides voltage to the second device, and the first level conversion module and the second level conversion module convert the first level of the signal sent by the first device into a second level adapted to the second device.

2. The level conversion circuit according to claim 1, characterized in that, The first level conversion module includes a first bidirectional level conversion circuit, and the second level conversion module includes a second bidirectional level transfer circuit; The first bidirectional level conversion circuit connects its first signal terminal to the signal terminal of the bidirectional interface of the first device, and connects its first power input terminal to the first logic level, and its second power input terminal to the second logic level. The second bidirectional level shifting circuit connects its first signal terminal to the second signal terminal of the first bidirectional level conversion circuit, connects its second signal terminal to the signal terminal of the second device bidirectional interface, connects its first power input terminal to the second logic level, and connects its second power input terminal to the third logic level.

3. The level conversion circuit according to claim 1, characterized in that, The logic level adjustment module includes a third bidirectional level conversion circuit and a programmable resistor; The third bidirectional level conversion circuit connects its first power input terminal to the first logic level and its second power input terminal to the second logic level, and connects its first signal terminal to the signal terminal of the bidirectional interface of the first device. The programmable resistor is connected to the second logic level via its power interface, and its first signal terminal is connected to the second signal terminal of the third bidirectional level conversion circuit.

4. The level conversion circuit according to claim 3, characterized in that, The logic level adjustment module further includes a driving circuit, which includes an operational amplifier. The operational amplifier has its positive input terminal connected to the programmable resistor, its negative input terminal connected to its output terminal, its positive power input terminal connected to the second logic level, and its output terminal connected to the second level conversion module. When the circuit is turned on, the driving circuit provides the required driving capability to the second level conversion module.

5. The level conversion circuit according to claim 4, characterized in that, The programmable resistor further includes: A variable resistor is connected to the second logic level via its first terminal, grounded via its second terminal, and connected to the positive input of the operational amplifier via its sliding terminal.

6. The level conversion circuit according to claim 5, characterized in that, The logic level adjustment module further includes an inductor, which is connected to the second logic level with its first terminal, connected to the power supply voltage terminal of the drive circuit with its second terminal, and connected to the first terminal of the variable resistor with its second terminal. When the circuit is turned on, the inductor element filters out high-frequency noise.

7. The level conversion circuit according to any one of claims 2 to 5, characterized in that, The first signal terminal includes a first data terminal and a first clock terminal, and the second signal terminal includes a second data terminal and a second clock terminal.

8. The level conversion circuit according to any one of claims 1 to 6, characterized in that, Pull-up resistors are provided between the logic level and the first and second signal terminals of each module.

9. The level conversion circuit according to any one of claims 1 to 6, characterized in that, The first logic level ranges from 0.9V to 5V, the second logic level is 5V, and the third logic level ranges from 0.9V to 5V.

10. A signal testing device, characterized in that, It includes a tester and a device under test, and a level conversion circuit as described in any one of claims 1-9 connected between the tester and the device under test.

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