Test circuit and platform for accurately testing cut-off state isolation of analog switch

Abstract

The invention discloses a test circuit and platform for accurately testing cut-off state isolation of an analog switch, and relates to the technical field of electronic circuits. The circuit of the test platform specifically comprises a sine generation circuit, a signal amplification circuit and a secondary filter circuit. The platform comprises a sine generation circuit, a DUT, a signal amplification circuit, a secondary filter circuit, an integrated circuit test machine and an oscilloscope. After the amplification filter circuit is added, the test accuracy can be improved, and a machine can be used for direct test; the design of a secondary band-pass filter is added, most noise signals are processed at a detection end, test waveforms are automatically generated through an integrated circuit test machine, different test channels are automatically controlled to be switched, and the signals can be automatically tested by the integrated circuit test machine through amplification and filtering; the test accuracy is improved, and the test efficiency is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a test circuit and a platform for accurately testing the cut-off state isolation of an analog switch. Background Art

[0002] The analog switch is a tristable circuit that can determine the state of the input and output terminals according to the level of the strobe terminal. When the strobe terminal is in the strobe state, the state of the output terminal depends on the state of the input terminal; when the strobe terminal is in the cut-off state, the output terminal is in a high-impedance state regardless of the input terminal level. Because analog switches have the characteristics of low power consumption, high speed, no mechanical contacts, small size and long service life. They play an extremely important role in the field of electronic equipment. Analog switches are often used in large-scale integrated circuits. Switches can be used to complete functions such as signal switching, control, and strobing. The main requirements for switch performance are high isolation, good frequency response characteristics, wide dynamic range, and small nonlinear distortion. An important indicator of analog switches is "cut-off isolation", which refers to the ratio of the input signal to the output signal amplitude when the analog switch is in the cut-off state.

[0003] In recent years, the data processing capabilities of chips have become stronger and stronger, the frequency has become higher and higher, and the accuracy requirements for isolation indicators have also increased accordingly. In the prior art, this indicator usually uses a waveform generator, a frequency meter, a voltage source and an oscilloscope to build a test circuit. When the analog switch is in the cut-off state, the signal at the output end is very weak, and direct testing cannot accurately test it, resulting in inaccurate results. In the chip detection industry, not only the accuracy of parameter indicator testing is extremely high, but also the detection speed is required. The chip detection industry usually uses a special integrated circuit test system to detect chip indicators. Usually, the resources of the integrated circuit test system are limited, and some parameter indicators require external other equipment to meet the test requirements. The isolation of the analog switch is such an indicator, which not only increases the complexity of the test equipment, but also reduces the test rate. Summary of the invention

[0004] The object of the present invention is to overcome one or more deficiencies of the prior art and to provide a test circuit and platform for accurately testing the cut-off state isolation of an analog switch.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A test circuit for accurately testing the cut-off state isolation of an analog switch, the circuit comprising: a sine generating circuit, a first-stage amplifying circuit, and a second-stage filtering circuit;

[0007] The first-stage amplifier circuit is a unidirectional signal amplifier circuit, and the output end of the analog switch of the first-stage amplifier circuit is connected to the unidirectional output end of the operational amplifier OPA1 of the first-stage amplifier circuit; the unidirectional output end of the operational amplifier OPA1 of the first-stage amplifier circuit is connected to the second end of the second resistor R2 and the first end of the third resistor R3; the reverse input end of the operational amplifier OPA1 of the first-stage amplifier circuit is connected to the first end of the second resistor R2 and the second end of the first resistor R1, and the first end of the first resistor R1 is grounded; the second end of the third resistor R3 is connected to the first end of the first capacitor C1, the first end of the second capacitor C2, and the first end of the fourth resistor R4; the first capacitor C1 The second end of the second capacitor C2 is connected to the first end of the fifth resistor R5 and the same-direction output end of the secondary filtering circuit amplifier OPA2, and the fifth resistor R5 is grounded; the same-direction output end of the secondary filtering circuit amplifier OPA2 is connected to the second end of the fourth resistor R4 and the second end of the seventh resistor R7, the reverse input end of the secondary filtering circuit amplifier OPA2 is connected to the first end of the sixth resistor R6 and the first end of the seventh resistor R7, and the second end of the sixth resistor R6 is grounded; the same-direction output end of the secondary filtering circuit amplifier OPA2 is connected to the integrated circuit test system through a pin, and the test system processes the signal.

[0008] A test platform for accurately testing the cut-off state isolation of an analog switch is provided. The platform uses a test circuit for accurately testing the cut-off state isolation of an analog switch. The platform includes: a sine generating circuit, a DUT, a primary amplifying circuit, a secondary filtering circuit, an integrated circuit testing system and an oscilloscope;

[0009] The integrated circuit test system also includes a test board, on which are arranged: a signal resource connection pin, a test base plate PCB, a test socket, and a test machine;

[0010] The sine generating circuit, the primary amplifying circuit, and the secondary filtering circuit are respectively connected and mounted on the test baseboard PCB; one end of the signal resource connecting pin is connected to the test baseboard PCB, and the other end is connected to different pins of the test machine;

[0011] The signal resource connection pin is used to lead the signal of the integrated circuit test system to the test board; the signal resource connection pin is connected to the resource output end of the DUT; the DUT and the oscilloscope are arranged on the test socket, the output end of the DUT is connected to the oscilloscope, and the oscilloscope is connected to the first-level amplification circuit and the second-level filtering circuit.

[0012] The beneficial effects of the present invention are:

[0013] (1) Use the integrated circuit test system to generate the required input sinusoidal signal, and amplify and filter the output signal for testing. This allows testing without the use of external equipment, reducing the use of equipment;

[0014] (2) The integrated circuit test system automatically generates test waveforms, automatically controls the switching of different test channels, and through amplification and filtering, the signal can be automatically tested using the integrated circuit test system, which can be better applied in the field of batch testing;

[0015] (3) When tested directly with an oscilloscope, the output signal is often composed of many noise signals superimposed on each other. Adding an amplifying and filtering circuit can not only improve the test accuracy but also enable direct testing using the system, thereby improving the prompt efficiency and being adaptable to batch testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a test link diagram of the present invention;

[0017] Figure 2 This is a schematic diagram of the test link of this embodiment;

[0018] Figure 3 It is a circuit diagram of the main parts of the primary amplification circuit and the secondary filtering circuit of the present invention;

[0019] Figure 4 This is a test flow chart of this embodiment. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0021] Example 1

[0022] A test circuit for accurately testing the cut-off state isolation of an analog switch, a test circuit for accurately testing the cut-off state isolation of an analog switch is provided, the circuit comprising: a sine generating circuit, a primary amplifying circuit, and a secondary filtering circuit (bandpass filtering circuit);

[0023] See also Figure 3The first-stage amplifier circuit is a unidirectional signal amplifier circuit, and the output end of the analog switch of the first-stage amplifier circuit is connected to the unidirectional end of the operational amplifier OPA1 of the first-stage amplifier circuit; the output end of the operational amplifier OPA1 of the first-stage amplifier circuit is connected to the second end of the second resistor R2 and the first end of the third resistor R3; the reverse input end of the operational amplifier OPA1 of the first-stage amplifier circuit is connected to the first end of the second resistor R2 and the second end of the first resistor R1, and the first end of the first resistor R1 is grounded; the second end of the third resistor R3 is connected to the first end of the first capacitor C1, the first end of the second capacitor C2, and the first end of the fourth resistor R4; the second end of the first capacitor C1 Grounded; the second end of the second capacitor C2 is connected to the first end of the fifth resistor R5 and the same-direction end of the operational amplifier OPA2 of the secondary filtering circuit, and the fifth resistor R5 is grounded; the output end of the operational amplifier OPA2 of the secondary filtering circuit is connected to the second end of the fourth resistor R4 and the second end of the seventh resistor R7, the reverse input end of the operational amplifier OPA2 of the secondary filtering circuit is connected to the first end of the sixth resistor R6 and the first end of the seventh resistor R7, and the second end of the sixth resistor R6 is grounded; the output end of the operational amplifier OPA2 of the secondary filtering circuit is connected to the integrated circuit test system through a pin, and the test system processes the signal through a specific interface function.

[0024] See also Figure 1-Figure 2 ,The test platform includes : a sine generating circuit, a device under test DUT, a primary amplifying circuit, a secondary filtering circuit, an integrated circuit testing system and an oscilloscope;

[0025] The test chain sequence is: sine generating circuit, device under test DUT, primary amplifying circuit, secondary filtering circuit and integrated circuit testing system.

[0026] The integrated circuit test system also includes a test board, on which are arranged: a signal resource connection pin, a test base plate PCB, and a test socket;

[0027] The sine generating circuit, the primary amplifying circuit, and the secondary filtering circuit are respectively connected and installed on the test base board PCB; one end of the signal resource connecting pin is connected to the integrated circuit test system, and the other end is connected to different pins of the test base board PCB;

[0028] The signal resource connection pin is used to lead the signal of the integrated circuit test system to the test board for direct use; the signal resource connection pin is connected to the resource output end of the DUT so that the integrated circuit test system can directly detect the output signal through the pin;

[0029] The device under test DUT is connected to the test socket and then connected to the oscilloscope. The oscilloscope is connected to the output end of the analog switch, and then connected to a first-stage amplification circuit and a second-stage filtering circuit.

[0030] The test base board PCB mainly provides a carrier for the primary amplification circuit, the filter circuit, the connection pins and the test socket;

[0031] The test board is connected to the integrated circuit test system resources;

[0032] The waveform generator is connected to the input end of the analog switch of the first-stage amplifier circuit, the frequency meter and the voltmeter are connected in parallel to the input end of the analog switch of the first-stage amplifier circuit, and the output end is connected to a load resistor. The CH1 channel of the oscilloscope is connected to the input end, and the CH2 channel is connected to the output end. The prior art tests this indicator by combining multiple devices, and the equipment is numerous and complex. In this embodiment, an integrated circuit test system is used to generate the required input sinusoidal signal, and the output signal is amplified and filtered for testing. It can be tested without using external equipment, reducing the use of equipment.

[0033] This embodiment uses the most basic co-directional signal amplification circuit and (active bandpass) secondary filtering circuit as examples. The test board is installed at the position of the integrated circuit test system and closely connected, and the chip to be tested is placed on the test socket of the test board. The waveform and amplitude of the analog switch input are set by the program. Assuming that the input sinusoidal signal is Vs, the isolated output signal is VD. Figure 3 The amplification factor of the first-stage amplifier circuit is A=R1 / (R1+R2)*Vin, where Vin is the input voltage. The amplification factor can be adjusted by changing the size of R1 and R2, and the amplification factor can be adjusted by flexibly changing the resistance value according to the output signal. The first-stage amplifier circuit amplifies the isolation signal and the noise signal of the input signal at the same time, and the amplified signal is coupled to the input end of the second-stage active bandpass filter at the back end.

[0034] There are two situations at the output of the analog switch. One is that the input-output isolation is good, and there are only low-level signals and noise signals at the output. In the case of poor isolation, there will be coupled signals and noise signals from the input at the output. According to the frequency of the input signal, R3 and R4 are changed to adjust the proportional coefficient to adjust the frequency band. The narrower the frequency band, the better the frequency selection characteristics. At this time, the signal output to the integrated circuit system is an amplified and frequency-selected signal. The small signal is amplified and the noise signal is filtered out. The test system can directly and accurately test, which improves the detection rate.

[0035] The sine generator circuit is generated by the integrated circuit test system through the STIL format pattern file. STIL (Standard Test Interface Language) language, the purpose of STIL is to provide a common language to represent the test code and waveform generated from the integrated circuit simulation. The data to be represented by the language is the waveform of the circuit under test, rather than the special hardware for the automatic test equipment (ATE). The pattern file is essentially a long string of binary codes. The file will use 1 and 0, P and N, which represent the high level or low level of the driver mapped to the hardware. The pattern file test combines binary symbols into a timing waveform that meets the IC design requirements and sends it to the IC and the IO state of the driver IC or compares the high and low states of a certain IO of the IC at a certain moment, so as to realize the functions of controlling the IC action or IC interactive data transmission. Pattern is like a waveform, with its speed, timing, state, delay time, etc. Bin file is a binary file, which is produced by STIL (Standard Test Interface Language) after compilation. When testing IC, the system generates the required input timing, waveform, etc. based on the imported Bin file.

[0036] The analog signal output end of the integrated circuit test system is directly connected to the input pin of the device under test (DUT). The device under test (DUT) consists of a test fixture, peripheral circuits, and an analog switch to be tested; the DUT to be tested is an analog switch that can be taken out and placed in a test fixture, and connected to various peripheral signals and detection ports through the test fixture.

[0037] The test fixture is designed and manufactured on a PCB test substrate. It is a test fixture used for electrical performance testing of analog switches, such as various packaged integrated circuit chips and electronic components, CPUs, module core boards, etc. It can fasten the pins of the analog switch to be tested to the peripheral signals. The peripheral circuits are a primary amplification circuit, a secondary filtering circuit, and a detection operation circuit.

[0038] The first-stage amplifier circuit is composed of a high-precision operational amplifier and its peripheral circuits; the first-stage amplifier circuit has a front end connected to the output end of the analog switch and a back end connected to a secondary filtering circuit. Its main function is to amplify the signal on the output side of the analog switch so that the back end can perform precision testing. The peripheral circuit of the first-stage amplifier circuit is composed of resistors and capacitors.

[0039] The secondary filter circuit is composed of an operational amplifier and its peripheral circuits; the peripheral circuits of the secondary filter circuit are composed of resistors and capacitors; the secondary filter circuit, the bandpass filter is a filter that only allows signals within a certain passband to pass through, while signals with frequencies lower than the lower limit of the passband and higher than the upper limit of the passband are attenuated or suppressed.

[0040] The front stage of the secondary filter circuit is connected to the first-stage amplifier circuit, and the rear stage is connected to the detection operation circuit. The main function is to filter the amplified signal at the output end, filter out the noise signal that is not at the same frequency as the input end, and make the output end test more accurate.

[0041] The integrated circuit test system is composed of analog resources, digital resources, power resources and control resources.

[0042] Analog resources include arbitrary waveform generation function. The sine signal at the input of the analog switch is generated by this resource. The analog resources can adjust the amplitude and frequency of the input sine signal arbitrarily according to the different analog switches, which greatly improves the flexibility.

[0043] Digital resources are resources required by digital chips, and this embodiment does not need to use this resource;

[0044] The power supply resource provides power for the analog switch, and the power supply voltage can be adjusted arbitrarily according to the different analog switches to meet the test requirements;

[0045] The control resource provides control signals for the analog resources, digital resources and power resources;

[0046] The oscilloscope converts electrical signals into visible images, and is used to observe waveform curves of various signal amplitudes changing over time, and to test various electrical quantities, voltages, currents, frequencies, phase differences, and amplitude modulations. The oscilloscope of this embodiment is a dual-trace oscilloscope.

[0047] Example 2

[0048] See also Figure 4 , is the test step flow chart of this platform. After starting the test platform, install the device to be tested, load the test program after installation, and perform the first test, the second test, the third test to the Nth test in sequence;

[0049] Among them, the first test is the sine generating circuit test, the second test is the first-stage amplification circuit test, and the third test is the second-stage filtering circuit test;

[0050] If the first test fails, the sine wave generating circuit will be tested. The problems to be tested include: power supply problem: unstable power supply or power supply voltage does not meet the requirements; component failure: failure or damage of components such as resistors, capacitors, transistors, etc.; line connection problem: poor connection or short circuit; parameter error: unreasonable parameter setting. The solutions to the problems include: checking the power supply to ensure that it is stable and meets the specified voltage, using a multimeter to check the normality of the components, replacing the faulty components, confirming that the circuit connection is correct and there is no looseness or short circuit, and resetting reasonable parameters.

[0051] If the second test fails, the first-stage amplifier circuit will be tested. The problems detected include: improper gain setting: the gain setting is too low or too high, resulting in output that does not meet the standard; incorrect bias voltage: the bias voltage setting is wrong, affecting the circuit operation; load mismatch: load impedance mismatch affects the amplification effect; signal source problem: the input signal source is unstable or the signal quality is poor. For the problems, the solutions include: adjusting the gain and bias settings to meet the design requirements, checking the input and output loads to ensure impedance matching, using a stable signal source, and ensuring that the input signal quality is good.

[0052] If the third test fails, the secondary filter circuit will be tested. The problems to be tested include: improper component selection: capacitors, inductors and other components do not meet the design requirements; function mismatch: improper selection of filter type (low-pass, high-pass, band-pass, etc.); frequency response problem: uneven frequency response, resulting in significant attenuation or gain outside the operating frequency band; power supply stray interference: stray signals in the power supply affect the filtering effect. For the problems, the solutions include: confirming that the parameters of the selected components meet the design requirements, re-evaluating the filter design, ensuring the selection of the appropriate filter type, adjusting component parameters, improving frequency response characteristics, and using filters to perform additional filtering on the power supply signal to reduce interference.

[0053] In each round of testing, there may be a variety of reasons that lead to test failure. Careful inspection of each link, timely adjustment and repair are the key to ensuring the normal function of the circuit. In each test, the next test can only be carried out after the test is passed, until the Nth test. Starting from the fourth test, the sine generation circuit, the first-level amplifier circuit or the second-level filter circuit can continue to be tested, and the circuits can continue to test and troubleshoot possible problems. After all the tests are passed, the test is terminated. If the test fails, the test will be repeated, which improves the rigor of the test.

[0054] The above embodiment uses an integrated circuit test system to generate the required input sinusoidal signal, and amplifies and filters the output signal for testing. It can be tested without using external equipment, reducing the use of equipment; the integrated circuit test system automatically generates test waveforms and automatically controls the switching of different test channels. At the same time, through amplification and filtering, the signal can be automatically tested using the integrated circuit test system. After adding the amplification and secondary filtering circuit, not only can the test accuracy be improved, but the system can also be used for direct testing, which can be better applied in the field of batch testing.

[0055] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A test circuit for accurately testing the cut-off state isolation of an analog switch, characterized in that: The circuit includes: a first-stage amplification circuit and a second-stage filtering circuit; The output end of the analog switch of the first-stage amplifier circuit is connected to the same-direction output end of the operational amplifier OPA1 of the first-stage amplifier circuit; the same-direction output end of the operational amplifier OPA1 of the first-stage amplifier circuit is connected to the second end of the second resistor R2 and the first end of the third resistor R3; the reverse input end of the operational amplifier OPA1 of the first-stage amplifier circuit is connected to the first end of the second resistor R2 and the second end of the first resistor R1, and the first end of the first resistor R1 is grounded; the second end of the third resistor R3 is connected to the first end of the first capacitor C1, the first end of the second capacitor C2, and the first end of the fourth resistor R4; the second end of the first capacitor C1 Grounded; the second end of the second capacitor C2 is connected to the first end of the fifth resistor R5 and the same-direction output end of the secondary filtering circuit amplifier OPA2, and the fifth resistor R5 is grounded; the same-direction output end of the secondary filtering circuit amplifier OPA2 is connected to the second end of the fourth resistor R4 and the second end of the seventh resistor R7, the reverse input end of the secondary filtering circuit amplifier OPA2 is connected to the first end of the sixth resistor R6 and the first end of the seventh resistor R7, and the second end of the sixth resistor R6 is grounded; the same-direction output end of the secondary filtering circuit amplifier OPA2 is connected to the integrated circuit test system through a pin.

2. A test platform for accurately testing the cut-off state isolation of an analog switch, the platform using the test circuit for accurately testing the cut-off state isolation of an analog switch according to claim 1, characterized in that: The platform includes: sine generating circuit, DUT, primary amplifying circuit, secondary filtering circuit, integrated circuit testing system and oscilloscope; The integrated circuit test system also includes a test board, on which are arranged: a signal resource connection pin, a test base plate PCB, a test socket, and a test machine; The sine generating circuit, the primary amplifying circuit, and the secondary filtering circuit are respectively connected and mounted on the test baseboard PCB; one end of the signal resource connecting pin is connected to the test baseboard PCB, and the other end is connected to different pins of the test machine; The signal resource connection pin is used to lead the signal of the integrated circuit test system to the test board; the signal resource connection pin is connected to the resource output end of the DUT; the DUT and the oscilloscope are arranged on the test socket, the output end of the DUT is connected to the oscilloscope, and the oscilloscope is connected to the first-level amplification circuit and the second-level filtering circuit.

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