Leakage characteristics of the measurement signal path

Abstract

The present invention provides an exemplary method for measuring the leakage characteristics of a signal path. The exemplary method includes applying a current to the signal path; determining the parasitic capacitance of the signal path based on the rate of change of voltage on the signal path caused by the current; applying a voltage to the signal path for a time period; and after the time period, determining the leakage characteristics based on the parasitic capacitance and the rate of change of voltage on the signal path caused by the applied voltage.

Description

Technical Field

[0001] This specification describes an exemplary system configured to measure the leakage characteristics of a signal path. Background Technology

[0002] The test system is configured to test the operation of electronic devices and systems. Testing may include sending signals to the device through test channels and determining how the device responds to these signals based on its response. The response will determine whether the device passes the test.

[0003] Test channels have leakage characteristics, such as leakage current and leakage resistance. These leakage characteristics can affect testing. For example, some digital devices can operate deterministically when their signals are disconnected. The presence of leakage in such signals can force the device into an unknown state, thus adversely affecting testing. Therefore, equipment manufacturers may want to know the leakage specifications of a test system before using it.

[0004] Electronic devices can also leak. Device manufacturers may need to measure those leaks. Summary of the Invention

[0005] An exemplary method measures the leakage characteristics of a signal path. The exemplary method includes: applying a current to the signal path; determining the parasitic capacitance of the signal path based on the rate of change of voltage on the signal path caused by the current; applying a voltage to the signal path for a time period; and after the time period, determining the leakage characteristics based on the parasitic capacitance and the rate of change of voltage on the signal path caused by the applied voltage. The exemplary method may include one or more of the following features (alone or in combination).

[0006] Leakage characteristics can include leakage resistance. Leakage characteristics can include leakage current. Leakage characteristics can include both leakage resistance and leakage current.

[0007] Each rate of change of voltage can be determined by a testing instrument that measures the time at which different voltages occur along the signal path. The signal path may fluctuate after this time interval.

[0008] An exemplary method may include determining each rate of change of voltage along a signal path. The signal path may include a conduit within a test apparatus. The signal path may include an interface between the test apparatus and a device under test (DUT) being tested by the test apparatus. The signal path may include the DUT.

[0009] An exemplary system is configured to measure leakage characteristics of a signal path. The exemplary system includes: a voltage source connected to the signal path; a current source connected to the signal path; a circuit for measuring voltage on the signal path at time intervals; and a control system configured to (i) control the current source to apply current to the signal path, (ii) determine the parasitic capacitance of the signal path based on the rate of change of voltage on the signal path caused by the current and measured by the circuit, (iii) control the voltage source to apply voltage to the signal path for a time period, and (iv) after the time period, determine leakage characteristics based on the rate of change of voltage on the signal path caused by the applied voltage. The exemplary system may include one or more of the following features (alone or in combination).

[0010] Leakage characteristics can include leakage resistance. Leakage characteristics can include leakage current. Leakage characteristics can include both leakage resistance and leakage current.

[0011] The circuit can be configured to measure each rate of change of voltage on a signal path by measuring the voltage difference within a time interval. The circuit can also be configured to measure each rate of change of voltage on a signal path at different times between different voltage thresholds.

[0012] The voltage on the signal path may fluctuate after this time period. The signal path may include conduits within the test equipment. The signal path may include the interface between the test equipment and the device under test (DUT) being tested by the test equipment. The signal path may include the DUT.

[0013] Any two or more of the features described in this specification (including the content section) may be combined to form specific embodiments not specifically described in this specification.

[0014] At least a portion of the test systems and processes described in this specification can be configured or controlled by executing instructions stored on one or more non-transitory machine-readable storage media on one or more processing devices. Examples of non-transitory machine-readable storage media include read-only memory, optical disk drives, memory disk drives, and random access memory. At least a portion of the test systems and processes described in this specification can be configured or controlled using a computing system consisting of one or more processing devices and a memory storing instructions that can be executed by the one or more processing devices to perform various control operations.

[0015] The accompanying drawings and the following detailed description illustrate one or more specific embodiments. Other features and advantages will become apparent from the details, the drawings, and the claims. Attached Figure Description

[0016] Figure 1 This is a block diagram of the components of an exemplary test system on which the procedures described herein for measuring leakage characteristics can be used.

[0017] Figure 2 It is a flowchart illustrating the operations included in an exemplary process for measuring the leakage characteristics of an instrument test channel.

[0018] Figure 3 This is an exemplary circuit diagram showing the device under test electrically disconnected from the instrument's test channel.

[0019] Similar reference numerals in different figures indicate similar elements. Detailed Implementation

[0020] This document describes an exemplary system for measuring leakage through signal paths (e.g., test channels) of test instruments, interface circuitry, and / or the device under test (DUT). In an automated test system (ATE), leakage can be characterized by resistance and / or current on the test channel.

[0021] The system described in this paper utilizes the small parasitic capacitance inherent in all electrical signal paths, such as test channels, to measure the leakage characteristics of these signal paths. Generally, parasitic capacitance comprises the inherent capacitance present between components of electronic parts or circuits due to their relative proximity. Parasitic capacitance is generally undesirable, so test system designers strive to minimize its magnitude. For example, parasitic capacitance can be approximately 0.5 nanofarads (nF) or less. The small magnitude of parasitic capacitance in signal paths allows it to be used to measure small currents (such as currents at or below 10 nanoamps (10 nA)). In some examples, leakage currents of 1 nA or less can be measured. Moreover, the relative difference between leakage measurements can be measured at high resolution. For example, the difference between leakage measurements of 10 microamps (pA) or less can be determined.

[0022] The system described in this paper determines the parasitic capacitance of the signal path. This parasitic capacitance is then used to determine the leakage characteristics of the signal path (such as leakage current or leakage resistance). In this regard, the precise current application of the ATE channel and its ability to measure time intervals at specified voltages can be used to increase the accuracy of the applied current function. Using these resources, small leakage currents (e.g., approximately 10 nA or less) can be measured by performing the following operations.

[0023] Initially, a small current is injected into the signal path of interest. The current flowing into the capacitor of the signal path will cause a change in voltage across the signal path. The rate of change of this voltage across the signal path depends on the magnitude of the injected current and the parasitic capacitance of the signal path. This rate can be measured using the capabilities of a test instrument to measure the voltage at specified time intervals or to measure the time at a specified voltage level. Once the rate of voltage change is known, the parasitic capacitance of the signal path is determined. Next, the signal path is subjected to an initial voltage and then allowed to float. In this example, floating involves stopping the application of voltage or current to the signal path. In the floating state, the rate of change of voltage across the signal path is measured. Since leakage can be characterized as resistance rather than current, the leakage resistance is calculated using the parasitic capacitance and the voltage change. The leakage resistance can be defined by the leakage current measured at a specific voltage. Within a voltage range where the leakage resistance is linear, the leakage current at any voltage within that range can be determined using Ohm's law.

[0024] An exemplary test system may be configured to implement the aforementioned techniques for measuring leakage characteristics of a signal path. The exemplary test system may include: a voltage source connected to the signal path (e.g., a test channel); a current source connected to the signal path; and circuitry for measuring voltage on the signal path at time intervals or for measuring time at voltage levels. A control system (such as a computing system) is configured (e.g., programmed to): (i) control the current source to apply current to the signal path, (ii) determine the parasitic capacitance of the signal path based on the change in voltage on the signal path over time caused by the current and measured by the circuitry, (iii) control the voltage source to apply voltage to the signal path for a time period, and (iv) after that time period, determine leakage characteristics based on the change in voltage on the signal path over time and based on the parasitic capacitance.

[0025] Figure 1 Components of an exemplary ATE 10 are shown, which is configured to measure the leakage characteristics of a signal path. However, the techniques described herein are not limited to those... Figure 1 The test system shown is used in conjunction with, but is not limited to, general test systems. Instead, this technique can be used to measure leakage characteristics in any suitable technical context. For example, this technique can be used in any technical context where power dissipation is a concern in order to measure leakage current that affects power dissipation. Figure 1 In this context, dashed lines conceptually represent potential signal paths between system components.

[0026] ATE 10 includes a test head 11 and a host computing system 12. In this example, the host computing system is a control system. The host computing system may contain a computing system that includes one or more microprocessors or other suitable processing devices as described herein. A device interface board (DIB) 16, described below, is connected to the test head 11 and includes interfaces for one or more DUTs 21A to 21N on which the ATE performs tests.

[0027] exist Figure 1 In the example, DIB 16 is electrically and mechanically connected to test head 11. The DIB includes points 21, which may include pins, conductive traces, or other electrical and mechanical connection points to which the DUT can be connected. Test signals, response signals, and other signals are transmitted between the DUT and test equipment via test channels passing through the points. DIB 16 also includes connectors, conductive traces, and circuitry for routing signals between the test equipment, the DUT connected to point 21, and other circuitry.

[0028] The host computing system 12 communicates with the components of the test head to control the testing. For example, the host computing system 12 can download test suites to test instruments 13A to 13N in the test head. Test instruments are hardware devices that may include one or more processing devices and other circuitry. Test instruments 13A to 13N can run the test suites to test the DUT communicating with the test instruments. The host computing system 12 can also send instructions, test data, and / or other information to the test instruments in the test head, which can be used by the corresponding test instruments to perform appropriate tests on the DUT connected to the DIB via an interface. In some embodiments, this information can be sent via a computer or other type of network. In some embodiments, this information can be sent via a computer network (such as a local area network (LAN) or a wide area network (WAN)).

[0029] exist Figure 1In the example, ATE 10 includes multiple test instruments 13A to 13N, each of which can be appropriately configured to perform one or more tests and / or other functions. Although only three test instruments are depicted, the system can include any appropriate number of test instruments, including those located outside the test head 11. In some implementations, each test instrument can be configured to output a test signal to test the DUT based on data provided, for example, by a host computing system, and to receive a response signal from the DUT. Different test instruments can be configured to perform different tests and / or be configured to test different DUTs. The received signals may include response signals based on the test signals and / or signals originating from the DUT that are not prompted (e.g., not in response to) the test signals. In some implementations, an electrical conductor, such as copper wire, may be present between the DUT, DIB, and the test instrument interface through which test and response signals are transmitted.

[0030] In this example, one or more of the test instruments are VI (voltage-current) test instruments configured to apply a direct current (DC) voltage and a DC current to the test channel and receive a signal from the device based on the applied DC voltage and the applied DC current. However, other types of test instruments may be included in addition to VI test instruments. For example, test instruments configured to generate and detect high-speed digital signals may be used.

[0031] Signals can be sent to and received from the DUT via multiple test channels. In some examples, a test channel may include one or more physical transmission media through which signals are sent from the test instrument to the DUT and received from the DUT. The physical transmission medium may comprise a single electrical conductor or a combination of other types of media. The exemplary procedures described herein for measuring leakage characteristics are typically performed on an electrical conductor that is part of or constitutes a test channel.

[0032] Each test instrument has a corresponding interface (I / F) circuitry 16A to 16N for outputting signals to and receiving signals from the corresponding DUT. In some implementations, each interface circuitry may be implemented using devices such as field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), or other suitable hardware. The input and output circuitry of the test instrument may be located within the interface of each test instrument. In this respect, each test instrument may include input circuitry for receiving signals from one or more DUTs or other suitable signal sources. Each test instrument may also include output circuitry for outputting signals to a communication channel defined by the test instrument.

[0033] exist Figure 1In practice, test instruments 13A to 13N can be interconnected via base plate 42 or any other suitable electrical or mechanical mechanism. For example, test instruments 13A to 13N can be mechanically connected via an interface (e.g., insertion). Figure 1 The base plate 42 may include one or more transmission media through which signals travel. Figure 1 The transmission between components includes test instruments and test computer / host computing systems. In some implementations, the transmission medium may be or include one or more serial buses (such as a Peripheral Component Interconnect High Speed ​​(PCIe) bus, Ethernet cable, or a suitable type of copper or other conductive transmission medium).

[0034] In some examples, ATE 10 includes a connection interface 14 for connecting test instrument test channel 15 to DIB 16. Connection interface 14 may include connector 20 or other devices for routing signals between the test instrument and DIB 16. For example, the connection interface may include one or more circuit boards or other substrates on which such connectors are mounted. Conductors defining the test channel may be guided through the connection interface and the DIB.

[0035] Figure 2 At least some operations are illustrated in exemplary process 30, which is used to determine the leakage characteristics of a signal path (such as a test channel) using parasitic capacitance. Process 30 can be used to measure leakage of an ATE channel under high impedance conditions, but is not limited to its use in this context, as explained herein. Process 30 can be controlled using a computing system (such as host computing system 12). For example, the host computing system can control one or more test instruments to apply current and voltage to the test channel, as described below. The host computing system can perform the following calculations to determine leakage characteristics.

[0036] In this exemplary embodiment, process 30 includes applying (31) current to the signal path. In one example, an initial voltage is applied to the signal path. The applied voltage is switched to the applied current; that is, current is applied to the signal path. This current will cause the voltage on the signal path to rise or fall. Two voltage comparators may be connected to the signal path. These voltage comparators are, for example, programmed by the host computing system 12 to detect voltage thresholds (“voltage thresholds” are synonymous with “voltage levels”) within a range of rising or falling voltages on the signal path. The host computing system 12 determines the time taken for the voltage change on the signal path to cross these two voltage thresholds and stores it in computer memory. The voltage thresholds may be set based on the physical characteristics of the test system and the DUT. For example, the voltage operating range of the system may be known, and two voltage thresholds within that operating range may be selected. In another example, a voltage measurement circuit is connected to the signal path. Two or more voltage measurements are acquired at known time intervals. The host computing system 12 determines the voltage changes over these intervals and stores them in computer memory.

[0037] Process 30 includes determining (32) the parasitic capacitance of the signal path based on the rate of change of voltage on the signal path caused by the applied current. Since the applied current does not change within the voltage threshold range of the comparator, the parasitic capacitance C of the signal path can be determined as follows.

[0038] C = I prog *dt / dV,

[0039] Where dt is defined as (t compA -t compB ), where t compA and t compB It is the time that the programmed comparator voltage threshold is crossed. In the above text, dV is defined as (V... compA –V compB ), where V compA and V compB This is the voltage threshold to which the comparator is programmed. Alternatively, dV can be defined as the difference between two voltage measurements, and dt as the time interval between acquiring the two measurements. prog It is the current applied in the signal path.

[0040] Process 30 involves applying (33) a voltage to the signal path over a period of time. This period of time can be based on the length of the signal path under consideration and other factors. In the example, application involves applying an initial voltage to the signal path and then releasing the application condition (34), i.e., ending the applied voltage on the signal path. Leakage typically pulls the signal path toward electrical ground. The resulting rate of change of voltage on the signal path is measured. The leakage characteristics (35) are then determined based on the voltage change on the signal path and based on parasitic capacitance. In the example, to determine the voltage change, two comparators connected to the signal path are programmed to cross voltage thresholds that will be crossed as the voltage on the signal path changes. The time interval in which the comparator voltage thresholds are crossed is determined. In this example, the leakage characteristic is the leakage resistance. The formula for determining the leakage resistance R of the signal path is as follows.

[0041] R L =(t leakA -t leakB ) / (C*(ln(V leakA / V init )–ln(V leakB / V init ))),

[0042] Where V leakA and V leakB It is the voltage threshold to which the comparator is programmed, t leakA and t leakB It is the time during which the comparator voltage threshold is crossed, V init It is the initial voltage applied to the node, and "ln" is a function of the natural logarithm. In another example, the rate of voltage change is determined by taking voltage measurements at known time intervals. In this case, (t) leakA -t leakB ) is a known interval, while V leakA and V leakB These are two voltage measurements.

[0043] As mentioned earlier, a host computing system can perform computations and output R... L Stored in computer memory. The host computing system can determine the leakage current I at any given time using Ohm's law based on R and the voltage on the signal path at that time. L The host computer system can also transmit I L Stored in computer memory. L and I LThis can become the specification for the test system and can be used to determine which DUTs should be tested by the test system and which should not. As mentioned above, voltage thresholds can be set based on the physical characteristics of the test system and the DUTs. For example, the voltage operating range of the system can be known, and two voltage thresholds within that operating range can be selected. Determining the rate of voltage change may require at least two measurements. More than two measurements can be obtained to improve accuracy through averaging, or to determine leakage of signals with unknown leakage paths. For example, the commonly used voltage for electronic devices is 5 volts (V). Signals can have leakage paths leading to 5V or intermediate voltages or any voltage present within the test system. In some specific implementations, when the leakage path is unknown, at least three measurements can be used to determine the leakage of the signal path.

[0044] Leakage in the electrical signal path (e.g., R) L Or I L Leakage can occur anywhere along the electrical signal path. For example, leakage can occur on the signal path between the test instrument and the DUT, on the signal path between the test instrument and the DIB, on the signal path between the DIB and the DUT, within the DUT, within the DIB, and / or within the test instrument. Such leakage can be measured individually, for example, by disconnecting the path of interest, measuring a reference leakage, then reconnecting the path of interest and obtaining the measurement again. The difference between the two measurements is the leakage on the path of interest. For example, process 30 can be used to differentiate between measuring DIB leakage and DUT leakage. For example, refer to... Figure 3 To measure DUT leakage, a baseline measurement of leakage to the DUT is performed by removing the DUT 40 from instrument channel 41. Then, with the DUT (e.g., via switch 42) connected to the instrument channel, a leakage measurement is performed, and the baseline is subtracted to obtain the contribution of leakage from the DUT itself. For example, to measure DIB leakage, a baseline measurement of leakage to the DIB is performed by removing the DIB from the instrument channel (e.g., by disconnecting the DIB from the test head). Then, with the DIB connected to the test head, a leakage measurement is performed, and the baseline is subtracted from the measurement to obtain the contribution of leakage from the DIB itself. Other differential calculations of this type can be used to determine other leakage sources.

[0045] Figure 3 Comparators 42 and 43 are also shown, each of which can represent a connection relative to... Figure 2 One or more comparators for the described signal path.

[0046] Therefore, this document describes an exemplary test system configured to measure the leakage characteristics of a signal path. Examples of such test systems include an ATE (Automatic Test Equipment). Examples of leakage characteristics include leakage current and leakage resistance. Examples of signal paths include test instruments for testing the DUT (Digital Instrument Under Test), a DIB (Digital Instrument Block) for connecting the test instruments to the DUT via an interface, and the DUT itself or a combination of two or more of these. For example, a signal path may include one or more electrical conductors in the test instrument, the DIB, or the DUT.

[0047] All or part of the test systems and processes described in this specification, as well as various modifications thereof, may be configured or controlled at least in part by one or more computers (such as host computing system 12) using one or more computer programs tangibly embodied in one or more information carriers, such as in one or more non-transitory machine-readable storage media. The computer programs may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as standalone programs or as modules, parts, subroutines, or other units suitable for a computing environment. The computer programs may be deployed to execute on a single computer, at a single site, or distributed across multiple sites and interconnected via a network.

[0048] Actions associated with configuring or controlling the test system and process may be performed by one or more programmable processors executing one or more computer programs to control all or some of the trap-forming operations described previously. All or part of the test system and process may be configured or controlled by dedicated logic circuitry, such as FPGAs (Field-Programmable Gate Arrays) and / or ASICs (Application-Specific Integrated Circuits).

[0049] Processors suitable for executing computer programs include, for example, both general-purpose and special-purpose microprocessors, and any one or more processors in any kind of digital computer. Typically, a processor receives instructions and data from read-only memory or random access memory, or both. The components of a computer include one or more processors for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include (or be operatively coupled to receive data from or transfer data to, or both) one or more machine-readable storage media, such as mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks. Non-transitory machine-readable storage media suitable for embodying computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), and flash memory devices; magnetic disks such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM (Optical Disc Read-Only Memory) and DVD-ROM (Digital Universal Optical Disc Read-Only Memory).

[0050] The elements of the different embodiments described may be combined to form other embodiments not specifically described above. Elements may be omitted from the previously described system without generally adversely affecting its operation or the operation of the system. Furthermore, individual elements may be combined into one or more single elements to perform the functions described in this specification.

[0051] Other specific embodiments not specifically described in this specification are also within the scope of the following claims.

Claims

1. A method for measuring the leakage characteristics of a signal path, the method comprising: Apply current to the signal path; The parasitic capacitance of the signal path is determined based on the rate of change of the first voltage on the signal path caused by the current. A second voltage is applied to the signal path for a period of time; as well as After the stated time period, the leakage characteristics are determined based on the parasitic capacitance and the rate of change of the second voltage on the signal path, wherein the signal path includes a device under test (DUT), a test instrument for testing the DUT, a device interface board (DIB), or a combination of two or more of these, wherein the DUT or the DIB can be connected to and disconnected from the signal path, and wherein the rate of change of the second voltage is determined by using the voltage difference between different voltages on the signal path measured by the test instrument between connecting the DUT and / or the DIB to the signal path and disconnecting the DUT and / or the DIB from the signal path.

2. The method according to claim 1, wherein the leakage characteristic includes leakage resistance.

3. The method according to claim 1, wherein the leakage characteristic includes leakage current.

4. The method according to claim 1, wherein the rate of change of the first voltage is determined by a testing instrument that measures the time at different voltages along the signal path.

5. The method according to claim 1, wherein the rate of change of the first voltage is determined by a testing instrument, the testing instrument measuring the signal path at different times.

6. The method of claim 1, wherein the second voltage fluctuation on the signal path occurs after the time period.

7. The method according to claim 6, further comprising: Determine the rate of change of the first voltage and the second voltage on the signal path.

8. The method of claim 1, wherein the signal path comprises a conduit within the test device.

9. The method of claim 1, wherein the signal path includes an interface between the test device and the device under test being tested by the test device.

10. The method of claim 1, wherein the signal path includes the device under test.

11. An automated test equipment (ATE) system, the system comprising: A voltage source, which is connected to the signal path; A current source connected to the signal path; A circuit for measuring voltage on the signal path at time intervals; and A control system configured to (i) control the current source to apply current to the signal path, (ii) determine the parasitic capacitance of the signal path based on the rate of change of a first voltage on the signal path caused by the current and measured by the circuit, (iii) control the voltage source to apply a second voltage to the signal path for a time period, and (iv) after the time period, determine leakage characteristics based on the rate of change of the second voltage on the signal path, wherein the signal path includes a device under test (DUT), a test instrument for testing the DUT, a device interface board (DIB), or a combination of two or more of these, wherein the DUT or the DIB can be connected to and disconnected from the signal path, and wherein the rate of change of the second voltage is determined by using the voltage difference between different voltages on the signal path measured by the test instrument between connecting the DUT and / or the DIB to the signal path and disconnecting the DUT and / or the DIB from the signal path.

12. The automatic testing equipment system according to claim 11, wherein the leakage characteristic includes leakage resistance.

13. The automatic testing equipment system according to claim 11, wherein the leakage characteristic includes leakage current.

14. The automatic test equipment system of claim 11, wherein the circuit is configured to measure the rate of change of the first voltage on the signal path by measuring the voltage difference over a time interval.

15. The automatic test equipment system of claim 11, wherein the circuit is configured to measure the rate of change of the first voltage on the signal path at different times between different voltage thresholds.

16. The automatic test equipment system of claim 11, wherein the second voltage on the signal path floats after the time period.

17. The automatic testing equipment system of claim 16, wherein the leakage characteristic includes both leakage resistance and leakage current.

18. The automated test equipment system of claim 11, wherein the signal path includes a conduit within the test equipment.

19. The automatic test equipment system of claim 11, wherein the signal path includes an interface between the test equipment and the device under test being tested by the test equipment.

20. The automatic test equipment system according to claim 11, wherein the signal path includes the device under test.

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