Abstract:
A method for testing electronic devices involves receiving a stimulus signal for testing a device; changing an operating temperature of at least a component of an electrical filter while maintaining settings of the electrical filter, thereby altering the stimulus signal as the stimulus signal passes through the electrical filter, to create an altered stimulus signal; and outputting the altered stimulus signal.

Description:
BACKGROUND 
     A newly manufactured electronic device is tested by providing stimulus signals to the device and capturing its response. These measurements may be used to, for example, measure actual performance against expected performance. The electronic device may receive the stimulus signal to trigger the device under test (DUT). For example, the stimulus signal may include data that when received by the DUT, initiates a sequence of actions to be performed. The stimulus signal may be generated from a stimulus source that is electrically connected to a pin of a device through a printed circuit board known as text fixture or loadboard. 
     When testing a newly manufactured electronic device, the stimulus signal may experience loss of strength as it is transmitted through intermediate components from the testing apparatus to the DUT, e.g., wiring, an interface printed circuit board (PCB), etc. This loss often adds jitter to the stimulus signal. When the electronic device is tested, there are testing scenarios when an absence of jitter is preferred such as an ideal stimulus signal being used to measure the device operating at capacity. However, in other scenarios, the use of jitter is important to allow the testing to simulate actual scenarios. In a conventional method, a passive filter is used to equalize the loss or jitter that is created or to add a jitter to the stimulus signal. However, the passive nature of the filter restricts the testing to a specific set of conditions. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a method for electronic testing of devices. The method comprises receiving a stimulus signal for testing a device. The method comprises setting a filter by changing a performance characteristic of the filter while maintaining settings of the filter, thereby altering the stimulus signal to create an altered stimulus signal. The method comprises outputting the altered stimulus signal. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary embodiment of a system according to the present invention. 
         FIG. 2  shows an exemplary schematic of a buffer according to the present invention. 
         FIG. 3   a  shows an exemplary loss compensation graph. 
         FIG. 3   b  shows an exemplary jitter injection graph. 
         FIG. 4  shows an exemplary embodiment of a method according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments of the present invention provide a system and method for performing an electronic test on an electronic device. The exemplary embodiments of the present invention will be described with reference to the electronic test utilizing a buffer to control the stimulus signal. The buffer and control will be described in detail below. The following exemplary embodiments describe a testing device that measures a single electronic device. However, those skilled in the art will understand that the present invention may also apply to testing devices that are capable of measuring multiple electronic devices concurrently. 
     When the electronic device is used in actual scenarios, the device is likely to experience jitter being added to its receiver or transmitted signals timing and levels through various causes such as non ideal reference clock to the device under test, temperature variations, lossy signal paths for the signals, crosstalk from adjacent signals, etc. These causes may even occur in a testing environment because all signals experience a measure of loss as they are transmitted from the measurement equipment to the device under test. Since mechanical reasons dictate that there is always some distance between the measurement equipment and the device under test it is unlikely that the electronic device continuously functions in an environment that allows ideal performance. Thus, to simulate an ideal signal for testing purposes, an equalization approach is necessary to compensate for the loss in the signal. 
     Jitter is also an important aspect to testing an electronic device. Jitter is an abrupt and unwanted variation of one or more signal characteristics such as the timing interval between successive pulses, the amplitude of successive pulses, the frequency or phase of successive pulses, etc. Thus, simulating jitter in a testing environment is an integral part of the design of any electronic device. By simulating as many possible scenarios in a testing phase of an electronic device, performance measurements may assist in designing the electronic device. By thoroughly testing an electronic device through various jitter conditions, the capabilities of the electronic device may be fully understood, thereby determining if the electronic device operates in compliance with a standard and/or a manufacturer specification. On the other side, when performing a jitter measurement, it is important that no unwanted jitter is added to the signal being measured by external factors like the test fixture. Due to jitter being caused naturally through, for example, the resistive properties of the connection devices, an accurate measure of jitter may be impeded. Thus, to simulate a predetermined jitter strength, the loss in the signal requires amplification to reach the predetermined strength. 
       FIG. 1  shows an exemplary embodiment of a system  100  according to the present invention. The system  100  may be for performing a test on an electronic device. The test may be for various types of electronic devices and may, therefore, include the various tests performed for the different types of electronic device. For example, with memory devices, a transmit/receive signal may be used to determine if the memory device performs in compliance with at least one of the performance metrics defined in, for example, the PCI-Express specification, the IEEE standard, etc. The exemplary embodiments of the present invention incorporate the various tests for the various types of electronic devices. 
     The system  100  includes an automatic test equipment (ATE) device  102  which is electrically coupled to a tunable filter (TF)  106 . The TF  106  is electrically coupled to a device under test (DUT)  104 . The system  100  may further include a computer  108  (e.g., PC, laptop, tablet, etc.) which may be coupled to the DUT  104 , the TF  106 , and/or the ATE device  102 . The computer  108  (or any of the DUT  104 , the TF  106 , and/or the ATE device  102 ) may include a memory storing a set of instructions for implementing the electronic test. The computer  108  may include an output device, e.g., display screen, printer, etc., for outputting results of the electronic test. It should be noted that the use of a single ATE device  102  is only exemplary. Those skilled in the art will understand that multiple ATE devices may be electrically coupled directly to the DUT  104  or indirectly through the coupler  108 . These other ATE devices may further be connected to the computer  108 . For example, with frequency offset tests, one ATE device may include transmit and receive lines for data transmission/reception. Another ATE device may include a clock to time the different data transfers. 
     In the exemplary embodiment, the DUT  104  may be any electronic device (e.g., microprocessor, graphics processor, high speed memory device, etc.). In most cases, the DUT  104  purports to operate in accordance with a specification such as the PCI-Express specification, Hypertransport consortium, IEEE specification, etc. and the testing may be based on the specifications. The DUT  104  may implement, for example, a System-on-a-Chip (SoC) or a System-in-a-Package (SIP) architecture. The ATE device  102  may be SoCs which include a microprocessor, memory and a plurality of application specific integrated circuits (ASICs) implementing a test-per-pin architecture in which each pin of the DUT  102  may be tested independently. For example, the ATE device  102  may be for digitally testing channels. The ATE device  102  measures parametric performance measurements pertaining to the DUT  104 . This data may be transmitted to the computer  108  for storage and/or processing. 
     The TF  106  will be described with reference to  FIG. 2 .  FIG. 2  shows an exemplary schematic of the TF  106  of the system  100  of  FIG. 1 . In the exemplary embodiment, the TF  106  may include a resistor-capacitor (RC) filter. Thus, the TF  106  may include a capacitor  202  and a resistor  204 . The capacitor  202  and the resistor  204  may have settings pertaining to the respective component. For example, a manufacturer setting for the RC filter may be the capacitor  202  with a preset farad and the resistor with a preset ohm. In one exemplary embodiment, these manufacturer settings may be kept constant. However, in another exemplary embodiment, the manufacturer settings may be altered to adjust to the proper signal for testing. The TF  106  may further include a heating element  206 . The heating element  206  may provide or remove heat in accordance to the exemplary embodiment of the present invention. Those skilled in the art will understand that, in addition to the settings, the performance of the capacitor  202  and the resistor  204  may be dependent on temperature (i.e., performance characteristic). Thus, by controlling the heating element  206 , various testing conditions may be simulated such as compensating for loss of a signal or increasing jitter on a signal. That is, the performance characteristic of the TF  106  may be properly altered to correspond to the test to be performed on the DUT  104 . The use of the TF  106  in relation to controlling the testing conditions will be discussed in detail below with reference to  FIG. 4 . 
     As described above, there may be other intermediate components between the ATE  102  and the DUT  104 . For example, a PCB may be used to interface the ATE  102  to the DUT  104 . The PCB (or other intermediate component) may introduce the above described loss. The TF  106  may be located after these intermediate components to compensate for the loss. In one exemplary embodiment, the TF  106  may be implemented as a component on the PCB. In another exemplary embodiment, the TF  106  may be implemented as a separate component. 
     The use of a single heating element  206  is only exemplary. The TF  106  may include multiple heating elements for each of the components housed therein (e.g., a heating element for the resistor  204  and a separate heating element for the capacitor  202 ). It should also be noted that the TF  106  may be controlled through a variety of means. For example, the TF  106  may include a control input from the computer  108  and/or the ATE  102 . That is, the ATE  102  or the computer  108  may desire to set the heating element  206  of the TF  106  at a certain level. The ATE  102  or the computer  108  may output a control signal indicating that the heating element  206  should be set at the level. The level and the purpose of setting the level will be described in greater detail below. The TF  106  will receive the control signal and provide the heating element  206  with the requisite amount of power to achieve the desired heating level. It should be noted that other device or the TF  106  itself may also generate the control signal to control the heating level. 
     Those skilled in the art will understand that the power for the heating element  206  may be the control signal itself or may be from a separate power source. In the exemplary embodiment of the TF  106  being a component on the PCB, the heating element  206  may receive power from a power supply or source through the PCB. In another exemplary embodiment, the TF  106  may have a feedback mechanism such as a temperature detector (e.g., thermocoupler, RTD, etc.) that may indicate the temperature in the TF  106  so that the controlling device (e.g., ATE  102 , computer  108 ) may vary the control signal as needed. 
       FIG. 4  shows an exemplary embodiment of a method  400  according to the present invention. The method  400  describes a test for an electronic device that utilizes a tunable filter to adjust the stimulus signal according to predetermined conditions. The tunable filter provides a cost efficient (e.g., various stimulus signals with a common set of components) method to test an electronic device with an ideal signal and/or various degrees of jitter. The method  400  will be described with reference to the system  100  of  FIG. 1  and the TF  106  of  FIG. 2 . 
     In step  402 , conditions of the test to be performed on the DUT  104  is determined. As discussed above, the test may require a “pure” signal (i.e., ideal or unjittered) with no loss or a jittered signal with a specific loss. Therefore, prior to transmitting the signal to the DUT  104 , the appropriate measurements are calculated to create the corresponding signal. 
     In step  404 , a stimulus signal is activated. The stimulus signal may originate from the ATE device  102 . In addition, the stimulus signal is used to test the DUT  104  by activating a functionality (e.g., input a type of data related to the functionality) the DUT  104  purports to be able to execute in compliance with, for example, a standard and/or a manufacturer specification. 
     In step  406 , a determination is made whether to include an additional jitter into the stimulus signal. As discussed above, the stimulus signal experiences loss while being transmitted from the ATE  102  to the DUT  104 . Thus, to create the specific loss in the signal requires adding a difference in the amount of specific loss and the naturally occurring loss. 
     If it is determined in step  406  that the stimulus signal is not to include additional jitter, in step  408 , the TF  106  is set to compensate for any loss experienced by the stimulus signal while being transmitted. This scenario may arise, for example, when the test is to be conducted for the “pure” signal or a signal with less jitter than would occur based on the loss experienced while conducted through the circuit. That is, with a “pure” signal, the loss that is experienced is compensated by returning the stimulus signal to the conditions at the time the signal is transmitted from the ATE  102 . With a signal with less jitter that would occur based on the loss in the circuit, the loss that is experienced requires some correction to reach the target jitter strength. 
     The TF  106  may accomplish this compensation in a variety of manners. According to one exemplary embodiment of the present invention, temperature is used to compensate for the experienced loss. Those skilled in the art will understand that temperature has an effect on the capabilities of a resistor and capacitor. Thus, increasing or decreasing the temperature at which the resistor and capacitor operate alters the properties of the signal that is transmitted therethrough. 
     To compensate for loss in the signal, the heating element  206  may increase the temperature at which the TF  106  operates. The heating element  206  providing additional heat to the resistor  204  and/or the capacitor  202  may decrease the loss of the signal so that a target jitter is reached (e.g., less jitter than experienced on transmission) or the jitter that occurs is compensated (e.g., no jitter in the signal). 
     Those skilled in the art will understand that the capacitor  202  of the TF  106  may be controlled by temperature. That is, the magnitude of leakage current for the capacitor  202  may be controlled by the temperature, the type of dielectric, the capacitance rating, and/or the time of electrification prior to making the measurement. In particular with temperature, the insulation resistance properties of the capacitor  202  decreases with increased temperature. The increase in temperature causes an increase in the orbital velocity of the electrons therein, resulting in a higher flow of electrons through the capacitor  202 . Those skilled in the art will also understand that the resistor  204  of the TF  106  may be controlled by temperature. That is, the electrical resistance of a conductor may be dependent upon collisional processes within the resistor  204 . Therefore, the resistor  204  may be expected to increase its resistance with an increase in temperature since more collisions occur. Conversely, a decrease in temperature of either the capacitor  202  and/or the resistor  204  creates an opposite effect. 
     The use of the TF  106  and its constituent parts (e.g., capacitor  202 , resistor  204 ) may provide the necessary control to alter the stimulus signal from the ATE  104  appropriately. That is, through a common increase in temperature to both the capacitor  202  and the resistor  204 , the necessary compensation may be reached to create the proper signal. In another embodiment of the present invention, the heating element  206  may independently control the temperatures of the resistor  204  and the capacitor  202 . For example, increasing the temperature of the capacitor  202  and decreasing the temperature of the resistor  204  may create a signal that may further compensate for any loss of the signal. This situation may arise when, for example, the DUT  104  is used with an amplifier disposed between the ATE  102  and the DUT  104 . Therefore, to simulate this scenario, the independent control may be used. 
       FIG. 3   a  shows an exemplary loss compensation graph. The loss compensation graph illustrates an exemplary behavior for an RC circuit. For example, when the capacitor has a temperature of 40° C. and the resistor has a temperature of 30° C., a gain profile that is frequency dependent may be reached. In this case, the profile is intended to compensate the loss profile of a PCB test fixture that connects the ATE to the DUT. Other gain/frequency profiles might be reached depending on the specific profile of the DUT to ATE connection. It should be noted that each RC circuit is individual and may therefore be tuned based on the individual RC circuit response. That is, each TF  106  may have a specific gain response based on temperature (or other compensation factor). This response or performance may be programmed into the device generating the control signal for the TF  106 . In addition, a calibration procedure may be performed prior to use of a TF  106  in order to establish the response of the individual TF  106 . 
     If it is determined in step  406  that the stimulus signal is to include additional jitter, in step  410 , the TF  106  is set to add a corresponding jitter to the loss expected to be experienced by the stimulus signal while being transmitted. As discussed above, testing the DUT  104  in various jitter strengths allows a thorough comprehension of the capabilities of the DUT  104 . With a signal with more jitter than that naturally occurring, the loss that is experienced requires augmentation to reach the target jitter strength. 
     The TF  106  may also accomplish this augmentation in a variety of manners. According to one exemplary embodiment of the present invention, temperature is used to augment the experienced loss. As discussed above, those skilled in the art will understand that temperature has an effect on the capabilities of a resistor and capacitor. Accordingly, the decrease in temperature at which the resistor and capacitor operate provides the necessary augmentation to the signal. 
     To augment the loss in the signal, the heating element  206  may alter the temperature at which the TF  106  operates. The heating element  206  changes the heating to the resistor  204  and/or the capacitor  202  may increase the loss of the signal so that a target jitter is reached (e.g., more jitter than experienced on transmission). As discussed above, the change in temperature affects the capacitor  202  and/or the resistor  204  accordingly. 
       FIG. 3   b  shows an exemplary gain versus frequency graph of a filter that result in jitter being injected on the signal going through the filter. The jitter injection graph illustrates an exemplary behavior for an RC circuit. For example, when the capacitor has a temperature of 20° C. and the resistor has a temperature of 10° C., a specific gain versus frequency profile is generated. In this case, the profile has a low pass type filter behavior will reduce the bandwidth of the signal and in this way, inject jitter on the signal through a process known as inter-symbol interference in the case of a random data signal. Other profiles may also be reached depending on the parameters of the test (e.g., no jitter, slight jitter, etc.). It should again be noted that each RC circuit is individual and may therefore be tuned based on the individual RC circuit response. 
     In step  412 , the signal is relayed. As shown in the exemplary embodiment of system  100  of  FIG. 1 , the signal is relayed from the ATE  102  to the TF  106  to the DUT  104 . Thus, the signal may be altered according to the test conditions determined in step  402 . Once the signal is appropriately altered (e.g., steps  206 - 410 , the signal is prepared for relay so that the test may be performed in step  414 . 
     It should be noted that the method  400  may include additional steps. For example, the method  400  may be designed to compare the results of the test to a standard and/or a manufacturer specification. Thus, the method  400  may include a step where the standard and/or the manufacturer specification is loaded. Upon performing the test at step  414 , an alert may be displayed on the output device of the computer  108  indicating whether the DUT  104  passed or failed the electronic test. 
     It should also be noted that the stimulus signal being activated prior to altering the signal is only exemplary. The method  400  may activate the stimulus signal after setting the filter (e.g., step  408  or step  410 ). Thus, after determining the conditions of the test in step  402 , the method  400  may set the TF  106  according to the conditions. The stimulus signal may then be activated to be relayed. 
     Those skilled in the art will understand that the present invention may be applied to components of electronic devices as well. That is, the use of a finalized electronic device (i.e., complete manufacture) is only exemplary. For example, a finalized component of the electronic device may be the “DUT” where various constituent parts are the “components.” Thus, applying the system and method described above, the configuration of components may also be tested. 
     Those skilled in the art will also understand that the above described exemplary embodiments may be implemented in any number of manners, including, as a separate software module, as a combination of hardware and software, etc. For example, the method  200  may be a program containing lines of code that, when compiled, may be executed on a processor of the computer  108 . 
     The present invention allows the DUT  104  to be tested using a variety of stimulus signals from an ideal signal with no jitter to a signal experiencing a predetermined loss. Furthermore, the present invention also allows jitter to be controlled according to the tester&#39;s needs. Thus, the present invention provides a cost efficient system and method for testing an electronic device in various jitter conditions. The manufacturer may select a specific strength of jitter to be included in the stimulus signal. Therefore, the present invention eliminates the need for using various passive buffers that require swapping to attain testing conditions and allows for the variety of jitter strengths that are possible with the various passive buffers. 
     In one exemplary embodiment, the TF  106  is disposed on a printed circuit board (PCB) that is used to connect the ATE  102  to the DUT  104 . In such an embodiment, the ability to test the DUT  104  using the compensation signal is accomplished without altering the ATE  102  or the DUT  104  in any manner. Thus, an ATE  102  that does not include the ability to test using a compensation signal may be used to perform tests that require jitter or compensate for jitter without any modification to the ATE  102 . 
     It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.