CN210803660U - Weak current measuring device of ATE system - Google Patents
Weak current measuring device of ATE system Download PDFInfo
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- CN210803660U CN210803660U CN201921101199.1U CN201921101199U CN210803660U CN 210803660 U CN210803660 U CN 210803660U CN 201921101199 U CN201921101199 U CN 201921101199U CN 210803660 U CN210803660 U CN 210803660U
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Abstract
The utility model provides a weak current measuring device of ATE system, which comprises at least one group of I-V conversion circuit and V/I source; the I-V conversion circuit is used for current-voltage conversion, two measurement input ends of the I-V conversion circuit are connected with a tested loop in series, and the I-V conversion circuit is connected with the V/I source through a Kelvin circuit; the V/I source is connected with positive and negative power supply ends of the I-V conversion circuit through a Force H line and a Force L line of the Kelvin circuit to provide working voltage for the I-V conversion circuit, the output end of the I-V conversion circuit is connected through a Sense H line of the Kelvin circuit to measure the output voltage of the I-V conversion circuit, and the ground end of the I-V conversion circuit is connected through a Sense L line of the Kelvin circuit. The utility model discloses simple structure, small, low power dissipation can place the place very close to the device under test, therefore is difficult for receiving external disturbance, and the measuring accuracy is high.
Description
Technical Field
The invention relates to the technical field of integrated circuit testing, in particular to a weak current measuring device of an ATE system.
Background
In circuit testing, by being negativeThe load end series ammeter or parallel voltmeter can respectively realize the test of the current or voltage of the load end, as shown in figure 1, the current or voltage can be measured at V by connecting an ammeter in series in a tested loopBIASUnder the voltage, flows through a load RLThe current of (2). However, this test method is limited by the accuracy of current measurement, and cannot achieve high-accuracy measurement of weak current, and the interference in the line may have a large influence on the current to be tested.
When an integrated circuit automatic test system (ATE) tests various dc parameters, it provides various voltage/current source tables (hereinafter referred to as V/I sources) with different specifications, and the V/I sources may generally output voltage or current, and may also provide a function of measuring voltage or current. As shown in fig. 2, in order to accurately measure the voltage at the load end, the V/I source is usually designed in a Kelvin (Kelvin) connection mode, that is, four connections of Force High, Sense High, Force Low, and Sense Low are provided, wherein the Force port is used for supplying current, and the Sense port is used for measuring voltage. A certain voltage is allowed between the Force and Sense terminals of the V/I source because the device under test R is detected by setting a separate Sense line despite the presence of impedance in the line (as shown by the shaded portion on the Force line in FIG. 2)LAnd compensating for the voltage drop on the Force line so that the V/I source can still ensure the output/measurement of the device R to be testedLThe voltages across are accurate, which is a standard usage of V/I sources, namely Force H and Sense H and Force L and Sense L in the device R under testLIs shorted at the pin.
According to the principle, the V/I source in FIG. 2 can directly output VBIASVoltage to load RLTwo ends of the tube, and measuring the flow through the load RLCurrent of (I)L. However, this measurement usually guarantees only nA (10)-9A) Magnitude, since the V/I source provided by ATE system is usually a universal source meter, it needs larger output of voltage and current, measuring range, not to nA (10)-9A) Current measurement below grade is specially optimized; on the other hand, the weak current measuring capability is greatly influenced by the factors of large dynamic range of current, long connecting line, impedance in the line and the likeAnd (4) limiting. To accurately measure weak leakage currents below the nA level, a front-end circuit (e.g., various types of I-V conversion circuits) for small current measurement is usually added. In order to make the front-end circuit work normally, a power supply is required to be provided for the front-end circuit, and particularly, a group of positive and negative power supplies are generally provided under the condition that bidirectional current is measured; if the measurement terminal is not at zero potential (ground), a high voltage or floating set of power supplies is also required. In addition, a voltmeter is needed to measure the output voltage of the front-end circuit, so as to convert the measured current. However, the circuit is complex in design and high in cost, and cannot be widely applied to weak current testing of an ATE system.
Disclosure of Invention
In view of the above, the main objective of the present invention is to provide a weak current measurement apparatus and a measurement method for ATE system, the measurement apparatus has a simple structure, only needs a front-end circuit and a floating V/I source, and can measure weak leakage under non-zero bias voltage, and the precision can reach pA (10)-12A) Magnitude, and even higher. And because this measuring device simple structure, small, the low power dissipation can be placed to the place that is very close to the device under test, therefore is difficult for receiving external disturbance, and measurement accuracy is high.
The technical scheme adopted by the invention is that the weak current measuring device of the ATE system comprises at least one group of I-V conversion circuit and a V/I source;
the I-V conversion circuit is used for current-voltage conversion, two measurement input ends of the I-V conversion circuit are connected with a tested loop in series, and the I-V conversion circuit is connected with the V/I source through a Kelvin circuit;
the V/I source is connected with positive and negative power supply ends of the I-V conversion circuit through a Force H line and a Force L line of the Kelvin circuit to provide working voltage for the I-V conversion circuit, the output end of the I-V conversion circuit is connected through a Sense H line of the Kelvin circuit to measure the output voltage of the I-V conversion circuit, and the ground end of the I-V conversion circuit is connected through a Sense L line of the Kelvin circuit.
From the above, the present invention utilizes the characteristic of allowing certain voltage between the Force/Sense lines of the Kelvin circuit to pass through the V/I sourceThe front end is provided with an I-V conversion circuit, a constant current is output by a V/I source to drive the I-V conversion circuit to work, the current of the tested loop is measured, converted and amplified into voltage and fed back to the V/I source, and the load current on the tested loop can be tested by the V/I source according to the ratio of the measured voltage and the resistance on the I-V conversion circuit. The measuring precision of the invention can reach pA (10)-12A) The magnitude of the current is even higher, the structure of the measuring device is simple, the volume is small, the power consumption is low, and the measuring device can be placed in a place very close to a tested device, so that the measuring device is not easily interfered by the outside and has high measuring accuracy. When the V/I source used by the ATE system is a floating source, a plurality of sets of I-V conversion circuits can be used for matching with a plurality of paths of floating V/I sources, and weak currents of a plurality of loads can be measured simultaneously without mutual interference. Even if the ATE system uses a non-floating V/I source (common ground source), the invention can realize the dual functions of providing power supply for the front-end circuit and measuring the output voltage of the front-end circuit only by one non-floating V/I source.
Wherein the I-V conversion circuit includes:
the operational amplifier, two input ends of the operational amplifier are connected with the tested loop in series, a feedback resistor is connected between the output end and the inverting input end in series, and the non-inverting input end is grounded; the output end of the V/I source is connected with a Sense H line of the Kelvin circuit.
Therefore, the two input ends of the operational amplifier are connected in series to the tested loop, the current on the tested loop flows in from the non-inverting input end of the operational amplifier and flows out from the output end, and then flows through the tested device from the inverting input end of the operational amplifier through the feedback resistor, so that a closed current loop is formed. The voltage at the output end of the operational amplifier is also fed back to the V/I source, the voltage measured by the V/I source is the voltage obtained by multiplying the current by the feedback resistor, and the current value to be measured can be calculated.
Preferably, the positive power supply end of the operational amplifier is connected in parallel with a reverse voltage stabilizing diode and grounded; the negative power supply end is connected with a forward voltage stabilizing diode in parallel and is grounded.
The positive power supply end is connected with a voltage stabilizing diode in parallel to be grounded, and the cathode of the voltage stabilizing diode is connected with the positive power supply end and the anode of the voltage stabilizing diode is grounded; the negative power supply end is connected with a voltage stabilizing diode in parallel and is grounded, the cathode of the voltage stabilizing diode is grounded, the anode of the voltage stabilizing diode is connected with the negative power supply end, and the voltage stabilizing diode is used for establishing power supply voltage for the operational amplifier for the current output by the V/I source so as to enable the power supply voltage to meet the working rated voltage of the operational amplifier.
Preferably, the positive and negative power terminals of the operational amplifier are further connected in parallel with a filter capacitor and grounded, respectively.
Therefore, the power supply circuit can be filtered through the filter capacitor, and interference is eliminated.
Preferably, the I-V conversion circuit further includes:
the first resistor is connected between the output end of the operational amplifier and the feedback resistor in series;
and the second resistor is connected between the connection node of the feedback resistor and the first resistor in series and the ground terminal.
Preferably, the resistances of the first resistor and the second resistor are much smaller than the resistance of the feedback resistor.
Therefore, a T-shaped feedback resistance network is formed by the first resistor, the second resistor and the feedback resistor, so that the voltage on the feedback resistor is amplified, and the measurement sensitivity is improved.
Preferably, the output end of the operational amplifier is connected with a voltage amplifier in series and then is connected with the V/I source through a Sense H line of the Kelvin circuit.
Therefore, the output voltage can be amplified in equal proportion by serially connecting one-stage or multi-stage amplifying circuits, so that the measurement sensitivity is further improved.
Based on the weak current measuring device of the ATE system, the invention also provides a weak current measuring method of the ATE system, which comprises the following steps:
the V/I source is arranged to output a working current which supplies power to the I-V conversion circuit after being stabilized by the voltage stabilizing diode;
starting a V/I source to measure the output voltage of the I-V conversion circuit;
and calculating the weak current value of the measured target by using the voltage measured by the V/I source and the resistance of the I-V conversion circuit.
Therefore, the output current of the V/I source is set to meet the working voltage of the I-V conversion circuit after passing through the voltage stabilizing diode, the I-V conversion circuit converts the measured current and feeds the converted current back to the V/I source, and the load current of the tested loop of the ATE system can be calculated according to the voltage measured by the V/I source and the resistance of the I-V conversion circuit. When the V/I source used by the ATE system is a floating source, a plurality of sets of I-V conversion circuits can be used to be matched with a plurality of paths of floating V/I sources, and the method can be used for simultaneously measuring a plurality of load currents without mutual interference, thereby improving the measurement efficiency and the measurement precision.
Drawings
FIG. 1 is a circuit diagram of a load current measurement using an ammeter;
FIG. 2 is a circuit connection diagram of a V/I source using a Kelvin circuit to measure load current;
FIG. 3 is a schematic diagram of a weak current measurement device of an ATE system of the present invention;
FIG. 4 is a circuit diagram of a first embodiment of an I-V conversion circuit of the present invention;
FIG. 5 is a flow chart of a weak current measurement method of the ATE system of the present invention;
FIG. 6 is a circuit diagram of a second embodiment of an I-V conversion circuit of the present invention;
FIG. 7 is a circuit diagram of a third embodiment of an I-V conversion circuit of the present invention;
FIG. 8 is a schematic diagram of the present invention measuring multiple load currents.
Detailed Description
An embodiment of a weak current measuring apparatus of an ATE system according to the present invention will be described in detail with reference to fig. 3 to 8.
In a first embodiment, as shown in FIG. 3, the weak current measurement device of an ATE system provided by the invention comprises a V/I source and an I-V conversion circuit;
the I-V conversion circuit is used for current-voltage conversion, two measurement input ends I +, I-of the I-V conversion circuit are connected with a tested loop in series, the I-V conversion circuit is connected with the V/I source through a Kelvin circuit, the Kelvin circuit comprises a Force H line and a Sense H line which are connected with the positive pole of the V/I source, and a Force L line and a Sense L line which are connected with the negative pole of the V/I source, and the specific connection mode is as follows:
the positive electrode and the negative electrode of the V/I source are respectively connected with positive and negative power supply ends V + and V-of the I-V conversion circuit through a Force H line and a Force L line of the Kelvin circuit and used for outputting current to the I-V conversion circuit, and the positive electrode of the V/I source is also connected with an output end V of the I-V conversion circuit through a Sense H line of the Kelvin circuit0For measuring its output voltage V0The negative electrode of the V/I source is also connected with the grounding end GND of the I-V conversion circuit through a Sense L line of the Kelvin circuit;
in this embodiment, a non-standard usage of V/I source is provided, namely Force H/Sense H and Force L/Sense L are not under-test load RLThe pins are short-circuited, but by utilizing the characteristic that a certain voltage is allowed between Force/Sense lines, a certain current is output, the voltage established on the voltage regulators D1 and D2 by the output current is utilized to provide a group of positive and negative power supply voltages relative to GND (common end of D1 and D2) for the I-V conversion circuit, namely the operational amplifier A1, the current output by the V/I source is approximately equal to the sum of the working current of the operational amplifier A1 and the current flowing through D1(D2), and generally does not need to be large (for example, 8mA), as shown in figures 3 and 4, and the load current (leakage) I is ILFlows from the I + terminal, i.e. into GND of fig. 4, and flows from the output terminal of amplifier a1, through feedback resistor RF, and finally out the I-terminal, through load RLA closed current loop is formed, and the voltage Vo measured by the V/I source is IL*RFTherefore, IL＝Vo/RF；
V in the present exampleBIASOne voltage source and the other V/I source can be used as the voltage source, and the device can ensure R due to the virtual short characteristic of the operational amplifierLThe voltage across is set to VBIAS。
As shown in FIG. 4, in the present embodiment, the I-V converting circuit includes an operational amplifier A1, the non-inverting output terminal of the operational amplifier A1 is connected to the I + terminal of the tested loop, the inverting input terminal thereof is connected to the I-terminal of the tested loop, and the output terminal thereof is connected to the output terminal V of the I-V converting circuit0A feedback resistor R is also connected in series between the output end and the inverting input end of the operational amplifierFThe non-inverting input end of the transformer is grounded;
in order to ensure that the operational amplifier A1 obtains stable working voltage provided by a V/I source, the positive power end of the operational amplifier is used as the positive power end V + of the I-V conversion circuit and is connected in parallel with a reverse voltage stabilizing diode D1 and a capacitor C1 and then is grounded, the cathode of the voltage stabilizing diode D1 is connected with the positive power end V +, the anode is grounded, the negative power end V-is used as the negative power end V-of the I-V conversion circuit and is connected in parallel with a forward voltage stabilizing diode D2 and a capacitor C2 and then is grounded, the anode of the voltage stabilizing diode D2 is connected with the negative power end V-, and the cathode is grounded, wherein the V/I source establishes stable working voltage on the voltage stabilizing diodes D1 and D2 by utilizing output constant current and provides the stable working voltage for the operational amplifier A1 to normally work, and the capacitors C1 and C2 can filter the circuit and eliminate.
By using the circuit, the load R on the tested loop can be detectedLAs shown in fig. 5, the method specifically includes the following steps:
setting the V/I source to a Force I (constant current output) mode, enabling the V/I source to output a constant current, and enabling the constant current to supply power to the I-V conversion circuit after the constant current is stabilized by the voltage stabilizing diode;
starting output voltage V of V/I source to I-V conversion circuit0Carrying out measurement;
voltage measured by V/I source and resistance R of I-V conversion circuitFCalculating the load R on the tested loopLWeak leakage current ILNamely:
it should be noted that, in practical application, in order to ensure the accuracy of the measurement precision, the load R may not be connectedLIn the case of (1), the leakage current of the environment is measured once and then R is connectedLMeasuring the leakage current of the environment subtracted by the measured value to obtain the current flowing through RLOf (d) leakage value IL. It is also possible to use a known voltage VBIASAnd a load RLThe calibration of the measurement system, which is obvious to a person skilled in the art, is not described in detail here.
As shown in FIG. 6, in the second embodiment of the present invention, in order to improve the sensitivity of the I-V conversion circuit, resistors R1 and R2 are added on the basis of the I-V conversion circuit shown in FIG. 4, so as to be connected with the feedback resistor RFForming a T-shaped feedback resistance network, wherein the specific connection mode is as follows:
a resistor R1 is connected between the output end of the operational amplifier A1 and the feedback resistor RF in series, and the connection node of the feedback resistor RF and the resistor R1 is connected with the resistor R2 in series and then grounded;
in this embodiment, the improvement of the sensitivity of the I-V conversion circuit is to improve the output voltage V of the operational amplifier a10And the measured current ILThe ratio of (A) to (B) is necessarily passed through the feedback resistor R when the current flows from the I + port to the I-portFAnd in the feedback resistor RFA voltage is generated between the two ends, and a feedback resistor R is connected to the circuit through an operational amplifier A1 according to the circuit characteristicsFThe voltage generated at the two ends is amplified according to the proportion of the resistors R1 and R2, thereby increasing the output voltage V0And current ILThe sensitivity of the I-V conversion circuit is improved;
in this embodiment, the resistances of the resistors R1 and R2 are much smaller than the feedback resistor RFTo ensure that the current through resistors R1 and R2 is much larger than the current through feedback resistor RFCurrent (i.e. I)L) Due to ILVery small (e.g. 1nA), when R1, R2 take appropriate resistance value, the current flowing through R1, R2 reaches mA magnitude (e.g. when V isoAbout 0.5mA at 5V), a current of 1nA flows through R1 or R2, but is negligible compared with a current of 0.5 mA;
the output voltage V can be used0And a feedback resistor RFResistors R1 and R2 calculate load RLCurrent of (I)LNamely:
as shown in fig. 7, the present invention providesIn the third embodiment, the output voltage V can be obtained by connecting a voltage amplifier A2 in series with the output terminal of the operational amplifier A1 based on the I-V conversion circuit shown in FIG. 60After being amplified in equal proportion, the signals are fed back to a V/I source, so that the sensitivity of the I-V conversion circuit is further improved;
this principle and the above-mentioned raising of the output voltage V0And current ILThe principle of the ratio is the same, and is not described herein.
As shown in fig. 8, when the V/I source selected by the ATE system is a floating source, a plurality of sets of I-V conversion circuits can be used to simultaneously measure leakage weak currents of a plurality of loads in cooperation with a plurality of floating V/I sources without generating interference with each other;
the measurement principle in this embodiment is the same as that in the above embodiments, and is performed independently, which is not described herein again.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (7)
1. A weak current measuring device of an ATE system is characterized by comprising at least one group of I-V conversion circuits and a V/I source;
the I-V conversion circuit is used for current-voltage conversion, two measurement input ends of the I-V conversion circuit are connected with a tested loop in series, and the I-V conversion circuit is connected with the V/I source through a Kelvin circuit;
the V/I source is connected with positive and negative power supply ends of the I-V conversion circuit through a Force H line and a Force L line of the Kelvin circuit to provide working voltage for the I-V conversion circuit, the output end of the I-V conversion circuit is connected through a Sense H line of the Kelvin circuit to measure the output voltage of the I-V conversion circuit, and the ground end of the I-V conversion circuit is connected through a Sense L line of the Kelvin circuit.
2. The apparatus of claim 1, wherein the I-V conversion circuit comprises:
the operational amplifier, two input ends of the operational amplifier are connected with the tested loop in series, a feedback resistor is connected between the output end and the inverting input end in series, and the non-inverting input end is grounded; the output end of the V/I source is connected with a Sense H line of the Kelvin circuit.
3. The apparatus of claim 2, wherein the positive power terminal of the operational amplifier is connected in parallel with a reverse voltage regulator diode to ground; the negative power supply end is connected with a forward voltage stabilizing diode in parallel and is grounded.
4. The apparatus of claim 3, wherein the positive and negative power terminals of the operational amplifier are further connected in parallel with a filter capacitor to ground.
5. The apparatus of any of claims 2-4, wherein the I-V conversion circuit further comprises:
the first resistor is connected between the output end of the operational amplifier and the feedback resistor in series;
and the second resistor is connected between the connection node of the feedback resistor and the first resistor in series and the ground terminal.
6. The apparatus of any of claims 2-4, wherein the output of the operational amplifier is connected in series with a voltage amplifier and then connected to the V/I source through a Sense H line of the Kelvin circuit.
7. The apparatus of claim 5, wherein the output of the operational amplifier is connected in series with a voltage amplifier and then connected to the V/I source through a Sense H line of the Kelvin circuit.
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| CN201921101199.1U CN210803660U (en) | 2019-07-12 | 2019-07-12 | Weak current measuring device of ATE system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110275104A (en) * | 2019-07-12 | 2019-09-24 | 北京华峰测控技术股份有限公司 | A kind of weak current measuring device and measuring method of ATE system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110275104A (en) * | 2019-07-12 | 2019-09-24 | 北京华峰测控技术股份有限公司 | A kind of weak current measuring device and measuring method of ATE system |
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