JP5038454B2 - CURRENT MEASUREMENT DEVICE, TEST DEVICE, CURRENT MEASUREMENT METHOD, AND TEST METHOD - Google Patents

Description

  The present invention relates to a current measurement device, a test device, a current measurement method, and a test method. In particular, the present invention relates to a current measurement apparatus, a test apparatus, a current measurement method, and a test method for measuring a current received by an electronic device.

Conventionally, as a current measurement device that measures the current received by an electronic device, a large current measurement power supply circuit that is mainly used to measure the current consumed by the electronic device during operation, and the leakage current when the electronic device is stationary What is provided with the power circuit for small electric power measurement mainly used in order to measure is disclosed (refer patent documents 1 and 2).
Patent Document 1 Japanese Patent Laid-Open No. 2001-41997 Patent Document 2 Japanese Patent Laid-Open No. 2004-347421

  Due to the recent miniaturization of device manufacturing processes, the density and speed of electronic devices are increasing. As a result, more elements are switched at higher speeds, so that current consumption during operation of electronic devices is particularly large in CMOS circuits. Therefore, it is required to increase the capacity of the smoothing capacitor for stabilizing the power supply provided between the terminal of the electronic device under test in Patent Documents 1 and 2 and the ground. In addition, the number of gates mounted on an electronic device is increasing as the density of the electronic device is increased, and the leakage current tends to increase even in a stationary state.

  On the other hand, with the miniaturization of the device manufacturing process, the width of the insulating portion of the gate and the wiring has been reduced. For this reason, the leakage current caused by the insulation failure becomes smaller, and the detection of the insulation failure is becoming more difficult.

  On the other hand, according to the quiescent current measurement power supply circuit of Patent Document 1, when a large noise occurs in the voltage source of the reference voltage, the current supplied to the electronic device fluctuates greatly and a minute leak current is measured. It becomes difficult. Further, when the capacity of the smoothing capacitor is increased, the current to be supplied from the power supply circuit is increased according to the difference from the reference voltage. However, if the current supplied by the power supply circuit is increased according to the difference between the output voltage and the reference voltage, a large noise current is supplied and measured according to the noise voltage of the output voltage.

  Accordingly, an object of the present invention is to provide a current measuring device, a testing device, a current measuring method, and a testing method that can solve the above-described problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.

  According to a first aspect of the present invention, there is provided a current measuring apparatus for measuring a current received from an input terminal by an electronic device, wherein a reference supply voltage serving as a reference for a voltage supplied to the electronic device during current measurement is accumulated. One capacitor, a power switch connected to the first capacitor before current measurement to store the reference supply voltage, and disconnecting the power source from the first capacitor during current measurement; and during current measurement, A current supply unit that supplies current to the electronic device based on the reference supply voltage stored in the first capacitor and a terminal voltage of the input terminal; and a first current measurement unit that measures the supply current supplied to the electronic device A current measuring device is provided.

  The current supply unit amplifies a difference obtained by subtracting the terminal voltage from the reference supply voltage, and outputs a voltage added to the reference supply voltage; an output of the first difference amplifier; and an input of the first difference amplifier And a resistor that is connected to the terminal and supplies the supply current corresponding to the difference between the output voltage of the first differential amplifier and the terminal voltage to the input terminal.

  The first current measurement unit is configured to output a differential voltage obtained by subtracting the terminal voltage on the input terminal side of the resistor from the output voltage on the first differential amplifier side of the resistor, and based on the differential voltage And a measuring unit for measuring the supply current.

  The first current measurement unit further includes a voltage source that outputs a preset measurement reference voltage, and a second difference amplifier that outputs a differential amplification voltage obtained by amplifying the difference between the differential voltage and the measurement reference voltage. And the measurement unit may measure the supply current based on the differential amplification voltage.

  The first current measurement unit may further include a low-pass filter connected between the voltage source and the second differential amplifier.

  And a correction unit that corrects the reference supply voltage by adding a correction voltage corresponding to the differential voltage to the reference supply voltage, wherein the current supply unit is corrected by the correction unit during current measurement. A current based on a supply voltage and the terminal voltage may be supplied to the electronic device.

  The correction unit includes an adder that adds the correction voltage corresponding to the difference voltage to the reference supply voltage, and a second capacitor that accumulates an output voltage of the adder and supplies the output voltage to the first difference amplifier. May be.

  The correction unit is provided between the output of the adder and the second capacitor, and connects the second capacitor to the output of the adder for a predetermined period from the start of current measurement. And a second switch for disconnecting between the output of the adder and the second capacitor after elapse of the predetermined period.

  A power supply for supplying the reference supply voltage to the first capacitor and the input terminal before current measurement; a third switch for disconnecting the power supply from the first capacitor and the input terminal during current measurement; and during current measurement. By adding a predetermined offset voltage to the reference supply voltage stored in the first capacitor and supplying it to the current supply unit, the terminal voltage during current measurement is compared with the terminal voltage before current measurement. You may further provide the voltage adjustment part which makes it high.

  The third switch includes a wiring between the power source and the input terminal, a contact point of the wiring between the end of the first switch to which the first capacitor is not connected and the power source, and an output of the power source. A first transistor that is provided between the output terminal of the power supply and shuts off a current from the output terminal side of the power supply to the contact side when turned off between the output terminal of the power supply and the contact; You may have in series with the 2nd transistor which interrupts | blocks the electric current from the contact side to the output terminal side of the said power supply.

  Provided between the input terminal side terminal of the third switch and the fourth switch provided between the first differential amplifier, the input terminal side end of the resistor, and the input terminal A fifth current switch, a second current measurement unit for measuring a current supplied from the power source to the input terminal, an operating current test for measuring an operating current received by the electronic device during operation, and the electronic device A test control unit that controls a quiescent current test for measuring a quiescent current received during quiescence, wherein the test control unit turns on the third switch, the fourth switch, and the second switch in the operating current test. 5 is turned off, and the current supplied from the power source to the input terminal is measured as the operating current by the second current measuring unit. And the fourth switch and the fifth switch are turned on, and the current supplied to the electronic device based on the reference supply voltage and the terminal voltage stored in the first capacitor is changed to the first switch. The quiescent current may be measured by a current measurement unit.

  A measurement invalidity detection unit for detecting that the current measurement is invalid when the supply current measured by the first current measurement unit becomes larger than a preset threshold current during current measurement; Further, it may be provided.

  A power supply for supplying the reference supply voltage to the first capacitor and the input terminal before current measurement; and a third switch for disconnecting from the power supply, the first capacitor and the input terminal during current measurement, The measurement invalidity detection unit may turn on the third switch to supply current from the power source to the electronic device when detecting that the current measurement is invalid.

  According to the second aspect of the present invention, there is provided a test apparatus for testing an electronic device, the first capacitor for storing a reference supply voltage serving as a reference for the voltage supplied to the electronic device during the current measurement, and the current measurement. A power supply is previously connected to the first capacitor to store the reference supply voltage, and a first switch that disconnects the power supply from the first capacitor during current measurement, and a current storage to the first capacitor. A current supply unit that supplies a current based on the reference supply voltage and a terminal voltage of an input terminal of the electronic device to the electronic device, and a first current measurement unit that measures the supply current supplied to the electronic device. Providing test equipment.

  According to a third aspect of the present invention, there is provided a current measurement method for measuring a current received by an electronic device from an input terminal, wherein a reference supply voltage serving as a reference for a voltage supplied to the electronic device during the current measurement is a first reference voltage. A reference supply voltage accumulation stage for accumulating in a capacitor; and a power supply connected to the first capacitor before current measurement to store the reference supply voltage, and the power supply is disconnected from the first capacitor during current measurement. Controlling one switch; supplying a current to the electronic device based on the reference supply voltage stored in the first capacitor and a terminal voltage of the input terminal during current measurement; and the electronic device And a first current measurement step for measuring a supply current supplied to the current measurement method.

  According to a fourth aspect of the present invention, there is provided a test method for testing an electronic device, wherein a reference supply voltage serving as a reference for a voltage supplied to the electronic device during current measurement is stored in a first capacitor. A first step of controlling a first switch to connect the power supply to the first capacitor before current measurement to store the reference supply voltage and to disconnect the power supply from the first capacitor during current measurement; A switch control step, a current supply step of supplying a current based on the reference supply voltage stored in the first capacitor and a terminal voltage of an input terminal of the electronic device to the electronic device during a current measurement, and the electronic device And a first current measurement step for measuring a supply current supplied to the test method.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

1 shows a configuration of a current measuring device 10 according to an embodiment of the present invention. The structure of the power supply part 506 which concerns on embodiment of this invention is shown. The structure of the switch 152 and the switch 174 which concerns on embodiment of this invention is shown. The 1st example of operation of current measuring device 10 concerning an embodiment of the present invention is shown. The 2nd example of operation of current measuring device 10 concerning an embodiment of the present invention is shown. The 3rd example of operation of current measuring device 10 concerning an embodiment of the present invention is shown. The noise reduction effect of the current measurement apparatus 10 which concerns on embodiment of this invention is shown.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

  FIG. 1 shows a configuration of a current measuring apparatus 10 according to this embodiment together with an electronic device 20. The current measuring apparatus 10 measures, for example, a current received from an input terminal such as a power supply terminal by an electronic device 20 that is a device under test (DUT) such as an LSI. The current measuring apparatus 10 is, for example, a test apparatus that tests the electronic device 20, and performs an operating current test that measures current consumed by the electronic device 20 during operation and a quiescent current test that measures leakage current during quiescence. The current measurement apparatus 10 according to the present embodiment can reduce noise of the current supplied to the electronic device 20 in the quiescent current test, and can measure the leak current with higher accuracy.

  The current measuring apparatus 10 includes a test control unit 90, a power supply unit 506, a pattern generation unit 502, a signal input unit 504, and a determination unit 508. The test control unit 90 controls the power supply unit 506, the pattern generation unit 502, the signal input unit 504, and the determination unit 508. The power supply unit 506 is a power supply device that supplies power supply current to the electronic device 20. The power supply unit 506 measures the magnitude of the power supply current supplied to the electronic device 20 in the operating current test and the quiescent current test of the electronic device 20, and notifies the determination unit 508 of the measurement result. The pattern generation unit 502 executes a test program sequence based on an instruction from the test control unit 90 and generates a test pattern to be supplied to the electronic device 20.

  The signal input unit 504 receives and shapes the test pattern and generates a test signal to be supplied to the electronic device 20. That is, for example, the signal input unit 504 generates a signal waveform specified at a timing specified by the test pattern. Then, the signal input unit 504 supplies a test signal to the electronic device 20. The determination unit 508 determines pass / fail of the electronic device 20 based on a signal output from the electronic device 20 according to the test signal. In addition, the determination unit 508 determines the quality of the electronic device 20 based on the magnitude of the power supply current supplied to the electronic device 20. In the above, the current measuring device 10 may function as a current measuring device according to the present invention.

  FIG. 2 shows the configuration of the power supply unit 506 according to this embodiment together with the electronic device 20 and the test control unit 90. The power supply unit 506 includes a current measurement unit 30, a current measurement unit 40, and a capacitor 50. The current measurement unit 30 is mainly used for a quiescent current test of the electronic device 20, supplies a small current to the electronic device 20 compared with the current measurement unit 40, and measures the magnitude of the supplied supply current to measure the current. The current received by device 20 is measured. The current measuring unit 40 is mainly used for an operating current test of the electronic device 20, supplies a current larger than the current measuring unit 30 to the electronic device 20 during a function test of the electronic device 20, and measures the magnitude of the supplied current. Thus, the current received by the electronic device 20 is measured. In the capacitor 50, when the current consumed by the electronic device 20 temporarily increases, the terminal voltage of the input terminal 25 varies depending on the delay until the current measurement unit 30 and the current measurement unit 40 increase the current supply amount. It is a smoothing capacitor to prevent

  The current measuring unit 30 is an example of a current measuring apparatus according to the present invention, and supplies current to the electronic device 20 and measures current received from the input terminal by the electronic device 20. The current measurement unit 30 according to the present embodiment controls the terminal voltage of the electronic device 20 based on the voltage accumulated in the capacitor 100 instead of generating a voltage serving as a reference for the terminal voltage of the input terminal 25 by a power supply or the like. To do. Thereby, the current measuring unit 30 can supply a stable current with a small noise current to the electronic device 20.

  The current measurement unit 30 includes a switch control unit 35, a voltage follower 172, a capacitor 100, a switch 102, a resistor 104, a current supply unit 110, a current measurement unit 120, a correction unit 140, and a voltage adjustment unit 160. A measurement invalidity detection unit 180, a switch 170, and a switch 174. The switch control unit 35 controls on / off of each switch (102, 141, 144, 148, 163, 166, 170, 174, etc.) in the current measurement unit 30. In addition, the switch control unit 35 according to the present embodiment further controls on / off of the switch 152 in the current measurement unit 40.

  The voltage follower 172 has a positive input connected to the input terminal 25 via the switch 170, a negative input connected to the output of the voltage follower 172, and changes the output voltage according to the input voltage and the output voltage, thereby changing the input voltage. Output a stabilized output voltage. The output end of the voltage follower 172 is connected to the switch 102 and the resistor 113 in the current supply unit 110.

  The capacitor 100 stores a reference supply voltage that is a reference for a voltage supplied to the electronic device 20 during current measurement. The capacitor 100 is connected between the input of the reference supply voltage to the correction unit 140 and the ground. The switch 102 is connected between the reference supply voltage output side end of the capacitor 100 and the power supply 150. The switch 102 is turned on by the switch control unit 35 before the current measurement by the current measurement unit 30, and the power supply 150 in the current measurement unit 40 is connected to the capacitor 100 to accumulate the reference supply voltage. The switch 102 is turned off by the switch control unit 35 during current measurement by the current measurement unit 30 to disconnect the power supply 150 from the capacitor 100. Thus, the capacitor 100 can input the accumulated voltage to the correction unit 140 with little discharge during current measurement. The resistor 104 is connected between the end of the switch 102 on the capacitor 100 side and the end of the capacitor 100 on the reference supply voltage output side.

  The current supply unit 110 inputs the reference supply voltage of the capacitor 100 through the correction unit 140 and inputs the terminal voltage of the input terminal 25 through the switch 170 and the voltage follower 172 during the current measurement by the current measurement unit 30. . The current supply unit 110 supplies the electronic device 20 with a current based on the reference supply voltage accumulated in the capacitor 100 and the terminal voltage of the input terminal 25 during the current measurement by the current measurement unit 30.

  The current supply unit 110 includes a differential amplifier 112, a resistor 113, a resistor 114, a voltage follower 116, a resistor 118, and a capacitor 119. The differential amplifier 112 is an example of a first differential amplifier according to the present invention, and amplifies the difference obtained by subtracting the terminal voltage from the reference supply voltage input via the correction unit 140, and uses the voltage added to the reference supply voltage. Output. More specifically, the differential amplifier 112, when the terminal voltage is lower than the reference supply voltage, adds a positive voltage obtained by amplifying the difference obtained by subtracting the terminal voltage from the reference supply voltage to the reference supply voltage. Output. When the terminal voltage is higher than the reference supply voltage, a voltage obtained by adding a negative voltage obtained by amplifying the difference obtained by subtracting the terminal voltage from the reference supply voltage to the reference supply voltage is output. Resistor 113 and resistor 114 determine the amplification factor of differential amplifier 112. More specifically, when the resistance value of the resistor 113 is Ri and the resistance value of the resistor 114 is Rf, the amplification factor G is Rf / Ri. The amplification factor is preferably 1 or more in order to reduce the amount of decrease in the terminal voltage of the input terminal 25.

  The voltage follower 116 is a difference calculator having a positive input connected to the output of the differential amplifier 112 and a negative input connected to the output of the voltage follower 116. The voltage follower 116 outputs an output voltage in which the input voltage is stabilized by changing the output voltage according to the input voltage and the output voltage. The resistor 118 is connected between the output of the differential amplifier 112 and the input terminal 25, and supplies a supply current corresponding to the difference between the output voltage of the differential amplifier 112 and the terminal voltage of the input terminal 25 to the input terminal 25. The capacitor 119 is connected between the end of the resistor 118 on the input terminal 25 side and the ground, and stabilizes the current supplied to the input terminal 25 via the resistor 118.

  The current measurement unit 120 is an example of a first current measurement unit according to the present invention, and measures the supply current supplied to the electronic device 20 by the current supply unit 110. The current measurement unit 120 includes a difference calculator 122, a measurement unit 124, a voltage source 126, a low pass filter 128, a difference amplifier 130, and a measurement unit 132. The difference calculator 122 is connected between the voltage follower 116 and the input terminal 25, and outputs a difference voltage obtained by subtracting the terminal voltage on the input terminal 25 side of the resistor 118 from the output voltage on the difference amplifier 112 side of the resistor 118. The measuring unit 124 measures the supply current based on the differential voltage. More specifically, when the resistance value of the resistor 118 is Rm and the differential voltage is Vim, the measurement unit 124 measures the differential voltage Vim by an AD converter or the like, and divides by the resistance value Rm, thereby supplying the supply current Iddq (= Vim / Rm).

  The voltage source 126, the differential amplifier 130, the measurement unit 132, and the low-pass filter 128 are provided to measure the supply current Iddq to the electronic device 20 with higher accuracy than the measurement unit 124. The voltage source 126 includes, for example, a DA converter that converts a digital voltage set value set by the test control unit 90 into an analog voltage, and outputs a measurement reference voltage set in advance by the test control unit 90. The differential amplifier 130 outputs a differential amplified voltage obtained by amplifying the difference between the differential voltage output from the differential calculator 122 and the measurement reference voltage output from the voltage source 126. The measuring unit 132 measures the supply current based on the differential amplification voltage output from the differential amplifier 130. The low-pass filter 128 is connected between the voltage source 126 and the differential amplifier 130, and stabilizes the measurement reference voltage output from the voltage source 126.

For example, when the theoretical value of the current Iddq received by the electronic device 20 at rest is 20 mA, when the supply current Iddq is measured in units of 1 μA using the measurement unit 124, the measurement unit 124 determines the voltage of the difference calculator 122. It is necessary to measure as a digital value of 15 bits or more. This is because 20 mA / 1 μA = 20,000 and 2 ¹⁴ <20,000 <2 ¹⁵ .

  Therefore, the current measurement device 10 outputs the measurement reference voltage Vref from the voltage source 126 in advance when measuring the supply current with high accuracy. The current measuring apparatus 10 supplies a voltage source that is substantially the same as the voltage output by the difference calculator 122 corresponding to the current Iddq that is slightly smaller than the theoretical value so that the Vref is smaller than the voltage output by the difference calculator 122. 126 is set.

  The difference amplifier 130 outputs a voltage obtained by amplifying the difference voltage Vim2 (= Vim1-Vref) between the output voltage Vim1 of the difference calculator 122 and the measurement reference voltage Vref by N times. The measuring unit 132 measures the voltage output from the differential amplifier 130, thereby accurately measuring the supply current Iddq using an AD converter having a smaller number of bits compared to the case of directly measuring the output voltage of the difference calculator 122. can do.

For example, if the theoretical value of the current Iddq received by the electronic device 20 at rest is 20 mA and the difference between the actual current values is ± 1 mA, if Vref = 19 mA, the difference amplifier 130 has a difference current ΔIddq = A differential amplification voltage corresponding to 0 to 2 mA is output. Therefore, when the supply current Iddq is measured in units of 1 μA using the measurement unit 132, the measurement unit 132 may measure the voltage of the differential amplifier 130 as a 12-bit digital value. This is because 2 mA / 1 μA = 2,000 and 2 ¹¹ <2,000 <2 ¹² .

  When the difference ΔIdddq of the supply current due to the individual electronic device 20 is 10% of the theoretical value of the supply current Iddq, the voltage source 126 sets the measurement reference voltage Vref with a resolution in voltage units corresponding to 10% of Iddq. It only needs to be able to output. The value obtained by multiplying the setting resolution of the voltage source 126 by the measurement resolution of the measurement unit 132 should be equal to or greater than the value obtained by dividing Iddq by a measurement unit (for example, 1 μA).

  Further, when the plurality of electronic devices 20 are measured to obtain the supply current difference ΔIdddq, the error of the measurement reference voltage Vref by the voltage source 126 is canceled out, so that an accurate ΔIdddq is obtained.

  Since the measurement reference voltage Vref output from the voltage source 126 does not change during the measurement period, the low-pass filter 128 is provided between the voltage source 126 and the difference amplifier 130, so that the difference between the difference amplifier 130 and the measurement unit 132 is obtained. An accurate current value can be obtained in a shorter measurement period compared to providing a low-pass filter to reduce noise.

  The correction unit 140 corrects the reference supply voltage by adding a correction voltage corresponding to the differential voltage output from the difference calculator 122 to the reference supply voltage of the capacitor 100. Thereby, when the current Iddq received by the electronic device 20 depends on the terminal voltage Vdd of the electronic device 20, the terminal voltage of the electronic device 20 can be corrected and a more accurate current Iddq can be measured. In the present embodiment, an operation mode of the current measuring device 10 that corrects the reference supply voltage according to the differential voltage is referred to as a voltage correction mode. The correction unit 140 adjusts the reference supply voltage supplied to the differential amplifier 112 in the current supply unit 110 according to the voltage output from the voltage adjustment unit 160.

  Correction unit 140 includes a switch 141, a resistor 142, a capacitor 143, a switch 144, an adder 145, a capacitor 146, a resistor 147, and a switch 148. The switch 141 is connected between the output of the difference calculator 122 and the input of the adder 145. The switch 141 is turned on by the switch control unit 35 when supplying a correction voltage based on the differential voltage to the reference supply voltage during current measurement, and supplies the differential voltage of the differential calculator 122 to the adder 145. On the other hand, when the correction is not performed, the switch control unit 35 turns off during the current measurement. The resistor 142 is connected between the switch 141 and the adder 145.

  The capacitor 143 is connected between the input of the adder 145 and the ground, stabilizes the differential voltage of the differential calculator 122 and supplies the same to the adder 145 in the same manner as the capacitor 100. More specifically, when performing the above correction, the switch control unit 35 turns on the switch 141 and turns off the switch 144 during the quiescent current test, and accumulates the differential voltage of the differential calculator 122 in the capacitor 143. Then, the switch control unit 35 turns off the switch 141 before the current measurement unit 120 measures the supply current to the electronic device 20. Thereby, the capacitor 100 can supply the accumulated differential voltage to the adder 145.

  The switch 144 is connected between the end of the switch 141 on the adder 145 side and the ground. The resistor 142 is turned off by the switch control unit 35 when performing the above correction. On the other hand, when the correction is not performed, it is turned on by the switch control unit 35, the input of the adder 145 is set to 0V, and the reference supply voltage is not corrected.

In the case of performing the above correction, the adder 145 amplifies the differential voltage output from the difference calculator 122 and accumulated in the capacitor 143 by a predetermined amplification factor and adds it to the reference supply voltage, thereby correcting the corrected reference A supply voltage is supplied to the differential amplifier 112. Thereby, the current supply unit 110 can supply a current based on the reference supply voltage corrected by the correction unit 140 and the terminal voltage of the input terminal 25 to the electronic device 20 during the current measurement.
The adder 145 adjusts the reference supply voltage by further adding the voltage output from the voltage adjustment unit 160 to the reference supply voltage.

  The capacitor 146 is connected between the wiring between the adder 145 and the difference amplifier 112 and the ground, accumulates the output voltage of the adder 145, and supplies the voltage accumulated during the current measurement to the difference amplifier 112. The switch 148 is provided between the output of the adder 145 and the capacitor 146 on the wiring between the adder 145 and the difference amplifier 112. The switch 148 is controlled by the switch control unit 35 and connects the capacitor 146 to the output of the adder 145 to store the output voltage of the adder 145 for a predetermined period from the start of current measurement by the quiescent current test. Then, after the lapse of the predetermined period, the output of the adder 145 and the capacitor 146 are disconnected, and the voltage stored in the capacitor 146 is supplied to the differential amplifier 112. Resistor 147 is connected between switch 148 and capacitor 146.

  Note that the current measuring apparatus 10 that does not perform the above-described correction or the like may be configured without the correction unit 140, and the capacitor 100 may be directly connected to the differential amplifier 112.

  The voltage adjustment unit 160 is connected to the input of the adder 145. Then, the voltage adjustment unit 160 adds the offset voltage preset by the test control unit 90 to the reference supply voltage accumulated in the capacitor 100 during current measurement, and supplies it to the current supply unit 110 via the correction unit 140. . The voltage adjustment unit 160 according to the present embodiment sets the offset voltage to 0 V before the current measurement and sets the offset voltage to a positive value during the current measurement, thereby changing the terminal voltage during the current measurement to the terminal voltage before the current measurement. Higher than Thus, the voltage adjustment unit 160 can set the terminal voltage during the logic setting period (setup period) inside the electronic device 20 before the quiescent current test to a lower value than during the quiescent current test. In addition, it is possible to prevent the electronic device 20 from generating heat and measuring a high leakage current. In the present embodiment, the operation mode of the current measuring device 10 that increases the terminal voltage during current measurement compared to before current measurement is referred to as a voltage variable mode.

  Voltage adjustment unit 160 includes a voltage source 162, a switch 163, a resistor 164, a capacitor 165, and a switch 166. The voltage source 162 is a DA converter, for example, and outputs an offset voltage corresponding to the setting from the test control unit 90. The switch 163 is provided on the wiring between the voltage source 162 and the adder 145, and is controlled by the switch control unit 35. The voltage source 162 is provided between the wiring between the switch 163 and the adder 145 and the ground, and is controlled by the switch control unit 35.

  The capacitor 165 is connected between the wiring between the switch 163 and the adder 145 and the ground, accumulates an offset voltage while the switch 163 is on, and adds the offset voltage even when the switch 163 is off. Continue to supply to the vessel 145. The resistor 164 is provided between the switch 163 and the capacitor 165 in the wiring between the switch 163 and the adder 145.

  In the voltage adjustment unit 160 described above, the switch 163 is turned off and the switch 166 is turned on before the quiescent current test. Thereby, the adder 145 is supplied with a voltage of 0V. Thereby, before the quiescent current test, the adder 145 can output to the current supply unit 110 without adding the offset voltage to the reference supply voltage. On the other hand, during the quiescent current test, the switch 163 is turned on and the switch 166 is turned off. As a result, the adder 145 can add the offset voltage to the reference supply voltage and output it to the current supply unit 110. Further, the switch 163 may be turned off after a predetermined period has elapsed since the start of the quiescent current test. Thereby, the capacitor 165 can stably supply the accumulated offset voltage to the adder 145.

  The measurement invalidity detection unit 180 inputs the differential voltage output from the difference calculator 122, and when the supply current measured by the current measurement unit 120 becomes larger than a preset threshold current during current measurement. , Detecting that the current measurement is invalid. The measurement invalidity detection unit 180 includes a voltage source 182, a difference calculator 184, and an invalid recording unit 186. The voltage source 182 outputs a voltage corresponding to the threshold current. The difference calculator 184 subtracts the difference voltage output from the difference calculator 122 according to the supply current from the voltage of the voltage source 182. When the output voltage of the difference calculator 184 becomes negative during current measurement, the invalid recording unit 186 records that the current measurement is invalid and notifies the test control unit 90 of the fact.

  The switch 170 is provided between the wiring between the switch 152 and the input terminal 25 in the current measuring unit 40 and the differential amplifier 112. More specifically, the switch 170 is provided between a terminal on the input terminal 25 side of the switch 152 existing in the current measuring unit 40 and a voltage follower 172 provided between the differential amplifier 112. The switch 174 is provided between the input terminal 25 and the end of the resistor 118 on the input terminal 25 side.

  The current measurement unit 40 includes a power source 150, a switch 152, a capacitor 60, a resistor 70, and a current measurement unit 155. The power supply 150 supplies current to the electronic device 20 during the operating current test. The power supply 150 supplies a reference supply voltage to the capacitor 100 and the input terminal 25 before current measurement in the quiescent current test. Switch 152 disconnects power supply 150 from capacitor 100 and input terminal 25 during quiescent current measurement. The capacitor 60 is connected between the wiring between the power supply 150 and the switch 152 and the ground, and prevents the terminal voltage of the input terminal 25 from being lowered when the current Idd greatly fluctuates due to the operation of the electronic device 20. The resistor 70 is provided on the wiring between the capacitor 60 and the switch 152, and an electric current corresponding to the difference between the output voltage of the power supply 150 and the terminal voltage of the input terminal 25 is electronic while the switch 152 is on. Flow to device 20.

  The current measurement unit 155 is an example of a second current measurement unit according to the present invention, and inputs a voltage across the resistor 70 and measures a current supplied from the power source 150 to the input terminal 25. That is, for example, the current measurement unit 155 performs the same operation as the current measurement unit 120 that measures the current based on the voltage across the resistor 118, during the operating current test of the electronic device 20 based on the potential difference across the resistor 70. The current supplied to the device 20 is measured.

  In the current measuring apparatus 10 described above, the test control unit 90 controls the operating current test and the quiescent current test of the electronic device 20 as described below. In the operating current test for measuring the operating current received during operation of the electronic device 20, the test control unit 90 controls the switch control unit 35 to turn on the switch 152, turn off the switch 170 and the switch 174, and the power supply 150 is turned on. The current supplied to the input terminal 25 is measured by the current measuring unit 155 as an operating current.

  On the other hand, in the quiescent current test that measures the quiescent current received by the electronic device 20 during quiescence, the test control unit 90 controls the switch control unit 35 during the set-up period of the quiescent current test, and switches 152, 170, and 174 The switch 102 and the switch 148 are turned on, and the reference supply voltage supplied from the power source 150 is accumulated in the capacitor 100 and the capacitor 146 and supplied to the electronic device 20. When the current measurement is started, the test control unit 90 controls the switch control unit 35 to turn off the switch 152, turn on the switch 170 and the switch 174, turn off the switch 102, and store the reference stored in the capacitor 100. The current measurement unit 120 measures the current supplied to the electronic device 20 based on the supply voltage and the terminal voltage as a quiescent current. Note that the test control unit 90 turns off the switch 148 after the elapse of a predetermined period from the start of the current measurement, and applies the electronic device 20 to the electronic device 20 based on the corrected reference supply voltage and terminal voltage accumulated in the capacitor 146. The supplied current may be measured as a quiescent current.

  According to the current measuring apparatus 10 described above, a current based on the difference between the reference supply voltage and the terminal voltage accumulated in the capacitor 100 and / or the capacitor 146 can be supplied to the electronic device 20, and noise current is reduced. be able to. In addition, the current measurement unit 120 can accurately measure the supply current to the electronic device 20. Further, the reference supply voltage can be corrected according to the current supplied to the electronic device 20, and a stable voltage can be supplied to the electronic device 20 in which the leakage current changes according to the voltage. Moreover, the temperature rise of the electronic device 20 can be prevented by lowering the terminal voltage during the setup period of the quiescent current test as compared with that during the current measurement.

  FIG. 3 shows a configuration of the switch 152 according to the present embodiment. The switch 152 is provided between the wiring between the power source 150 and the input terminal 25, the end of the switch 102 to which the capacitor 100 is not connected and the wiring between the power source 150 and the output terminal of the power source 150. It is done. The switch 152 includes a transistor 200 and a transistor 210 in series between both ends. The transistor 200 is provided between the output terminal of the power source 150 and the contact point, and cuts off the current from the output terminal side of the power source 150 to the contact side when the transistor 200 is turned off. On the other hand, a reverse current can flow to some extent even when it is turned off. The transistor 210 is provided between the output terminal of the power supply 150 and the above contact, and cuts off the current from the contact side to the output terminal side of the power supply 150 when turned off. On the other hand, a reverse current can flow to some extent even when it is turned off.

  According to the switch 152 described above, it is possible to prevent the current from flowing between the current measuring unit 40 during the quiescent current test in both directions, and to accurately measure the supply current to the electronic device 20. it can. Note that the switch 174 may have the same configuration as the switch 152. In this case, it is possible to prevent the current from flowing between the current measuring unit 30 during the operating current test in both directions.

  FIG. 4 shows a first operation example of the current measuring apparatus 10 according to the present embodiment. The first operation example shows a high-speed mode operation in which a test is performed at high speed without correcting the reference supply voltage according to the supply current supplied to the electronic device 20.

  The quiescent current test is divided into a measurement preparation period (setup period) T1 for preparing to measure the supply current of the electronic device 20, a current measurement period T2 for measuring the supply current Iddq when the electronic device 20 is stationary, and a restoration period T3. It is done.

  In the measurement preparation period T1, the test control unit 90 turns on the switch 170 (S1a), the switch 174 (S1b), the switch 152 (S2a), the switch 102 (S2b), and the switch 148 (S5). Thereby, the voltage output from the current measuring unit 40 is supplied to the electronic device 20 and is stored in the capacitor 100. In this operation example, since the reference supply voltage is not corrected, the switch 141 (S4) is turned off and the switch 144 is turned on during the quiescent current test. In this operation example, since the voltage variable mode operation is not performed, the switch 163 (S3) is turned off and the switch 166 is turned on during the quiescent current test. As a result, the offset voltage Voff output from the voltage adjustment unit 160 is 0V.

  In the measurement preparation period T1, the current measurement apparatus 10 supplies a test signal sequence to the electronic device 20 so as to be in a stationary state that is a target of a stationary current test. Along with this operation, the current Idd consumed by the electronic device 20 changes. On the other hand, the current measuring unit 40 supplies a current Is corresponding to the current consumed by the electronic device 20 to the input terminal 25, and stabilizes the terminal voltage Vdd.

  When the setup of the electronic device 20 is completed, the current measurement period T2 is started. At the start of the current measurement period T2, the switch 152 (S2a), the switch 102 (S2b), and the switch 148 (S5) are disconnected. The current supply unit 110 can supply a current based on the difference between the reference supply voltage stored in the capacitor 100 and the capacitor 146 and the terminal voltage of the input terminal 25 to the input terminal 25.

  The measurement unit 124 and / or the measurement unit 132 in the current measurement unit 120 disconnects a predetermined timing within the current measurement period T2, that is, for example, the switch 152 (S2a), the switch 102 (S2b), and the switch 148 (S5). The voltage output from the internal AD converter is measured after a predetermined period has elapsed. Based on the measured voltage, the current value of the quiescent current supplied to the electronic device 20 is acquired.

  Then, in the restoration period T3, the switch 152 (S2a), the switch 102 (S2b), and the switch 148 (S5) are turned on again, and the current supply from the current measuring unit 40 to the electronic device 20 is resumed.

  In the above, when the current supply from the current measuring unit 30 is started, the terminal voltage of the input terminal 25 can be decreased by the voltage ΔV1 as compared with the reference supply voltage accumulated in the capacitor 100. Here, depending on the type of the electronic device 20, there may be a function of automatically resetting and initializing the inside when the power supply voltage is lowered. In such a test of the electronic device 20, when a large current flows during the current measurement period T2, the terminal voltage Vdd falls below the threshold voltage that is a reference for resetting and is initialized. In this case, for example, the current Iddq received by the electronic device 20 decreases, and a defective product is erroneously determined as a pass, or measurement is performed in a state different from the internal state of the electronic device 20 to be tested. Problem arises.

Therefore, the measurement invalidity detection unit 180 determines that the current measurement is invalid when the supply current measured by the current measurement unit 120 becomes larger than a preset threshold current during the current measurement period T2. Is detected. When the measurement invalidity detection unit 180 detects that the current measurement is invalid, the measurement invalidity detection unit 180 turns on the switch 152 (S2a) to supply current from the power supply 150 to the electronic device 20. Here, the measurement invalidity detection unit 180 compares the measurement voltage Vim output from the difference calculator 122 with the threshold voltage output from the voltage source 182 so that the supply current is greater than the threshold current. Is detected. The operation when the invalidity of the current measurement is detected is indicated by a broken line in FIG.
Thus, current can be supplied from the current measuring unit 40 to the electronic device 20 before the input terminal 25 falls below the threshold voltage that is a reference for reset, and the electronic device 20 can be prevented from being reset. it can.

  FIG. 5 shows an operation in the voltage correction mode as a second operation example of the current measuring apparatus 10 according to the present embodiment.

First, the principle of the voltage correction mode is shown.
When the current received by the electronic device 20 depends on the terminal voltage, when the terminal voltage Vdd changes, the quiescent current measured by the measurement unit 124 or the measurement unit 132 also changes.

  More specifically, the ideal terminal voltage stored in the capacitor 100 is Vs, the actual terminal voltage is Vdd, and among the quiescent current of the electronic device 20, the current independent of the terminal voltage Vdd is Idd1 and the terminal voltage Vdd. When the dependent current is Idd2, and the equivalent resistance of the circuit depending on the terminal voltage Vdd in the electronic device 20 is RL, the following equation is established.

(Formula 1) (Va − Vb) = Vs · (1 + G) − Vdd · (1 + G)

  However, Va is the voltage at the end of the resistor 118 on the differential amplifier 112 side, and Vb is the voltage at the end of the resistor 118 on the input terminal 25 side. G is the amplification factor of the differential amplifier 112, and is obtained from the resistance value Rf of the resistor 114 and the resistance value Ri of the resistor 113 by G = Rf / Ri.

  Here, the left side of Formula 1 can be transformed as Formula 2 below.

(Formula 2) (Va − Vb) = Rm · (Idd1 + Idd2) = Rm · (Idd1 + Vdd / RL)

  When the left side of Equation 1 is transformed by Equation 2 and solved for Vdd, the following equation is obtained.

(Formula 3) Vdd = Vs · (1 + G) · X1 − Idd1 · Rm · X1
X1 = RL / (Rm + RL ・ (1 + G))

  Here, when the current Idd received by the electronic device 20 is completely voltage-dependent, for example, when Vs = 1V, Idd1 = 0A, Idd2 = 10 mA, Rm = 200Ω, and G = 50, RL is 100Ω (= 1V / 10 mA). ) Substituting these into Equation 3, it can be seen that Vdd = 0.962V and a voltage drop of 38 mV occurs. Therefore, when the terminal voltage is an ideal value of 1 V, the measured current is 10 mA (= Vs / RL), but in reality, the measured current is 9.62 mA (= Vdd / RL).

  Therefore, in the voltage correction mode, correction is performed by adding a correction voltage corresponding to the differential voltage output from the difference calculator 122 to the reference supply voltage. More specifically, the adder 145 corrects the difference voltage of the difference calculator 122 by 1 / N2 and adds it to the reference supply voltage Vs. The setting method of N2 is shown below.

  When the correction is added to Equation 1, the following equation is obtained.

(Formula 4) (Va − Vb) = (Vs + (Vs−Vb) / N2) ・ (1 + G) − Vdd ・ (1 + G)

  Solving Equation 4 for Vdd yields:

(Formula 5) Vdd = Vs − (Va − Vb) ・ (1 − (1 + G) / N2)) / (1 + G)

  If N2 = G + 1 in Equation 5, (Va−Vb), that is, Vdd = Vs regardless of the values of Idd1 and Idd2. Therefore, the adder 145 corrects the terminal voltage by amplifying the difference voltage output from the difference calculator 122 by an amplification factor obtained by adding 1 to the amplification factor of the difference amplifier 112 and adding the reference voltage to the reference supply voltage. can do. In this case, the correction unit 140 performs correction to increase the reference supply voltage when a larger differential voltage is detected, and performs correction to decrease the reference supply voltage when a smaller differential voltage is detected. It becomes.

  Next, the operation in the voltage correction mode in which the above correction is performed will be described with a focus on differences from the operation example of FIG. First, in the measurement preparation period T1, the current measurement device 10 performs setup in the same manner as in the high speed mode of FIG.

  When the setup of the electronic device 20 is completed, the current measurement period T2 is started. At the start of the current measurement period T2, the switch 152 (S2a) and the switch 102 (S2b) are disconnected. Thereby, the capacitor 100 can supply the accumulated reference supply voltage to the adder 145. Further, the switch 141 (S4) is turned on and the switch 144 is turned off, and the differential voltage is accumulated in the capacitor 143. The switch 148 (S5) is kept on.

  Next, since the differential voltage is accumulated in the capacitor 143 after a predetermined period has elapsed, the switch 141 (S4) is turned off. Thereby, the capacitor 143 can supply the accumulated differential voltage to the adder 145.

  Next, after the switch 141 (S4) is turned off, the adder 145 corrects a voltage obtained by adding a correction voltage based on the differential voltage stored in the capacitor 143 to the reference supply voltage stored in the capacitor 100. Output as the later reference supply voltage. Since the corrected reference supply voltage is accumulated in the capacitor 146 after a predetermined period has elapsed, the switch 148 (S5) is turned off. Thereby, the capacitor 146 can supply the accumulated reference supply voltage after correction to the differential amplifier 112.

  The current supply unit 110 supplies a current based on the difference between the corrected reference supply voltage stored in the capacitor 146 and the terminal voltage of the input terminal 25 to the input terminal 25. Thereby, the current supply unit 110 can substantially match the terminal voltage of the input terminal 25 with the ideal voltage Vs accumulated in the capacitor 100.

  Thereafter, similarly to the operation example of FIG. 4, the current value is measured, and the operation in the restoration period T3 is performed. Also in this operation example, measurement invalidity detection by the measurement invalidity detection unit 180 is performed.

  According to the voltage correction mode described above, the quiescent current can be measured in a state where the terminal voltage of the input terminal 25 is close to the ideal value by adding a correction voltage corresponding to the differential voltage to the reference supply voltage. Thereby, the quiescent current of the electronic device 20 whose consumption current changes depending on the terminal voltage can be appropriately measured.

  In the voltage correction mode, the voltage is stored in the capacitor 143 and the capacitor 146, so that the current measurement period T2 can be longer than that in the high-speed mode. In such a current measuring apparatus 10, it is preferable to use the high-speed mode and the voltage correction mode properly depending on the characteristics of the electronic device 20.

  The capacitances of the capacitor 100, the capacitor 146, the capacitor 143, and the capacitor 165 are the maximum off-time of the switch 102, the switch 148, the switch 141, and the switch 163 corresponding to each, and the capacitors in the state where these switches are turned off May be determined based on the leakage current from and the allowable voltage fluctuation. As an example, the capacity of the capacitor 100 is 1 nA × 1 ms / 10 μV when the maximum off time of the switch 102 is 1 ms, the leakage current from the capacitor 100 is 1 nA when the switch 102 is off, and the allowable voltage fluctuation is 10 μV. = 0.1 μF.

  FIG. 6 shows an operation in the voltage variable mode as a third operation example of the current measuring apparatus 10 according to the present embodiment. The operation of this figure is substantially the same as the operation of FIG. 4 except for the points described below, and the description is omitted except for the differences.

  First, in the measurement preparation period T1, the test control unit 90 causes the current measurement unit 40 to output a reference supply voltage Vs that is lower than the ideal voltage supplied to the electronic device 20 during current measurement by a predetermined offset voltage Voff. . The reference supply voltage Vs is determined within a range in which the current measuring apparatus 10 can set the electronic device 20 during the measurement preparation period T1. As a result, the capacitor 100 stores the reference supply voltage Vs.

  When the setup of the electronic device 20 is completed, the current measurement period T2 is started. At the start of the current measurement period T2, the switch 152 (S2a) and the switch 102 (S2b) are disconnected. Thereby, the capacitor 100 can supply the accumulated reference supply voltage Vs to the adder 145.

  Next, after the elapse of a predetermined period, the test control unit 90 causes the voltage adjustment unit 160 to output the offset voltage Voff. As a result, the adder 145 outputs an adjusted reference supply voltage Vs + Voff obtained by adding the offset voltage Voff to the reference supply voltage Vs accumulated in the capacitor 100. Accordingly, the terminal voltage of the input terminal 25 increases so as to approach the voltage Vs + Voff. Here, the test control unit 90 may increase the offset voltage output from the voltage adjustment unit 160 from 0V to the final value Voff in a stepwise manner from 0V to the final value Voff. The resistance value and the capacitance of the resistor 164 and the capacitor 165 may be set so as to increase the offset voltage gently.

  Next, after the elapse of a predetermined period, the test control unit 90 turns off the switch 148 (S5). As a result, the capacitor 146 can supply the accumulated reference supply voltage Vs + Voff to the differential amplifier 112.

  Thereafter, similarly to the operation example of FIG. 4, the current value is measured, and the operation in the restoration period T3 is performed. In this restoration, the voltage adjustment unit 160 reduces the terminal voltage of the electronic device 20 by returning the offset voltage to 0V.

  Also in this operation example, measurement invalidity detection by the measurement invalidity detection unit 180 is performed. Here, in the voltage variable mode, the capacitor 50 and the capacitor 119 need to be charged as the voltage rises after the offset voltage is output from the voltage adjustment unit 160 until the terminal voltage finishes rising. For this reason, the supply current from the current measuring unit 30 temporarily increases, and the differential voltage of the differential calculator 122 can be larger than the threshold voltage of the voltage source 182. Therefore, the measurement invalidity detection unit 180 does not perform invalidity detection after the voltage adjustment unit 160 increases the offset voltage until the terminal voltage increases. In order to realize this, the measurement invalidity detection unit 180 may prohibit invalidity detection until the switch 148 (S5) is turned off.

  According to the operation example described above, the terminal voltage during the measurement preparation period T1 can be kept lower than the terminal voltage during the measurement period T2. Thereby, it can prevent that the temperature of the electronic device 20 rises with the operation | movement of the electronic device 20 during a setup period, and a high quiescent current is measured.

  Note that the voltage variable mode described above may be used together with the high-speed mode and / or the voltage correction mode. In this case, the switch 141 (S4) is turned off before the switch 148 (S5) is turned off after the terminal voltage has risen and stabilized, and the correction voltage corresponding to the terminal voltage at the time of current measurement is set to the capacitor 143. To supply from.

  FIG. 7 shows the result of simulating the noise reduction effect of the current measuring device 10 according to the present embodiment. FIG. 7 shows the noise gain (OLD (conventional)) according to the configuration of Patent Document 1 when the capacitor 50 is 1 μF, and the noise gain (NEW (this embodiment) of the high-speed mode current measuring unit 30 in the present embodiment). ).

  In the conventional configuration, the resistance and the capacitor provided in parallel between the output of the difference calculator and the electronic device 20 are 200Ω and 0.01 μF, and further provided between the resistance and the capacitor and the electronic device 20. The resistance obtained was 5Ω. In the conventional configuration, the noise of the voltage source is output from the difference calculator together with the noise of the output of the difference calculator.

  On the other hand, in the configuration of the present embodiment, the capacitor 100 is 0.1 μF, the resistor 113 is 1 KΩ, the resistor 114 is 40 KΩ, the resistor 118 is 200Ω, the capacitor 119 is 0.1 μF, and the resistance value when the switch 174 is on is 0. 1Ω was set. In the configuration of the present embodiment, the voltage of the capacitor 100 has no noise, and noise is generated in the voltage follower 172 and the differential amplifier 112. The noise of the voltage follower 172 is output after being multiplied by G (= Rf / Ri = 40), and the noise of the differential amplifier 112 is multiplied by 1 + G (= 41). In addition, regarding the resistance value Ri of the resistor 113 and the resistance value Rf of the resistor 114, since Rf / Ri is large, the noise of Ri becomes dominant. Further, the noise of the resistance value Rm of the resistor 118 is not amplified.

  FIG. 7 shows the result of simulating the noise gain generated by the conventional configuration and the configuration of the present embodiment under the above conditions. In this simulation, the resistance value of the electronic device 20 during current measurement was set to 100Ω. In addition, the output of the difference calculator 122 is supplied to the measurement unit 124 or the difference amplifier 130 via a low-pass filter that passes a band of 10 KHz or less.

  As shown in FIG. 7, according to the current measurement device 10 according to the present embodiment, noise generated in the supply current and the measurement current is greatly reduced with respect to the noise of about 10 KHz or less that is normally generated, as compared with the conventional case. be able to.

  Note that the resistance value of the resistor 113 is desirably smaller than the value obtained by converting the voltage noise of the differential amplifier 112 into the thermal noise of the resistor. That is, for example, when the voltage noise of the differential amplifier 112 is 5 nV / √Hz, when the voltage noise is converted into thermal noise of a resistor, the following resistance value Rx is obtained.

(Equation 6) Rx = En · En / (4 · k · t) = 5nV x 5nV / (4 x 1.38 x 10 ^-23 x 300) = 1.510KΩ
However, k is a Boltzmann constant, and t is an absolute temperature in the use environment.

  In this case, it is desirable that the resistance value Ri of the resistor 113 is smaller than the above Rx.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Current measurement apparatus 20 Electronic device 25 Input terminal 30 Current measurement part 35 Switch control part 40 Current measurement part 50 Capacitor 60 Capacitor 70 Resistance 90 Test control part 100 Capacitor 102 Switch 104 Resistance 110 Current supply part 112 Difference amplifier 113 Resistance 114 Resistance 116 Voltage follower 118 Resistor 119 Capacitor 120 Current measurement unit 122 Difference calculator 124 Measurement unit 126 Voltage source 128 Low-pass filter 130 Differential amplifier 132 Measurement unit 140 Correction unit 141 Switch 142 Resistance 143 Capacitor 144 Switch 145 Adder 146 Capacitor 147 Resistance 148 Switch 150 Power supply 152 Switch 155 Current measuring unit 160 Voltage adjusting unit 162 Voltage source 163 Switch 164 Resistor 165 Capacitor 166 Switch 170 Switch 172 Voltage follower 174 Switch 180 Measurement invalidity detection unit 182 Voltage source 184 Difference calculator 186 Invalid recording unit 200 Transistor 210 Transistor 502 Pattern generation unit 504 Signal input unit 506 Power supply unit 508 Determination unit

Claims (11)

A current measuring device for measuring a current received from an input terminal by an electronic device,
A first capacitor for storing a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
A first switch for connecting a power source to the first capacitor before current measurement to store the reference supply voltage and disconnecting the power source from the first capacitor during current measurement;
A current supply unit configured to supply current to the electronic device based on the reference supply voltage accumulated in the first capacitor and the terminal voltage of the input terminal during current measurement;
A first current measuring unit for measuring a supply current supplied to the electronic device,
The current supply unit is
A first differential amplifier that amplifies a difference obtained by subtracting the terminal voltage from the reference supply voltage and outputs a voltage added to the reference supply voltage;
A resistor connected between the output of the first differential amplifier and the input terminal, and supplying the supply current according to the difference between the output voltage of the first differential amplifier and the terminal voltage to the input terminal. ,
The first current measurement unit includes:
A differential calculator that outputs a differential voltage obtained by subtracting the terminal voltage on the input terminal side of the resistor from the output voltage on the first differential amplifier side of the resistor;
A correction unit that corrects the reference supply voltage by adding a correction voltage corresponding to the differential voltage to the reference supply voltage during current measurement;
The current supply unit supplies current based on the reference supply voltage and the terminal voltage corrected by the correction unit to the electronic device during current measurement,
The first current measurement unit includes:
Having a measurement unit for measuring the supply current based on the corrected differential voltage;
Current measuring device. The correction unit is
An adder for adding the correction voltage according to the differential voltage to the reference supply voltage;
The current measuring device according to claim 1, further comprising: a second capacitor that accumulates an output voltage of the adder and supplies the accumulated voltage to the first differential amplifier.   The correction unit is provided between the output of the adder and the second capacitor, and connects the second capacitor to the output of the adder for a predetermined period from the start of current measurement. 3. The current measuring device according to claim 2, further comprising a second switch that stores the output voltage of the adder and disconnects between the output of the adder and the second capacitor after the predetermined period has elapsed. A current measuring device for measuring a current received from an input terminal by an electronic device,
A first capacitor for storing a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
A first switch for connecting a power source to the first capacitor before current measurement to store the reference supply voltage and disconnecting the power source from the first capacitor during current measurement;
A current supply unit configured to supply current to the electronic device based on the reference supply voltage accumulated in the first capacitor and the terminal voltage of the input terminal during current measurement;
A first current measuring unit for measuring a supply current supplied to the electronic device;
A power supply for supplying the reference supply voltage to the first capacitor and the input terminal before current measurement;
A third switch for disconnecting the power source from the first capacitor and the input terminal during current measurement;
By adding a predetermined offset voltage to the reference supply voltage accumulated in the first capacitor during current measurement and supplying the current supply unit with the reference supply voltage, the terminal voltage during current measurement is supplied to the terminal before current measurement. A voltage adjustment unit that is higher than the voltage;
A current measuring device comprising: The third switch is
Provided between the wiring between the power source and the input terminal, the end of the first switch to which the first capacitor is not connected and the wiring contact between the power source and the output terminal of the power source And
A first transistor that cuts off a current from the output terminal side of the power supply to the contact side when the power supply is turned off between the output terminal of the power supply and the contact; and an output terminal of the power supply from the contact side A second transistor that interrupts current to the side in series;
The current measuring device according to claim 4. A current measuring device for measuring a current received from an input terminal by an electronic device,
A first capacitor for storing a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
A first switch for connecting a power source to the first capacitor before current measurement to store the reference supply voltage and disconnecting the power source from the first capacitor during current measurement;
A current supply unit configured to supply current to the electronic device based on the reference supply voltage accumulated in the first capacitor and the terminal voltage of the input terminal during current measurement;
A first current measuring unit for measuring a supply current supplied to the electronic device;
A power supply for supplying the reference supply voltage to the first capacitor and the input terminal before current measurement;
A third switch for disconnecting the power source from the first capacitor and the input terminal during current measurement;
A fourth switch provided between a terminal on the input terminal side of the third switch and a first differential amplifier of the current supply unit;
A fifth switch provided between the input terminal end of the resistor of the current supply unit and the input terminal;
A second current measuring unit for measuring a current supplied from the power source to the input terminal;
An operating current test for measuring an operating current received by the electronic device during operation, and a test controller for controlling a quiescent current test for measuring the quiescent current received by the electronic device during quiescence,
The test control unit
In the operating current test, the third switch is turned on, the fourth switch and the fifth switch are turned off, and the current supplied to the input terminal by the power source is supplied to the input terminal by the second current measuring unit. Let me measure as
In the quiescent current test, the third switch is turned off, the fourth switch and the fifth switch are turned on, and the electronic device is turned on based on the reference supply voltage and the terminal voltage stored in the first capacitor. The supplied current is measured as the quiescent current by the first current measuring unit,
Current measuring device. A current measuring device for measuring a current received from an input terminal by an electronic device,
A first capacitor for storing a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
A first switch for connecting a power source to the first capacitor before current measurement to store the reference supply voltage and disconnecting the power source from the first capacitor during current measurement;
A current supply unit configured to supply current to the electronic device based on the reference supply voltage accumulated in the first capacitor and the terminal voltage of the input terminal during current measurement;
A first current measuring unit for measuring a supply current supplied to the electronic device;
A measurement invalidity detection unit for detecting that the current measurement is invalid when the supply current measured by the first current measurement unit becomes larger than a preset threshold current during current measurement; ,
A current measuring device comprising: A power supply for supplying the reference supply voltage to the first capacitor and the input terminal before current measurement;
A third switch for disconnecting from the power source and the first capacitor and the input terminal during current measurement;
The current measurement apparatus according to claim 7, wherein the measurement invalidity detection unit turns on the third switch to supply current from the power source to the electronic device when detecting that the current measurement is invalid. A test apparatus for testing an electronic device,
A first capacitor for storing a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
A first switch for connecting a power source to the first capacitor before current measurement to store the reference supply voltage and disconnecting the power source from the first capacitor during current measurement;
A current supply unit configured to supply current to the electronic device based on the reference supply voltage accumulated in the first capacitor and a terminal voltage of the input terminal of the electronic device during current measurement;
A first current measuring unit for measuring a supply current supplied to the electronic device,
The current supply unit is
A first differential amplifier that amplifies a difference obtained by subtracting the terminal voltage from the reference supply voltage and outputs a voltage added to the reference supply voltage;
A resistor connected between the output of the first differential amplifier and the input terminal, and supplying the supply current according to the difference between the output voltage of the first differential amplifier and the terminal voltage to the input terminal. ,
The first current measurement unit includes:
A differential calculator that outputs a differential voltage obtained by subtracting the terminal voltage on the input terminal side of the resistor from the output voltage on the first differential amplifier side of the resistor;
A correction unit that corrects the reference supply voltage by adding a correction voltage corresponding to the differential voltage to the reference supply voltage during current measurement;
The current supply unit supplies current based on the reference supply voltage and the terminal voltage corrected by the correction unit to the electronic device during current measurement,
The first current measurement unit includes:
Having a measurement unit for measuring the supply current based on the corrected differential voltage;
Test equipment. A current measurement method for measuring a current received from an input terminal by an electronic device,
A reference supply voltage accumulating stage for accumulating in the first capacitor a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
Connecting a power supply to the first capacitor before current measurement to store the reference supply voltage and controlling the first switch to disconnect the power supply from the first capacitor during current measurement;
A first current supply step of supplying current to the electronic device based on the reference supply voltage stored in the first capacitor and a terminal voltage of the input terminal during current measurement;
A reference voltage correction step of adding a correction voltage corresponding to a differential voltage generated across the resistor provided in the current path to the supply current supplied to the electronic device to the reference supply voltage;
A second current supply stage for supplying a current based on the corrected reference supply voltage and the terminal voltage of the input terminal to the electronic device during current measurement;
A current measurement step of measuring a corrected supply current supplied to the electronic device;
A current measuring method comprising: A test method for testing an electronic device, comprising:
A reference supply voltage accumulating stage for accumulating in the first capacitor a reference supply voltage that is a reference for a voltage supplied to the electronic device during current measurement;
Connecting a power supply to the first capacitor before current measurement to store the reference supply voltage and controlling the first switch to disconnect the power supply from the first capacitor during current measurement;
A first current supply stage for supplying to the electronic device a current based on the reference supply voltage stored in the first capacitor and a terminal voltage of an input terminal of the electronic device during current measurement;
A reference voltage correction step of adding a correction voltage corresponding to a differential voltage generated across the resistor provided in the current path to the supply current supplied to the electronic device to the reference supply voltage;
A second current supply stage for supplying a current based on the corrected reference supply voltage and the terminal voltage of the input terminal to the electronic device during current measurement;
A current measurement step of measuring a corrected supply current supplied to the electronic device;
A test method comprising:

Images