JPH07209372A - Method and apparatus for measuring current - Google Patents

Abstract

PURPOSE:To provide a method and an apparatus for measuring current at the terminal of a device to be measured without requiring any current probe. CONSTITUTION:A resistor 12 having resistance R(<<r) is inserted between a constant voltage source 1 having inner resistance (r) and a device 2 to be measured. A digitizer 13 monitors the voltage at the joint of the device 2 and an additional capacitor 4. The current measuring apparatus is constituted as mentioned above. The current measuring method comprises a step for operating the capacitance C of the capacitor C provided additionally at the end of the device to be measured by applying a voltage thereto from the constant voltage source 1 through the resistor R, and a step for operating the current being consumed by the device 2 based on a voltage waveform Vs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, when measuring the terminal current of a device under test, does not require a current probe,
The present invention relates to a current measuring device and method for measuring a current.

[0002]

2. Description of the Related Art In semiconductor test equipment, it is necessary to measure the terminal current of a device under test (DUT). This terminal current is not limited to a static current, that is, a current when the device under test holds a constant test pattern. It is necessary to measure the dynamic current, that is, the current when the internal state is changing by applying a constant test pattern to the device under test.

FIG. 5 shows a conventional semiconductor test apparatus.
It is a block diagram which shows the measurement example of a power supply current. As shown in FIG. 5, the constant voltage source 1 and the DUT 2 are connected, and the bypass capacitor 4 is connected to the connection portion.
The constant voltage source 1 supplies a constant voltage value V ₀ . The bypass capacitor 4 having the capacitance C is usually connected for the purpose of complementing the high frequency response speed of the constant voltage source 1 system, and the inductance of the wire rod wired between the constant voltage source 1 and the DUT 2. It compensates for the deterioration of high-frequency characteristics due to components. Therefore, normally, the bypass capacitor is placed in the immediate vicinity of the terminals of the DUT 2. Further, the capacitance value C is usually empirically determined.

A current probe 5 is inserted between the DUT 2 and the capacitor 4. The output of the current probe 5 is input to the oscilloscope 3 to monitor the waveform. An example of the monitor waveform is shown in FIG. When the consumption current I _{L of the} DUT 2 changes as shown in FIG. 6 (A), the monitor voltage V _L induced by the current probe 5 changes as shown in FIG. 6 (B). The change in the current I _L can be monitored as the differential value V _L. Since the height of the peak of the differential value is proportional to the change value of the current, the current value is calculated backward.

Thus, when the current probe 5 is provided, (1) the current probe must be inserted between the DUT 2 and the capacitor 4, and the distance between the DUT and the decap becomes long. For this reason, the inductance component and the like increase, leading to characteristic deterioration. (2) Further, since a space for installing the current probe is required, it is unavoidable to change the existing shape of the performance board on which the DUT peripheral circuit is mounted. (3) Then, the packaging density of the performance board having a large number of DUTs is reduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the above-mentioned conventional techniques, and when measuring the terminal current of a device under test,
It is intended to provide a current measuring device and method for measuring a current by observing a terminal voltage of a DUT without requiring a current probe.

[0007]

[Means for Solving the Problems]

(Solution of Claim 1) In a device for measuring a current of a device under test 2, a constant voltage source 1 having an internal resistance r;
A resistor 12 having a value R such that r << R is provided between the device under test 2 and the device under test 2. Then, the switch 11 that short-circuits the resistor 12 is provided. Then, a digitizer 13 for monitoring the voltage at the connection point between the device under test 2 and the added capacitor 4 is provided. Then, the current value is measured from the monitor waveform of the digitizer 13 to configure a current measuring device.

(Means for Solving the Claim 2) Device under Test 2
A constant voltage source 1 having an internal resistance r is provided in the device for measuring the current. Then, a resistor 12 having a value R of r << R is provided between the constant voltage source 1 and the device under test 2. Then, the switch 11 that short-circuits the resistor 12
To provide. Then, a buffer 101 for buffering the voltage at the connection point between the device under test 2 and the added capacitor 4 is provided. Then, the buffer value is
An ADC 102 for digital conversion is provided. Then, the memory unit 103 for storing the digital value is provided. Then, the calculation unit 104 that calculates the current value based on the stored value.
To provide. Then, a current measuring device is configured.

(Means for Solving Claim 3) Device under test 2
In the method of measuring the current, first, the device to be measured 2 is removed, a voltage is applied from the constant voltage source 1 through the resistance value R to the capacitor C added to the end of the device to be measured, and its voltage waveform The capacitance C is calculated from V _S. Next, a voltage is applied from the constant voltage source 1 having the internal resistance r to the device under test 2 and the added capacitor C. Then, the current consumption method of the device under test 2 is obtained by performing an operation based on the voltage waveform V _S to configure the current measuring method.

[0010]

According to the present invention, first, the value C of the capacitor 4 is
Is measured as follows. First remove the DUT2,
The switch 11 is opened and the voltage V ₀ is supplied from the constant voltage source 1. Then, the current passing through the resistor R from the constant voltage source 1 charges the capacitor 4. It is generally known that this waveform has an exponential function, and the unit time t1 is measured, and the capacitance value C can be calculated from C = t1 / R 2.

Next, the current consumption value I _L of the device is measured as follows. The device current consumption _IL is constant voltage source 1
Let I ₀ be the current supplied from the capacitor and I _C be the current supplied from the capacitor 4, then I _L = I ₀ + I _C. Here, I ₀ = (V ₀ −V _S ) / r, and I _C = C · ΔV _S / Δt. Therefore, I _L = V ₀ / r−V _S / r + C · ΔV _S / Δt. Where V ₀ , r, C are known and V _S , ΔV
_{Since S} and Δt can be respectively observed, I _L can be calculated.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in FIG. 1, there is a constant voltage source 1 having an internal resistance r, and a resistor 12 having a value R of r << R is provided between the constant voltage source 1 and the DUT 2. Then, a switch 11 is provided on the resistor 12 to set a resistance value R
Is configured to be short-circuited. To the terminal of DUT2,
A digitizer 13 that connects the capacitor 4 and monitors the voltage waveform at the same connection point is provided. Then, the current conversion unit 14 for converting the observation value of the digitizer 13 into the current value is provided to obtain the output result.

The conversion into a current value is performed by the following method. First, the value C of the capacitor 4 is measured. (1) First, the DUT 2 is removed, the switch 11 is opened, and the voltage V ₀ is supplied from the constant voltage source 1.
Then, the current passing through the resistor R from the constant voltage source 1 charges the capacitor 4. Therefore, the voltage at the monitor point V _S is
A waveform is drawn as shown in FIG. It is generally known that this waveform is an exponential function, and the unit time t1
And the capacitance value C can be calculated from C = t1 / R.

Next, the current consumption value I _L of the device is measured. (2) Consumption current I _L of the device, when the current supplied from the constant voltage source 1 I _0, the current supplied from the capacitor 4 to I _C, a _{I L = I 0 + I C} . Here, I ₀ = (V ₀ −V _S ) / r, and I _C = C · ΔV _S / Δt. Therefore, I _L = V ₀ / r−V _S / r + C · ΔV _S / Δt. Where V ₀ , r, C are known and V _S , ΔV
_{Since S} and Δt can be respectively observed, I _L can be calculated. That is, the consumption current I _L shown in FIG. 3B can be obtained from the observed waveform V _{S of} FIG. 3C.

(Embodiment 2) In the above-mentioned embodiment, the digitizer 13 and the current converter 14 are added in addition to the constant voltage source 1 to form a current measuring device. It can also be configured as 4.

As shown in FIG. 4, a constant voltage source 1 having an internal resistance r is provided. A resistor 12 having a value R of r << R is provided between the constant voltage source 1 and the DUT 2. A switch 11 is provided on the resistor 12 so that the resistance value R can be short-circuited. The capacitor 4 is connected to the terminal of the DUT 2, but the buffer 1
01 is provided to input a monitor signal. Buffer 1
01 is an AD that converts an analog signal into a digital signal
C102 is provided and connected. Then, the ADC 102
The digital output signal from is stored by providing the memory unit 103. The monitor data in the memory unit 103 is converted into a current value by providing the arithmetic unit 104. Then, the display is performed. Here, the method of measuring the current consumption value I _L of the device is the same as in the first embodiment described above.

[0018]

Since the present invention is configured as described above, it has the following effects. Since the device and method for monitoring and calculating the voltage waveform when measuring the terminal current of the device under test are configured, the current measuring device and method can be provided without the need for a current probe.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2A shows a voltage at a monitor point V _S.

FIG. 3 (B) shows a consumed current I _L. (C) shows the observed waveform V _S.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram showing an example of measurement of a conventional power supply current.

FIG. 6A is a conventional example of monitoring the consumed current I _L. (B) An example of a conventional monitor voltage V _L.

[Explanation of symbols]

 1 constant voltage source 2 DUT 3 oscilloscope 4 capacitor 5 current probe 11 switch 12 resistance 13 digitizer 14 current converter 100 current measuring device 101 buffer 102 ADC 103 memory unit 104 arithmetic unit 105 display unit

Claims (3)

[Claims] 1. A device for measuring a current of a device under test 2, wherein a resistor 12 having a value R of r << R is provided between a constant voltage source 1 having an internal resistance r and the device under test 2. Is provided, a switch 11 for short-circuiting the resistor 12 is provided, a voltage at a connection point between the device under test 2 and the added capacitor 4 is monitored, a digitizer 13 is provided, and a current value is measured from a monitor waveform of the digitizer 13. A current measuring device characterized by the above. 2. An apparatus for measuring a current of a device under test 2 is provided with a constant voltage source 1 having an internal resistance r, and r << R is provided between the constant voltage source 1 and the device under test 2. A resistor 12 having a value R is provided, a switch 11 that short-circuits the resistor 12 is provided, and a buffer 101 that buffers the voltage at the connection point between the device under test 2 and the added capacitor 4 is provided.・ ADC1 for digital conversion
02 is provided, a memory unit 103 for storing the digital value is provided, and a calculation unit 104 for calculating a current value based on the stored value is provided, and the above is provided. 3. A method of measuring the current of a device under test 2, wherein the device under test 2 is first removed, and a constant voltage source 1 is passed through a resistance value R to a capacitor C added to the end of the device under test. , Voltage is applied, the capacitance C is calculated from the voltage waveform V _S , and then voltage is applied from the constant voltage source 1 having the internal resistance r to the device under test 2 and the added capacitor C. A current measuring method characterized in that the current consumption of the device under test 2 is obtained by performing an operation based on the voltage waveform V _S.