JPS60253883A - Constant current load/constant voltage applied current measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measurement of current and voltage with a simple construction by having the inversion input side of an operational amplifier switched over to a current input/output terminal of a constant current load circuit or to a switching voltage setting end of a diode bridge. CONSTITUTION:This measuring apparatus is made up of a current detection circuit 28, an A/D converter 31, a diode bridge 43, an operational amplifier 52 and the like. The noninversion input side of the operational amplifier 52 is connected to a switching voltage setting terminal 48 while the inversion input side thereof is connected to a current input/output terminal 46 through a switch 53 or to a switching voltage setting terminal 55 of the diode bridge 43 through a switch 54. An element 17 to be measured is connected and then, a switch 53 is turned OFF while a switch 54 is turned ON whereby the element 17 being measured is loaded with a constant current to enable the measurement of the voltage. In addition, when the switch 54 is turned OFF while the switch 53 is turned ON, a constant voltage is applied to the element 17 being measured 17 to enable the measurement of the current.

Description

Detailed Description of the Invention "Industrial Application Field" This invention is used, for example, in DC characteristic testing of integrated circuits of semiconductor logic circuits. This invention relates to a constant current load/constant voltage applied current measuring device for measuring constant current load and constant voltage applied current.゛``Prior art'' ゛ □ In DC characteristic testing of semiconductor logic integrated circuits, the voltage generated at the application terminal when a constant current is applied to the semiconductor under test (the other side to be measured) is measured, and the voltage generated at the application terminal is measured. When a constant voltage is applied, the current flowing through the application terminal is measured. Conventionally, a constant current/constant voltage measuring device for measuring such DC characteristics has been constructed as shown in FIG.

That is, for example, when a digital value is set, the output of the D/A converter 11, which outputs a constant voltage or constant current corresponding to the digital value, is supplied to the inverting input side of the operational amplifier 13 through the resistor 12. The non-inverting input side of the operational amplifier 13 is grounded, and the output side is connected to a test semiconductor logic circuit element (hereinafter referred to as an element under test or an element under test) 17 through a current detection resistor 14 and a switch 15. be done. This output terminal 16 is connected to a switch 18 f: iM, which is a buffer circuit 19.
The output of the buffer circuit 19 is connected to the inverting input side of the operational amplifier 13 through a resistor 21 and a switch 22. The output side of the operational amplifier 13 is connected through a resistor 23 to the non-inverting input side of an operational amplifier 24, and this non-inverting input side is connected to ground through a resistor 25. Further, the output of the buffer circuit 19 is connected to the inverting input side of the operational amplifier 24 through a resistor 26, and a feedback resistor 27 is connected between this inverting input side and the output side of the operational amplifier 24. These resistors 23, 25, 26, 27 and operational amplifier 24 constitute a current detection circuit 28. The output side of operational amplifier 24 is connected to A/D converter 31 through switch 29 . The output of buffer circuit 19 is connected to A/D converter 31 through switch 32. Furthermore, the inverting input side of the operational amplifier 13 is connected through a switch 33 and further through a resistor 34 to the output side of the operational amplifier 24.

When performing a test, the switches 15 and 18 are always turned on, and in this state, a constant voltage is applied to the device under test 1.
To measure the current applied to output terminal 7 and flowing to output terminal 16 at that time, switches 22 and 29 are turned on, and switch 3 is turned on.
2.33 is set to OFF. In the case of resistors 12 and 21
．． Furthermore, a constant voltage determined by the output voltage of the D/A converter 11 appears at the output terminal 16, and is applied to the devices under test 1 and 7. At this time, the current flowing through the device under test 17 passes through the current detection resistor 14. The voltage across this resistor 14 is detected by a current detection circuit 28, and its output is A
The signal is converted into a digital signal by the /D converter 31, and this is displayed. Voltage of output terminal 16 and buffer circuit 19
Therefore, the current flowing through the output terminal 16 can be determined from the voltage across the current detection resistor 14 detected by the current detection circuit 28 and the resistance value of the resistor 14.

To supply a constant current to the device under test 17 and measure the voltage at the output terminal 16 at that time, switch 22.29 is turned OFF and switch 32.33 is turned ON. At this time, the output voltage of A/D converter 11, resistors 12, 34 and 1
A constant current determined by each resistance value of 4 is applied to the device under test 1.
7. The voltage at the output terminal 16 at this time is supplied to the A/D converter 31 through the buffer circuit 19 and the switch 32 for measurement.

On the other hand, since the specified load condition tq is applied to the device under test when performing a functional test, a constant current load circuit is connected to each terminal pin of the device under test 17 in order to perform the test with a limited load applied. There is a test device in which a predetermined constant current is applied to each terminal bin of the device under test. That is, as shown in FIG. 4, the high potential power supply terminal 41
The constant current source 42 connected to the diode bridge 43 is connected to the connection end where the anodes are connected to each other, and the connection end of the diode bridge 43 where the cathodes are connected to each other is connected to the constant current source #4.
4 to a low potential power supply terminal 45. One cathode and anode connection end of the diode bridge 43 is connected to a current input/output terminal 46, and this current input/output terminal 46 is connected to the device under test 17. Furthermore, the cathode and anode connection ends of the pond of the diode bridge 43 are connected to the output side of the buffer circuit 47, and the input side of the buffer circuit 47 is connected to the switching voltage terminal 48.

For example, the constant current values of the constant current sources 42 and 44 are set to the same value, and if the voltage Vj applied to the switching voltage terminal 48 is controlled to be higher than, for example, the voltage of the input/output terminal 46, a part of the constant current of the constant current 42 Alternatively, all the signals are supplied to the device under test 17 through the input/output terminal 46. When the voltage Vt of the switching voltage terminal 48 is lowered than the voltage of the input/output terminal 46, part or all of the constant current of the constant current source 42 is drawn into the buffer circuit 47 side, and the voltage is transferred from the device under test 17 through the input/output terminal 46. Constant current source 44
A current flows through. In other words, the current from the constant current source 44 is supplied to the device under test 17. In this state where a constant current load is applied to the device under test 17, the input/output terminal 46 at that time
voltage to comparator 49.51.

Vh-
V,! A determination is made as to whether or not it is time.

Since the constant current load circuit is provided in this way, a constant current is applied to the device under test 17 and the input/output terminal 46 at that time is
By measuring the voltage or determining the voltage range, it becomes possible to perform constant current applied voltage measurement.

``Problems to be Solved by the Invention'' However, with a constant current load circuit, constant voltage applied current measurement cannot be performed. For this reason, conventionally, a DC characteristic tester shown in FIG. 3 has been used. In this DC characteristic tester, the operational amplifiers 13 and 19 were required to supply relatively large currents, which made them expensive, and the number of switches was large, which also made them expensive. When testing a device under test 17 that has a large number of measurement terminals, switching each terminal one after another will take a long time to measure, and using multiple DC characteristic testers will make the entire device extremely expensive. Become.

The purpose of this invention is to be able to perform both constant voltage applied current ff1lJ constant current applied voltage measurement and constant current applied voltage measurement, and can be constructed at low cost, so that many terminals or many objects to be measured can be measured simultaneously. An object of the present invention is to provide a constant current load/constant voltage applied current measuring device that allows testing to be performed using an inexpensive device and further reduces measurement time significantly.

"Means for Solving the Problem" According to the present invention, a constant current circuit on a high potential side and a constant current circuit on a low potential side are switched by applying a switching voltage to a diode bridge through an operational amplifier. The current load circuit is configured such that the inverting input side of the operational amplifier can be switched between a current output terminal of the constant current load circuit and a switching voltage setting terminal of the diode bridge. Further, the output current of the operational amplifier can be detected by a current detection circuit.

Embodiment FIG. 1 shows an example of a constant current load/constant voltage applied current measuring device according to the present invention, and parts corresponding to those in FIGS. 3 and 4 are given the same reference numerals. In this embodiment, an operational amplifier 52 is provided, which is used to set the switching voltage Vi at the terminal 48 to the diode bridge 43, similar to the operational amplifier of the buffer circuit 47 in the circuit shown in FIG. , the non-inverting input side of the operational amplifier 52 is connected to the switching voltage setting terminal 48, and the inverting input side is connected to the switch 53.
It is connected to the current input/output terminal 46 through the switch 54, and to the side connected to the switching voltage setting end 55 of the diode bridge 43 and the output side of the operational amplifier 52 through the switch 54. Furthermore, the output side of the operational amplifier 52 is connected to a switching voltage setting terminal 55 of the diode bridge 43 through a current detection resistor made of 14-karat gold. Both ends of the current detection resistor 14 are connected to a current detection circuit 28 , and the output of the current detection circuit 28 is connected to an A/D converter 31 . In this example, the diode bridge 43 side of the current detection resistor 14 is connected to the current detection circuit 28 through a buffer circuit 56.

When operating this configuration as a constant current load circuit, the switch 53 is turned off and the switch 54 is turned on. As a result, the inverting input side of the operational amplifier 52 is connected to the connection point 5 between the current detection resistor 14 and the diode bridge 43.
5, and the resistance value of the current detection resistor 14 is a small value. Therefore, the operational amplifier 52 functions in the same manner as the buffer circuit 47 in FIG. , set voltage Vt(i-
By switching, the constant current of the constant current source 42 can be supplied to the device to be measured 17 through the input/output terminal 46, or the constant current of the constant current source 44 can be supplied to the device to be measured 17. In other words, a constant current can be supplied to the device under test 17 as a load current, and if necessary, the constant current supply voltage can be measured by measuring the voltage at the terminal 46 at this time. In this case, if the device under test 17 is a logic circuit, the comparators 49, 51 may only determine whether the voltage is between vh and V and whether the voltage is above VhR or below V and u.

When performing constant voltage applied current measurement, switch 54 is turned OFF.
F and the switch 53 is turned on. In this case, it becomes a constant voltage circuit, and the voltage EVt of the switching voltage setting terminal 48 is applied to the input/output terminal 46, and this is applied to the device under test 17. By making the constant current values of the constant current sources 42 and 44 equal, the current Id flowing through the input/output terminal 46 and the current ■ flowing through the current detection resistor 14 become equal. Therefore constant voltage! When EVj is applied to the device under test 17, the input/output terminal 4
6 can be measured by the A/D converter 31 by detecting the voltage across the current detection resistor 14 with the current detection circuit 28.

In addition to supplying the output of this current detection circuit 28 to the A/D converter 31, the output is switched to the voltage at the input/output terminal 46 by a switch 57 as shown in FIG. 51 and if a high level is obtained from either of the comparators 49 and 51, the OR circuit 58
It is also possible to output a signal indicating that the device under test 17 is defective. That is, it is also possible to measure using the analog comparators 49 and 51 used in conventional constant current load tests, and using the reference voltages vh and Vi at that time as a base saw.

``Effects of the Invention'' As mentioned above, according to the present invention, only a constant current detection circuit 28 and switches 53 and 54 are added to the constant current load circuit that has been conventionally commonly used in analog test equipment. Compared to the conventional DC characteristic tester shown in FIG. 3, the structure is simpler than the conventional DC characteristic tester shown in FIG. , operational amplifier 13 in FIG.
Unlike ゜19, two switches are not required, and conventionally four switches 22, 29, 32 and '33 are required, but only two switches 53 and 54 are required, and the configuration can be made at a lower cost. can. Therefore, since the structure can be constructed at a relatively low cost, a large number of pin terminals and devices to be measured can be individually provided and measured at the same time, and measurement can be performed in a short time.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an example of a constant current load/constant voltage applied current measuring device according to the present invention, Fig. 2 is a connection diagram showing a partial modification thereof, and Fig. 3 is a connection diagram showing a conventional constant voltage applied current measurement and constant voltage applied current measuring device. A connection diagram showing a current applied voltage measuring device, and FIG. 4 is a connection diagram showing a conventional constant current load circuit. 14: Current detection resistor, 17: Device under test, 28: Current detection circuit, 32: Constant current source on high potential side, 44:
Constant current source on low potential side, 46: Current input/output terminal, 48: Switching voltage setting terminal. Patent applicant: Takeda Riken Kogyo Co., Ltd. Agent: Taku Kusano Published by Muno

Claims (1)

[Claims] (1) A first constant current circuit connected to the high potential side, a second constant current circuit connected to the low potential side, a diode bridge that switches and supplies the current of these constant current circuits to the current input/output terminal, and the diode bridge. a constant current load circuit configured with an operational amplifier that provides a switching setting voltage to the switch; and a switch that selectively connects the inverting input side of the operational amplifier to the current input/output terminal and the switching voltage setting terminal of the diode bridge. and a circuit for detecting the output current of the operational amplifier.