JP2001125651A - Current limiting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current limiting circuit which can shorten the test time of a measured sample by shortening the time needed to raise a source voltage applied to the measured sample up to a set value. SOLUTION: The current limiting circuit is equipped with a D/A converter 1A which outputs a voltage signal for supplying electric power to a DUT 6, an inverting amplifier circuit (resistances 2A and 2B and operational amplifier 3A) which amplifies the voltage signal, a capacitor 5 which absorbs variation of the power source supplied to the DUT 6, an operational amplifier 3B for setting the amplification factor of the inverting amplifier circuit, a transistor 4, and a resistor 2C; and a source voltage monitoring means (voltage monitor 7) monitors the voltage level of the voltage signal outputted by the D/A converter 1A and an amplification factor varying means (diode 8, resistors 2D and 2E, and switch 9) varies the setting of the amplification factor of the amplification factor setting means according to the monitoring result of the source voltage monitoring means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a current limiting circuit for a program power supply in an IC test apparatus.

[0002]

2. Description of the Related Art A conventional current limiting circuit for a program power supply will be described with reference to FIG. FIG. 3 is a diagram showing a main configuration of a current limiting circuit of a program power supply in a conventional IC test apparatus. In FIG. 3, the conventional current limiting circuit 20
Is composed of D / A converters 1A and 1B, resistors 2A, 2B, and 2C, operational amplifiers 3A and 3B, a transistor 4, and a capacitor 5. The conventional current limiting circuit 2 has one end connected to a DUT (Device Under
Test) 6.

First, the configuration of the conventional current limiting circuit 20 will be described. An output terminal of the D / A converter 1A is connected to a resistor 2A, and the other end of the resistor 2A is connected to a resistor 2A.
B and the negative input terminal of the operational amplifier 3A.
The other end of the resistor 2B is connected to the DUT 6, the positive input terminal of the operational amplifier 3A is grounded, and the output terminal is connected to the DUT 6.

On the other hand, the output terminal of the D / A converter 1B is connected to the positive input terminal of the operational amplifier 3B, the negative input terminal of the operational amplifier 3B is connected to the emitter terminal of the transistor 4, and its output terminal is connected to the transistor 4 It is connected to the base terminal.

[0005] The collector terminal of the transistor 4 is connected to an A terminal which is a current limiting terminal of the operational amplifier 3A, and its emitter terminal is connected to a B terminal which is a negative power supply voltage via a resistor 2C. The capacitor 5 has one end connected to the DUT 6 and the other end grounded.

Next, the operation of the program power supply and the conventional current limiting circuit 20 will be described. Program power is D
A power is applied to the DUT 6 when an operation test of the UT 6 is performed.

In the current limiting circuit 20, when digital information of a voltage applied to the DUT 6 is input to the D / A converter 1A, the D / A converter 1A converts the digital information into a voltage value which is an analog value. The operational amplifier 3
It outputs to the negative input terminal of A and the resistor 2A.

Since the positive input terminal of the operational amplifier 3A is grounded, the operational amplifier 3A operates as an inverting amplifier circuit having a resistor 2A corresponding to the input resistance and a resistor 2B corresponding to the feedback resistance. If the output voltage of the D / A converter 1A is V1, the resistance of the resistor 2A is R1, and the resistance of the resistor 2B is R2, the output voltage V2 of the operational amplifier 3A is V2 =-(R2 / R1). * V1 (1) and the output voltage V2 of the operational amplifier 3A is DUT6
Is applied to

Therefore, as shown in equation (1),
By arbitrarily setting the voltage information to be input to the D / A converter 1A, the output voltage V1 of the D / A converter 1A can be arbitrarily set, and the output voltage V2 of the operational amplifier 3A is set to the DUT 6 which is the output voltage V2. Any voltage can be applied.

The output current IO of the operational amplifier 3A is
Is a current IA flowing from a terminal A, which is a current limiting terminal of the operational amplifier 3A, to a terminal B, which is a negative power supply voltage.
Is controlled by That is, assuming that the current amplification factor of the operational amplifier 3A is G, the output current IO of the operational amplifier 3A
Is: IO = G * IA (2) Therefore, as shown in the equation (2), by controlling this current IA, the current I
O can be arbitrarily limited.

In the current limiting circuit 20, when digital information of the limiting current for determining the value of the current IA is input to the D / A converter 1B, the D / A converter 1B converts the information into a voltage value which is an analog value. Then, the signal is output to the operational amplifier 3B.
The operational amplifier 3B controls the base voltage of the transistor 4 so that the voltage at the connection point between the negative input terminal and the resistor 2C is equal to the output voltage of the D / A converter 1B.

Here, the output voltage of the D / A converter 1B is
D, if the voltage value of the terminal B, which is a negative power supply voltage, is VB and the resistance value of the resistor 2C is RC, the current IA is IA = (VB−VD) / RC (3) By substituting the IA of the equation (3) into the equation (2), the output current IO to the DUT 6 is limited to the following equation: IO = G * (VB−VD) / RC (4)

As described above, in the conventional current limiting circuit 20, by providing the D / A converter 1B, the value of the current to be limited can be arbitrarily set, and the output current IO of the operational amplifier 3A can be set when an abnormality occurs. Is excessive, it is possible to prevent the program power supply circuit and the DUT 6 from being damaged by limiting the current.

The capacitor 5 connected to the DUT 6 is for absorbing fluctuations in the power supply supplied to the DUT 6, and when a voltage is applied from the program power supply to the DUT 6, the capacitor 5 is connected to the capacitor 5 at the same time. Is also being charged.

[0015]

However, in the conventional current limiting circuit 20, as shown in FIG. 3, when the set voltage of the program power supply is VO, the limit value of the output current is IO, and the capacitance of the capacitor 5 is C, When the value of the output current limit value IO is very small, the time T required for the input voltage of the DUT 6 to reach the set voltage VO from 0 V by charging the capacitor 5 is given by: IO * T = C * VO. From 5), T = (C * VO) / IO (6)

Therefore, when the current limit value IO is set small, it takes time until the power supply voltage of the DUT 6 reaches the set value, and as a result, there is a problem that the test time of the DUT 6 increases.

[0017]

In order to solve the above-mentioned problems, the invention described in claim 1 is based on a sample to be measured (for example, FIG. 1).
Power supply signal output means (for example, the D / A converter 1 of FIG. 1) for outputting a voltage signal for supplying power to the DUT 6 of FIG.
A), amplifying means for amplifying the voltage signal output by the power signal output means (for example, an inverting amplifier circuit composed of resistors 2A and 2B and an operational amplifier 3A in FIG. 1), and amplification by the signal amplifying means Power fluctuation absorbing means (for example, the capacitor 5 in FIG. 1) that absorbs fluctuations in the power supplied to the sample to be measured by the applied voltage signal
And a gain setting means (for example, a D / A converter 1B, an operational amplifier 3B, a transistor 4, and a resistor 2C in FIG. 1) for setting an amplification factor in the signal amplifying means. Power supply voltage monitoring means (for example, the voltage monitor 7 in FIG. 1) for monitoring the voltage level of the voltage signal output by the power supply signal output means, and the amplification factor setting means based on the monitoring result of the power supply voltage monitoring means (For example, the resistors 2D and 2E, the diode 8, and the switch 9 in FIG. 1) for changing the setting of the amplification factor.

According to the first aspect of the present invention, power supply signal output means for outputting a voltage signal for supplying power to the sample to be measured, and amplification for amplifying the voltage signal output by the power supply signal output means Means, a power supply fluctuation absorbing means for absorbing fluctuations in the power supplied to the sample to be measured by the voltage signal amplified by the signal amplifying means, and an amplification factor setting means for setting an amplification factor in the signal amplifying means; Wherein the power supply voltage monitoring means monitors the voltage level of the voltage signal output by the power supply signal output means, and the amplification factor changing means, based on the monitoring result of the power supply voltage monitoring means, Change the setting of the amplification factor of the amplification factor setting means.

According to a second aspect of the present invention, in the current limiting device of the first aspect, the amplification factor changing means includes:
When the power supply voltage monitoring means detects that the voltage level of the voltage signal output by the power supply signal output means has reached a predetermined voltage value, the setting of the amplification rate of the amplification rate setting means is reduced. Is also good.

Further, as in the invention according to claim 3, in the current limiting circuit according to claim 1 or 2, the amplification factor changing means includes a diode (for example, the diode 8 in FIG. 1) and a switch (for example, The switch 9) of FIG. 1 is included, and by controlling ON / OFF of this switch,
The configuration may be such that the setting of the amplification factor of the amplification factor setting means is changed.

Therefore, according to the first to third aspects of the present invention, the power supply voltage can be applied to the sample to be measured at high speed, and the test time of the sample to be measured can be shortened as a whole test.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a current limiting circuit according to the present invention will be described below in detail with reference to FIGS. First, the configuration will be described.

FIG. 1 is a diagram showing a main configuration of a current limiting circuit 10 according to an embodiment to which the present invention is applied. In FIG. 1, the same components as those of the conventional current limiting circuit 20 shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, the current limiting circuit 10
D / A converters 1A and 1B, resistors 2A, 2B, 2C,
2D and 2E, operational amplifiers 3A and 3B, transistor 4, capacitor 5, voltage monitor 7, diode 8, and switch 9. Among them, the portion added to the conventional current limiting circuit 20 includes resistors 2D and 2D.
E, a voltage monitor 7, a diode 8, and a switch 9.

The diode 8 has an anode terminal connected to the A terminal which is a current limiting terminal of the operational amplifier 3A, and a cathode terminal connected to the resistor 2D and the resistor 2E.

The other end of the resistor 2D is connected to a terminal B which is a negative power supply voltage, and the other end of the resistor 2E is connected to a switch 9
Grounded.

A voltage monitor 7 is connected to the output of the D / A converter 1A in parallel with the resistor 2A, and the output of the voltage monitor 7 is used as a control signal for controlling the switch 9. It is connected to the.

The voltage monitor 7 monitors the voltage of the D / A converter 1A, and controls the low level until the voltage output of the D / A converter 1A reaches the set voltage VO from 0V. A signal is output to the switch 9, and when the voltage reaches the set voltage VO, the control signal is changed from a low level to a high level.

The switch 9 is turned off when the control signal input from the voltage monitor 7 is at a low level,
The other end of E is open, and when this control signal is at a high level, it is turned on, and the other end of resistor 2E is grounded.

Here, when the switch 9 is OFF, the diode # 8 is biased in the forward direction and turns ON, and the diode 8 and the resistor 2D are connected from the terminal A for limiting the current of the operational amplifier 3A. Through the negative power supply voltage B
Current IB flows to the terminal.

At this time, the current flowing from the terminal A, which is a current limiting terminal of the operational amplifier 3A, to the terminal B, which is a negative power supply voltage, is a constant current IA preset by the D / A converter 1B and this current IA. IB, and the limit of the output current to the DUT 6 is a value larger than the set value by the current IB.

When the switch 9 is ON,
Since the other end of the resistor 2E is grounded, the voltage at the cathode terminal of the diode 8 is higher than the voltage at the A terminal, which is a current limiting terminal, by the voltage division due to the resistance ratio between the resistor 2D and the resistor 2E. When the voltage is lower than the ground voltage (0 V), the diode 8 is reverse-biased and turned off,
A current IC flows from the ground point to the terminal B, which is a negative power supply voltage, via the switch 9, the resistor 2E, and the resistor 2D.

As a result, the constant current IA preset by the D / A converter 1B flows from the terminal A, which is a current limiting terminal of the operational amplifier 3A, to the terminal B, which is a negative power supply voltage, and is output to the DUT 6. The current limit is the same as the set value.

Next, the operation will be described. When a test is performed by applying VO as a set voltage of a program power supply in order to limit the maximum current flowing through the DUT 6 to IO, D / D
Digital information about the limiting current is given to the A converter 1B, and the voltage value converted into an analog value by the D / A converter 1B is output to the operational amplifier 3B.
The base voltage of the transistor 4 is controlled by the output of B, whereby the current IA flows from the terminal A, which is a current limiting terminal, to the terminal B, which is a negative power supply voltage, via the resistor 2C.

When the analog information of the voltage VO applied to the DUT 6 is input to the D / A converter 1A, the D / A
The output voltage of converter 1A rises from 0V to set voltage VO. Assuming that the output voltage of the D / A converter 1A at this time is VD, as shown in FIG.
Outputs a low-level control signal to the switch 9 to turn off the switch 9 during a time T1 until the output voltage of the D / A converter 1A reaches 0 to VD.

As a result, the diode 8 is biased in the forward direction, and a current IB flows from the diode 8 via the resistor 2D toward the negative power supply voltage terminal B.
As a result, during T1, the current flowing from the terminal A, which is the current limiting terminal of the operational amplifier 3A, to the terminal B, which is the negative power supply voltage, is IA + IB. If the current amplification factor of the operational amplifier 3A is G, the output current IO is G * IB is larger than the original limited current, and the capacitor 5 can be charged more quickly. Therefore, the voltage can be raised to the set voltage VO to be applied to the DUT 6 earlier.

Next, when the output voltage of the D / A converter 1A reaches the set voltage VD, the voltage monitor 7 outputs a high-level control signal to the switch 9 to turn on the switch 9. As a result, one end of the resistor 2E is grounded, and the voltage at the terminal A, which is a current limiting terminal of the cathode terminal of the diode 8, is obtained by dividing the voltage by the resistance ratio between the resistor 2D and the resistor 2E, and the negative power supply voltage. If the voltage is higher than the voltage of the B terminal, the diode 8 is reverse-biased and turned off.
Then, a current IC flows from the ground point to the terminal B, which is a negative power supply voltage, via the switch 9, the resistor 2E, and the resistor 2D.

As a result, the current flowing from the terminal A which is the current limiting terminal of the operational amplifier 3A is only the preset current IA, and the output current IO is limited to the set value. In this way, the output current is increased only until the voltage of the program power supply rises, the time for charging the capacitor 5 connected to the DUT 6 is shortened, and the set voltage can be applied to the DUT 6 at high speed.

As described above, the current limiting circuit 10 according to the present embodiment differs from the conventional current limiting circuit 20 in that
By adding the resistors 2D and 2E, the voltage monitor 7, the diode 8, and the switch 9, the operational amplifier 3A
The value of the current flowing from the A terminal, which is the current limiting terminal, is controlled. For this reason, the output current limit is set to a value larger than the set value until the program power supply rises from 0 V to the set voltage VO, and when the program power supply voltage reaches the set value, the output current limit is set to the original set value. Can be.

Therefore, the current setting circuit 10 in the present embodiment can apply the test setting voltage VO to the DUT 6 as the sample to be measured at high speed.
The test time of the sample to be measured can be reduced, and when the voltage applied to the DUT 6 reaches the set voltage VO, the set current IO input to the DUT 6 can be limited to a predetermined value.

In this embodiment, in order to increase the current flowing for limiting the current of the operational amplifier 3A,
Although the resistors 2D and 2E, the voltage monitor 7, the diode 8, and the switch 9 are added to the conventional current limiting circuit 20, this current can be increased only while the capacitor 5 is being charged. Any circuit may be used as long as it has a circuit configuration.

[0042]

According to the current limiting device of the present invention, the power supply voltage can be applied to the sample to be measured at high speed, and the test time of the sample to be measured can be shortened as a whole test.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main configuration of a current limiting circuit according to an embodiment of the present invention;

FIG. 2 is a diagram showing output states of a D / A converter 1A and a voltage monitor 7 of a current limiting circuit 10 according to one embodiment to which the present invention is applied.

FIG. 3 is a diagram showing a main configuration of a conventional current limiting circuit 20.

[Explanation of symbols]

REFERENCE SIGNS LIST 1A, 1B D / A converter 2A, 2B, 2C, 2D, 2E Resistor 3A, 3B Operational amplifier 4 Transistor 5 Capacitor 6 Sample to be measured 7 Voltage monitor 8 Diode 9 Switch 10 Current limiting circuit of the present invention 20 Conventional current Limiting circuit

Claims (5)

[Claims] 1. A power signal output means for outputting a voltage signal for supplying power to a sample to be measured, an amplification means for amplifying a voltage signal output by the power signal output means, and an amplification by the signal amplification means A current limiting circuit comprising: a power supply fluctuation absorbing unit configured to absorb a fluctuation in a power supply supplied to the sample to be measured by the applied voltage signal; and an amplification factor setting unit configured to set an amplification factor in the signal amplification unit. Power supply voltage monitoring means for monitoring the voltage level of the voltage signal output by the signal output means; and gain changing means for changing the setting of the gain of the gain setting means based on the monitoring result of the power supply voltage monitoring means. And a current limiting circuit comprising: 2. The amplification factor setting means, wherein the power supply voltage monitoring means detects the amplification factor setting when the voltage level of the voltage signal output from the power supply signal output means has reached a predetermined voltage value. 2. The current limiting circuit according to claim 1, wherein the setting of the amplification factor of the means is reduced. 3. The amplification factor changing means includes a diode and a switch, and changes the setting of the amplification factor of the amplification factor setting means by ON / OFF-controlling the switch. Or the current limiting circuit according to claim 2. 4. The power supply signal output means includes a D / A converter for converting a digital signal into an analog voltage signal, and the amplifying means includes an inverting amplifier circuit connected to an output of the D / A converter. The power supply fluctuation absorbing means is a capacitor connected to the sample to be measured and absorbing power supply fluctuations of the sample to be measured, and the amplification factor setting means converts the arbitrarily set output current limit information to a voltage value. D / A to convert and output
A converter, connected to an output of the D / A converter and connected to a first operational amplifier current limiting terminal constituting the inverting amplifier circuit, for controlling a base voltage of a transistor for flowing a constant current; A second operational amplifier, wherein the amplification factor changing means is connected in parallel between the emitter and the collector of the transistor, connects an anode terminal to a current control terminal of the first operational amplifier, and connects a cathode terminal to a resistor. 4. The current limiting circuit according to claim 3, further comprising: a diode connected to a negative power supply voltage terminal via the switch; and a switch connected to a cathode terminal of the diode and having the other end grounded. 5. The power supply voltage monitoring means switches off the power supply until the voltage applied to the sample to be measured reaches a set voltage value, and switches the diode and the resistor from the current control terminal of the first operational amplifier. The current flowing from the current control terminal of the first operational amplifier set in advance is increased by flowing a current to the negative power supply voltage terminal through the device, thereby increasing the input current flowing into the sample to be measured. When the voltage applied to the sample to be measured reaches a set voltage value, a switch is turned on by the power supply voltage monitoring means,
A reverse voltage is applied to the diode to return the current flowing from the current control terminal of the first operational amplifier to a predetermined value, and the maximum value of the output current of the first operational amplifier only while charging the capacitor 5. The current limiting circuit according to claim 4, wherein the power supply voltage applied to the sample to be measured is increased at a high speed.