JPH0782065B2 - Power supply circuit for IC tester measurement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention prevents the current clamp region from being reached even when a transient current larger than the full scale of the measurement range flows when measuring the DUT current. With time control,
The present invention relates to a power supply circuit for measurement of an IC tester, which enables the current measurement with high accuracy in a target range and further performs the contradictory operation of clamping with an arbitrary current.

[Prior Art] Next, a configuration diagram according to the prior art will be described with reference to FIG.

In FIG. 6, 1 is a D / A converter, 2 and 3 are resistors, 4 and 5 are operational amplifiers, 6 is a current limiter circuit, 7 is a range over detection circuit, 8 is a resistor, 9 is a current detection circuit, and 10 is An A / D converter, 11 is a DUT, and 12 is a test pattern generator.

Resistors 2 and 3 are voltage setting range resistors that determine the applied voltage V ₀ to the DUT 11, resistor 8 is a current measuring range resistor, voltage V _i is the output of the D / A converter 1, and voltage V _c is the current. The output of the detection circuit 9, the current i _0, is the current flowing through the DUT 11.

The signals P and N, which are the outputs of the range over detection circuit 7, inform that there is an overcurrent, and indicate that the current i ₀ is flowing, that is, the force current is over or the sink current is over.

Next, the current limiter circuit 6 will be described with reference to FIG.

In FIG. 8, 61 is a constant current source, 62 and 63 are transistors, and 64 to 66.
Is resistance.

The current of the constant current source 61 is I _S , the base-emitter voltage of the transistor 62 is V _BE , and the resistance values of the resistors 64 to 66 are R1 and R, respectively.
2, assuming that the current flowing through R3 and the resistor 66 is I _E , the following equation holds from FIG.

V _BE = I _E × R ₁ × R ₃ / (R ₁ + R ₂ ) …… (1) When I _E such that the voltage V _BE becomes about 0.6 V, the transistor 6
2 is turned on and the current is clamped.

The base current I _B of the transistor 63 at that time is determined so as to satisfy the following equations (2) and (3).

I _E = I _B × h _fe1 (2) I _S = I _C + I _B (3) where I _C is the collector current of the transistor 62 and h _fe1 is the DC current amplification factor of the transistor 63.

Therefore, limiting the current I _B by controlling the value of the current I _S , shunting the current I _C , or controlling the voltage V _{BE of the} transistor 62 limits the current I _E. You can

Next, an example of a circuit for controlling the current limiter circuit 6 of FIG. 8 with the P signal will be described with reference to FIG.

FIG. 9 shows only a main part of FIG. 8, and a transistor 67 is added to FIG.

The transistor 67 operates equivalently to the transistor 62.

When the signal P is applied to the base of the transistor 67, the constant current I _S is shunted to the transistor 67 and the current I _E flowing through the resistor 66 is limited.

Regarding the signal N for controlling the sink current over,
Since it is a complementary circuit as shown in the figure,
PNP that operates the same as transistor 67 in the circuit on the sink side
A transistor can be connected to limit the current I _B.

The current limiter circuit 6 operates by the signal P and the signal N, and the current is clamped.

The voltage V ₀ applied to the DUT 11 is V ₀ = −R _B / R _A × V _i (4), and the voltage V ₀ changes the voltage V _i or the resistance value R _{A of} the resistor 2 It can be changed by switching the ratio of the resistance value R _B of 3 with an electronic switch or the like.

A resistor 8 is commonly connected to the input terminals of the overrange detection circuit 7 and the current detection circuit 9.

The currents flowing through the respective input terminals of the range over detection circuit 7 and the current detection circuit 9 have a high input impedance so that they can be ignored with _respect to the current i ₀ . Furthermore, the current to the + terminal of the operational amplifier 4 can be ignored.

Therefore, since the current i ₀ flowing through the DUT 11 and the current flowing through the resistor 8 are equal, the voltage i ₀ × R _m of the resistor 8 may be measured to measure the current i ₀ flowing through the DUT 11.

The current detection circuit 9 converts the voltage of i ₀ × R _m so that it falls within the full scale of the A / D converter 10. That is, the output voltage V _c of the current detection circuit _{9, V c = K × i 0} × R m ...... (5) Here, K = range with an amplification factor R _m = known value resistor the voltage V _C The current i ₀ can be known by A / D conversion. At this time, when it resistance R _m of the resistor 8 is only one kind, since the over-scale depending on the value of the current i _0, so as to measure the current i ₀ extensive resistance R _m of the resistor 8 relays Or prepare multiple range resistors so that they can be switched by using electronic switches.

Further, when the range over detection circuit 7 selects and measures a certain range resistance R _m , the current i ₀ exceeding the full scale of the range, that is, from the equation (5), i ₀ = V _c / (K × R _m ) When more than the indicated current flows, the signal P or the signal N is output as the range over signal to operate the current limiter circuit 6 to limit the current.

[Problems to be Solved by the Invention] According to FIG. 6, the static DC current of the DUT 11 can be measured. However, in tests such as memory IC,
With the pulse signal from the pattern generator 12 applied to the other terminal of the DUT 11, the current of the DUT 11 is measured.

When the DUT11 is CMOS or the like, a rapid current change occurs at the change point of the test pattern, and a pulsed transient current several times as large as that of the target measurement lens flows.

Next, the transient current waveform diagram of FIG. 6 will be described with reference to FIG.

FIG. 7 is an enlarged diagram of the change of the current i ₀ on the time axis.

In the case of the measurement current i _{m in} FIG. 7, it is within the measurement range 21, so the measurement range 21 is selected for measurement. However, since the transient current i ₀ exceeds the range of the range 21, the current in the shaded area is clamped by the current limiter circuit 6 in FIG. 6, and the necessary current cannot be supplied to the DUT 11.

On the contrary, when the measurement range 22 that can cover the transient current value is selected and measured, a low level is measured in the large measurement range 22, and there is a problem that the measurement cannot be performed accurately.

Further, the current limiter circuit 6 operates only when the range over detection circuit 7 operates, that is, when the current i ₀ exceeding the measurement range flows, and any current within the measurement range flows. However, there is a problem in that it is not possible to meet the request to enter the current limiting operation.

It is an object of the present invention to provide a measuring power supply circuit for an IC tester that measures accurately in a target measurement range by preventing a clamped operation area from entering even if a pulsed transient current that exceeds the measurement range flows. .

In addition, even if it is within the measurement range, the DUT11
It is an object of the present invention to provide a circuit which solves both contradictory requirements of limiting the current flowing through the circuit.

[Means for Solving the Problem] In order to achieve this object, according to the present invention, a current limiter circuit 6 for limiting an output current of a power supply, and a resistor 8 connected in series to an output of the current limiter circuit 6 are provided. , A current detection circuit 9 for detecting the current flowing through the resistor 8 and converting it into a voltage
And an incomplete integrator 14 for averaging the output voltage of the current detection circuit 9, a switch 13 for switching and extracting the input voltage or the output voltage of the incomplete integrator 14, and an A / which connects the output of the switch 13 D converter 10, a first comparator 15 for the output voltage of the incomplete integrator 14 compared with the first reference voltage P _ret, second reference voltage first reference voltage P _ref and polarity is reversed A second comparator 16 for comparing the output voltage of the incomplete integrator 14 with N _ref , and adding a current flowing in the resistor 8 to the DUT 11
The output signal P of 5 and the output signal N of the second comparator 16 control the current limiter circuit 6.

Next, a configuration diagram of the measuring power supply circuit of the IC tester according to the present invention will be described with reference to FIG.

In FIG. 1, 13 is a switcher, 14 is an incomplete integrator having a programmable integral time constant, 15 and 16 are comparators, 17 is an inverting amplifier, 18
Is a D / A converter, and other parts are the same as those in FIG.

That is, FIG. 1 shows the range over detection circuit 7 taken from FIG. 6, and the switch 13 to D / A converter 18 is added to FIG.

The output of the current detection circuit 9 enters the incomplete integrator 14, and the output of the incomplete integrator 14 enters the comparators 15 and 16.

Further, the switching device 13 switches and extracts the input voltage or the output voltage of the incomplete integrator 14, and the output of the switching device 13 is connected to the A / D converter 10.

The output of the D / A converter 18 becomes the reference voltage of the comparators 15 and 16,
It is supplied to the comparator 16 via an inverting amplifier 17.

The output of the comparator 15 is applied to the current limiter circuit 6 as a signal P, and the output of the comparator 16 is applied to the current limiter circuit 6 as a signal N.

[Operation] Next, the operation of the incomplete integrator 14 will be described with reference to FIGS. 2 and 3.

FIG. 2 shows an example of an RC integrating circuit, which shows the output voltage V _j when the input voltage is V _c .

FIG. 3 is a charging / discharging waveform diagram of FIG. 2. When CR is small, the curve 19 is obtained, and when CR is large, the curve 20 is obtained.

Incomplete integrator when the voltage V _c is integrated by the incomplete integrator 14.
The output voltage V _{j of} 14 changes as shown in FIGS. 2 and 3, and has the waveform of the voltage V _j in FIG.

The incomplete integrator 14 has the transfer function of the first-order lag system, and the second
It is equivalent to the CR circuit shown in the figure. The output response V _j when a pulsed voltage V _c proportional to the current i ₀ to be measured is input to the input of FIG. 2 changes as shown in FIG.

When charging the input voltage V _C to C _{is, V j = V C (1} -ε -t / CR) ...... (6) Further, when it is _{discharged, V j = V C · ε} - ^{t / CR} (7), which is represented by the well-known charge / discharge method.

Here, within the period T in which the voltage V _{c of} FIG. 3 exists, the voltage V _j
The time constant CR is selected so that does not reach the maximum value of the voltage V _c .

That is, CR is determined from the equation (6) or the equation (7) with V _j / V _c <1, t = T, and as shown in FIG.
Integrate to be within.

Each of the comparators 15 and 16 has a direction in which the current i ₀ flows, that is,
It operates for over detection of force current flowing into DUT11 and sink current drawing from DUT11.

Reference voltage P _ref of comparator 15 and reference voltage N of comparator 16
_ref is supplied from the D / A converter 18 and is set to a value equal to or less than the full scale of the current measurement range. The reference voltage N _ref of the comparator 16 has a value inverted from the polarity of the reference voltage P _ref in the inverting amplifier 17.

The output voltage of the comparator 15 is the signal P and the current limiter circuit 6
In addition, the output voltage of the comparator 16 is applied to the current limiter circuit 6 as a signal N.

The output voltage V _c of the current detection circuit 9 is proportional to the current i ₀ measured by the relationship of the equation (5), and has the waveform of the voltage V _c shown in FIG.

The waveform of the voltage V _c shows the case where the direction of the current i ₀ is the forcing current flowing into the DUT 11, which is the same as the current i _{0 in} FIG. 7, and can be read as the current i ₀ .

The voltage V _j is controlled by the time constant CR so that it falls within the measurement range 23, and does not reach the preset reference voltage _Pref of the comparator 15, that is, the level 24 in FIG. Therefore, the comparators 15 and 16 do not operate and the overrange signal P and signal N do not appear, so the current limiter circuit 6 also does not operate and the necessary current can be supplied to the DUT 11.

4th As Figure, even if the pulse current that exceeds the measurement range 23 flows, without switching to an optimum range to the measured current level i _m from range higher that the current can be supplied,
From the beginning, it is possible to measure accurately in the target range. At this time, the switch 13 is set to the terminal a side and the voltage V _c
Connect to A / D converter 10.

For sink current measurement with different current directions, voltage V _c and voltage
The polarity of V _j is inverted, and the comparator 16 operates similarly.

Next, there are times when it is desired to limit the current that flows into or sinks into the DUT11 at an arbitrary current value within the measurement range.In such a case, the reference voltage P _ref of the comparator 15 or the reference voltage N _ref of the comparator 16 is set to the first value. By lowering the level 24 to the level 25 in FIG. 4, the shaded portion of the voltage V _j can be detected as an over region and the current can be limited.

Further, according to the circuit of FIG. 1, the average current including the pulse current as shown in FIG. 5 can be measured. When the pulse current i ₀ as shown in FIG. 5 flows, the voltage after the elapse of T ₁ of the voltage output V _j when the incomplete integrator 14 charges the pulse current is
e _c or e voltage after T ₂ has elapsed at the time of discharging from the _c e _d,, if the ripple voltage is e _r, from equation _{(6), e c = e} d (1-ε -T1 / CR) ...... (8) from (7), the relationship ^{_{e d = e c · ε -T1}} / CR ...... (9) is obtained, the ripple voltage e _{r is, e r = e c -e d} ...... (10) Then, the integration time constant CR of the incomplete integrator 14 is determined by the ripple voltage of the average current that allows the duration of the pulse current, the switch 13 is switched to the terminal b side, and the output voltage V _j of the incomplete integrator 14 is determined. Is connected to the A / D converter 10, the average of the current i ₀ can be measured.

Further, set in the D / A converter 18 to a level of different larger polar than the integrated output V _j of the reference voltage N _ref is incomplete integrator 14 of the comparator 16 with the reference voltage P _ref of the comparator 15 of FIG. 1 .

In such a state, the comparators 15 and 16 do not operate, and the signals P and N for driving the current limiter circuit 6 are not output.

According to the present invention, when the load current is measured, the current clamp is not applied even if a pulsed transient current that is several times the current to be measured or exceeds the measurement range flows. Further, it is possible to perform accurate measurement by using the optimum range for the level of the measurement current without changing the measurement range.

On the contrary, the current can be clamped so that the current does not flow into the load more than an arbitrary current within the measurement range, and the load current can be limited.

Further, the average value of pulse current can be measured.

[Brief description of drawings]

FIG. 1 is a current supply circuit for measurement of an IC tester according to the present invention, FIGS. 2 and 3 are operation explanatory diagrams of the incomplete integrator 14 of FIG. 1, and FIGS. 4 and 5 are of FIG. FIG. 6 is a waveform diagram for explaining the operation, FIG. 6 is a configuration diagram according to the prior art, FIG. 7 is a waveform diagram of the transient current of FIG. 6, FIG. 8 is an operation explanatory diagram of the current limiter circuit 6, and FIG. 9 is FIG. It is a figure which shows an example of the circuit which controls the current limiter circuit 6 of this with a P signal. 1 ... D / A converter, 2 ... resistor, 3 ... resistor, 4 ... operational amplifier, 5 ... operational amplifier, 6 ... current limiter circuit, 7 ... overrange detection circuit, 8 ... resistor , 9 ...
… Current detection circuit, 10 …… A / D converter, 11 …… DUT, 12 ……
Test pattern generator, 13-switch, 14-incomplete integrator, 15-comparator, 16-comparator, 17-inverting amplifier, 16-D / A converter.

Claims (1)

[Claims] 1. A current limiter circuit (6) for limiting an output current of a power supply, a resistor (8) connected in series to an output of the current limiter circuit (6), and a current flowing through the resistor (8) is detected. The current detection circuit (9) that converts the output voltage to a voltage, the incomplete integrator (14) that averages the output voltage of the current detection circuit (9), and the input voltage and output voltage of the incomplete integrator (14) A switcher (13) for switching and taking out, an A / D converter (10) connecting the output of the switcher (13), and a first reference voltage and an output voltage of the incomplete integrator (14) are compared. And a second comparator (16) for comparing the output voltage of the incomplete integrator (14) with a second reference voltage having a polarity opposite to that of the first reference voltage. , The current flowing through the resistor (8) is applied to the DUT (11) to output the output signal P of the first comparator (15) and the output signal N of the second comparator (16). Measuring the power supply circuit of the IC tester and controlling the current limiter circuit (6).