JP4581865B2 - Voltage application device - Google Patents

Description

  The present invention is used in, for example, an IC tester, and in a voltage application device that controls an output voltage based on a difference voltage between a set voltage and a feedback output voltage, a voltage that can create a voltage waveform that rises substantially linearly and rises The present invention relates to an applying device.

  The IC tester, for example, gives an input pattern to an object to be tested (hereinafter abbreviated as DUT) such as a memory IC, compares the output from the DUT with an expected value pattern, and determines the quality of the DUT. The IC tester is required to perform a test under the same conditions as the actual use state of the DUT. In recent years, memory ICs are increasingly used when the rise time of the power supply voltage is as slow as several tens of milliseconds. For this reason, voltage adjustment with a slower rise time than before has been required. Hereinafter, a description will be given with reference to FIG.

  In FIG. 5, the power supply unit 10 supplies a predetermined voltage to the DUT 20. And the power supply unit 10 is comprised by the following. The digital / analog converter 11 applies a set voltage. The resistor 12 has one end connected to the output end of the digital / analog converter 11. The resistor 13 has one end connected to the other end of the resistor 12. The differential amplifier 14 has an inverting input terminal connected to the other end of the resistor 12 and a non-inverting input terminal grounded. The variable capacitor 15 has one end connected to the non-inverting input terminal of the differential amplifier 14 and the other end connected to the output end of the differential amplifier 14. The resistor 13 and the variable capacitor 15 constitute a time constant circuit. By changing the capacitance of the variable capacitor 13, this time constant can be changed. When the resistance value of the resistor 13 is R and the capacitance of the capacitor 15 is C, the time constant τ = R × C. The current measurement resistor 16 has one end connected to the output end of the differential amplifier 14 and the DUT 20 connected to the other end. The diodes 17 and 18 are connected in parallel to the current measurement resistor 16 in opposite directions. Then, the current measurement is performed by a device (not shown) using the current measurement resistor 16. The buffer amplifier 19 has an input end connected to the other end of the current measuring resistor 16 and an output end connected to the other end of the resistor 13.

  The operation of such an apparatus will be described below. FIG. 6 shows an output voltage waveform of the power supply unit 10 shown in FIG. 6A shows a waveform (−Vdac) obtained by reversing the polarity of the output waveform of the digital / analog converter 11, FIG. 6B shows a voltage waveform (Vdut) applied to the DUT 20, and the vertical axis indicates the voltage value. The horizontal axis is time. The output of the digital / analog converter 11 rises immediately, but the waveform applied to the DUT 20 rises with a delay due to the time constant circuit of the resistor 13 and the variable capacitor 15. Further, by adjusting the variable capacitor 15, the rise time can be changed from t1 to t2.

Japanese Patent Laid-Open No. 2002-286808

  However, such a power supply unit 10 has the following problems.

  The power supply unit 10 shown in FIG. 5 can adjust the slew rate of the voltage supplied to the DUT 20 by adjusting the variable capacitor 15. However, since the voltage varies exponentially due to the characteristics of the circuit, a voltage waveform that rises linearly cannot be created. The characteristics of the memory IC when the power supply voltage is applied require a waveform that rises linearly, but there is a problem that this requirement cannot be satisfied.

  Accordingly, an object of the present invention is to provide a voltage application device capable of creating a voltage waveform that rises substantially linearly.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In the voltage application device that controls the output voltage that the IC tester gives as the power supply voltage of the memory IC to be tested based on the difference voltage between the set voltage and the output voltage that is fed back,
A digital / analog converter that outputs a stepped voltage that changes by a predetermined step voltage width at a constant step time;
A time constant circuit arranged in either the output path of the digital / analog converter or the feedback path of the output voltage, and the output of the digital / analog converter changes stepwise during the step time. The time when the voltage supplied to the memory IC is almost 100% is set .
According to a second aspect of the invention, an invention of claim 1,
The slew rate of the output voltage is changed by changing the step voltage width.
Invention of Claim 3 is invention of Claim 1 or 2, Comprising:
In the time constant circuit, at least two different time constants can be switched, and the step time is changed for each different time constant.
Invention of Claim 4 is invention in any one of Claims 1-3 , Comprising:
The time constant circuit is composed of a resistor and a capacitor.
The invention according to claim 5
In the voltage application device that controls the output voltage that the IC tester gives as the power supply voltage of the memory IC to be tested based on the difference voltage between the set voltage and the output voltage that is fed back,
A digital / analog converter that outputs a stepped voltage that changes by a predetermined step voltage width at a constant step time;
A voltage dividing resistor that outputs a difference voltage between the set voltage output by the digital / analog converter and the output voltage;
A differential amplifier that inputs the differential voltage of the voltage dividing resistor to the inverting input terminal, grounds the non-inverting input terminal, and outputs the output voltage;
A capacitor provided between an inverting input terminal and an output terminal of the differential amplifier is provided , and the step time is supplied to the memory IC when the output of the digital / analog converter changes stepwise. is characterized in that that voltage is set the time becomes almost 100%.

As is apparent from the above description, the present invention has the following effects.
Based on the difference between the voltage set voltage and the feedback output voltage, the voltage application device for controlling the output voltage, the output of the digital / analog converter for outputting a waveform that changes stepwise with a constant step time, the digital / A high-frequency component is removed by a time constant circuit provided in the output path of the analog converter or the feedback path of the output voltage.

  By shortening the fixed step time and increasing the number of steps, it is possible to supply a waveform that increases approximately linearly. Further, the slew rate can be easily changed by changing the step voltage.

  In addition, since the time constant of the time constant circuit can be switched to at least two stages, a voltage waveform that rises almost linearly in a wide range can be created.

In addition, the digital / analog converter outputs a voltage that changes stepwise in a fixed step time, and the output voltage is output by removing the high frequency component with the time constant circuit of the voltage dividing resistor and capacitor. A voltage waveform that increases linearly can be output.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a voltage applying device according to the present invention. Note that the same reference numerals are given to the same elements as those in FIG.

  In FIG. 1, a voltage supply unit 30 is a voltage application device and supplies a predetermined voltage to the DUT 20 with substantially the same configuration as the current supply unit 10. The switch 31 has one end connected to the inverting input terminal of the differential amplifier 14. The capacitor 32 is provided in place of the variable capacitor 15, and has one end connected to the other end of the switch 31 and the other end connected to the output end of the differential amplifier 14. The resistor 13 and the capacitor 32 constitute a time constant circuit.

  The operation of such an apparatus will be described below. When supplying a power supply voltage that rises substantially linearly to the DUT 20, the switch 31 is set to ON. In the following description, it is assumed that the switch 31 is on. The digital / analog converter 11 outputs a stepped voltage waveform that increases at a constant rate (for example, 5 mV) every predetermined step time (for example, 10 μS) by a control unit (not shown). This step time is set to a time when the voltage supplied to the DUT 20 becomes almost 100% when the output of the digital / analog converter 11 changes in a stepped manner.

  This will be described with reference to FIG. FIG. 2 shows an output waveform of the digital / analog converter 11 and a voltage waveform supplied to the DUT 20. A dotted waveform 41 in the figure is an output of the digital / analog converter 11, and a solid waveform 42 is a waveform of a power supply voltage supplied to the DUT 20. The resistance values of the resistors 12 and 13 are the same, and the waveform 41 is displayed with the polarity reversed.

  FIG. 2A shows an example of a waveform when the slew rate is 500 V / sec (change from 0 V to 5 V at 10 mS). As shown in the waveform 41, the digital / analog converter 11 generates a step-like waveform that increases by 5 mV every 10 μS. This waveform has a high-frequency component removed by a time constant circuit. Since the time constant is set so as to catch up with the output of the digital / analog converter 11 at 10 μS, the power supply voltage (waveform 42) supplied to the DUT 20 does not become stepped. Although the middle is omitted in the figure, since the number of steps is 1000 (= 5 V / 5 mV), good linearity can be obtained.

  FIG. 2B shows an example when the slew rate is 250 V / sec. The step time is fixed to 10 μS, and the step voltage output from the digital / analog converter 11 is set to 2.5 mV. Also in this case, the power supply voltage supplied to the DUT 20 catches up with the output of the digital / analog converter 11 at 10 μS, so that it does not change stepwise and good linearity can be obtained. Note that the number of steps is 2000 (= 5 V / 2.5 mV).

  FIG. 2C shows a case where the step voltage output from the digital / analog converter 11 is set to 2.5 mV as in (B) and the step time is set to 20 μs in order to obtain a slew rate of 125 V / sec. It is an example. Since the power supply voltage supplied to the DUT 20 becomes almost stable at 10 μS, a flat portion 43 is generated in the waveform 42 and good linearity cannot be obtained. On the other hand, if the step time is shorter than 10 μS, the output of the digital / analog converter 11 changes before the power supply voltage supplied to the DUT 20 is stabilized, so that good linearity cannot be obtained.

  When the slew rate adjustment is not performed, the switch 31 is turned off, a control unit (not shown) gives a set value to the digital / analog converter 11, and the power supply unit 30 supplies power to the DUT 20 with no slew rate adjustment. give.

  In this way, in order to obtain voltage waveforms with different slew rates, the step time output by the digital / analog converter 11 is fixed and the width of the voltage step is changed. In this way, the power supply voltage supplied to the DUT 20 does not have a flat portion or a sudden change portion, and a voltage waveform that rises substantially linearly can be created. Also, a waveform having an amplitude other than 5V can be output by appropriately changing the voltage step width.

  In the embodiment shown in FIG. 1, a capacitor 32 is inserted in the feedback loop of the differential amplifier 14 and a time constant circuit is formed with the resistor 13, but this time constant circuit may be arranged in another part. Such an embodiment is shown in FIG. Note that the same reference numerals are given to the same elements as those in FIG.

  In FIG. 3, a voltage supply unit 50 is a voltage application device and supplies a predetermined voltage to the DUT 20 with substantially the same configuration as the current supply unit 10. The resistor 51 has one end connected to the output end of the digital / analog converter 11. The switch 52 has one end connected to the other end of the resistor 51. The capacitor 53 is provided instead of the variable capacitor 15, one end is connected to the other end of the switch 52, and the other end is grounded. The buffer 54 connects the other end of the resistor 51 to the input end, and connects the output end to one end of the resistor 12.

  In this embodiment, a resistor 51 and a capacitor 53 form a time constant circuit, and this time constant circuit is inserted on the output side of the digital / analog converter 11. The insertion position of the time constant circuit is not limited to this position, and may be arranged anywhere on the output side of the digital / analog converter 11 or the feedback loop from the DUT 20. For example, it can be arranged on the output side of the buffer 54, the input / output side of the buffer 19, and the input / output side of the amplifier 14.

  When trying to output a waveform with a small slew rate, that is, a waveform with a slow rise, the step voltage may be less than the resolution of the digital / analog converter 11. In such a case, the capacitance of the capacitors 32 and 53 may be increased to increase the time constant, that is, the step time. However, this time, the number of steps when outputting a waveform having a large slew rate, that is, a waveform having a fast rise time. Decreases and linearity deteriorates.

  Therefore, the time constant can be switched and switched as appropriate. This embodiment is shown in FIG. In addition, the same code | symbol is attached | subjected to the same element as FIG. 1, and description is abbreviate | omitted.

  In FIG. 4, a voltage supply unit 60 is a voltage application device and supplies a predetermined voltage to the DUT 20 with substantially the same configuration as the current supply unit 30. The switch 61 is provided instead of the switch 31 and connects the movable contact a to the inverting input terminal of the differential amplifier 14. The capacitor 62 is provided in place of the capacitor 32 and has one end connected to the fixed contact c of the switch 61 and the other end connected to the output end of the differential amplifier 14. The capacitor 63 has one end connected to the fixed contact d of the switch 61 and the other end connected to the output end of the differential amplifier 14. The resistor 13 and the capacitors 62 and 63 constitute a time constant circuit. For example, the capacitance of the capacitor 62 is doubled that of the capacitor 63, and when the step time is 10 μS, the capacitor 63 is selected by the switch 61, and when the step time is 20 μS, the capacitor 62 is selected.

  The operation of such an apparatus will be described below. A case where the power supply voltage is applied to the DUT 20 by changing the set voltage to 1.25 to 5 V at a rise time of 10 ms will be described.

  Using a D / A converter with a resolution of 2.5 mV, when the set voltage is 1.25 to 2.5 V, the movable contact a of the switch 61 is connected to the fixed contact c, and the capacitor 62 is selected. Then, a control unit (not shown) causes the digital / analog converter 11 to output a stepped waveform with a step time of 20 μS, up to 500 steps, and a step voltage of 2.5 or 5 mV. Here, when the set voltage is 2 V, 2 V is output by combining 2.5 mV and 5 mV step voltages to match the number of steps 500. As a result, even if the set voltage is low, the number of steps can be ensured and the light can rise almost linearly.

  When the set voltage is 2.5 to 5 V, the movable contact a of the switch 61 is connected to the fixed contact d, and the capacitor 63 is selected. Then, a control unit (not shown) causes the digital / analog converter 11 to output a stepped waveform at a step time of 10 μS, up to 1000 steps and a step voltage of 2.5 or 5 mV. Similarly, when the set voltage is 4V, the step voltage of 2.5 mV and 5 mV are combined to output 4V in order to match the number of steps of 1000. As a result, even when the set voltage is high, it can be raised almost linearly.

  When the slew rate is not adjusted, the movable contact a of the switch 61 is connected to the fixed contact b. A control unit (not shown) gives a set value to the digital / analog converter 11, and the power supply unit 60 supplies an output voltage of the set value to the DUT 20.

  In these embodiments, a circuit using a resistor and a capacitor is used as the time constant circuit, but other configurations may be used. In short, any configuration that removes the high-frequency component of the voltage signal that changes stepwise and converts it into a smooth waveform may be used.

  Further, although the digital / analog converter 11 is used as means for generating a stepped voltage, the digital / analog converter is not necessarily required. In short, any voltage generator may be used as long as it can generate a stepped waveform having a predetermined step voltage in a fixed step time and can change the step voltage.

  Further, the current measuring resistor 16 and the diodes 17 and 18 are not necessary unless current measurement is performed.

  Moreover, although the structure which provided the switches 31 and 61 was shown, the structure without the switches 31 and 61 may be sufficient. In this case, the slew rate adjustment is always performed.

  Further, the power supply units 30, 50 and 60 have been shown to be provided to the DUT 20. However, the present invention is not limited to this, and any device that requires a slew rate adjusted voltage may be used. Good.

  Further, the capacitor 32 may be variable to change the time constant.

It is a block diagram which shows one Example of this invention. It is a figure which shows the characteristic of the apparatus shown in FIG. It is a block diagram which shows the 2nd Example of this invention. It is a block diagram which shows the 3rd Example of this invention. It is a block diagram of the conventional power supply unit. It is a figure which shows the characteristic of the apparatus shown in FIG.

Explanation of symbols

30, 50, 60 Power supply unit 11 Digital / analog converter 12, 13, 51 Resistor 14 Differential amplifier 19, 54 Buffer 20 DUT
31, 52, 61 Switch 32, 53, 62, 63 Capacitor

Claims (5)

In the voltage application device that controls the output voltage that the IC tester gives as the power supply voltage of the memory IC to be tested based on the difference voltage between the set voltage and the output voltage that is fed back,
A digital / analog converter that outputs a stepped voltage that changes by a predetermined step voltage width at a constant step time;
A time constant circuit arranged in either the output path of the digital / analog converter or the feedback path of the output voltage, and the output of the digital / analog converter changes stepwise during the step time. In this case, a time for setting the voltage supplied to the memory IC to approximately 100% is set . Wherein by changing the step voltage range, the voltage applying device according to claim 1, characterized in that so as to vary the slew rate of the output voltage. 3. The voltage application device according to claim 1, wherein the time constant circuit is configured to switch at least two different time constants, and the step time is changed for each different time constant. . The time constant circuit includes a resistor and a voltage applying device according to any one of claims 1 to 3, characterized in that it is a capacitor. In the voltage application device that controls the output voltage that the IC tester gives as the power supply voltage of the memory IC to be tested based on the difference voltage between the set voltage and the output voltage that is fed back,
A digital / analog converter that outputs a stepped voltage that changes by a predetermined step voltage width at a constant step time;
A voltage dividing resistor that outputs a difference voltage between the set voltage output by the digital / analog converter and the output voltage;
A differential amplifier that inputs the differential voltage of the voltage dividing resistor to the inverting input terminal, grounds the non-inverting input terminal, and outputs the output voltage;
A capacitor provided between an inverting input terminal and an output terminal of the differential amplifier is provided , and the step time is supplied to the memory IC when the output of the digital / analog converter changes stepwise. A voltage application device characterized in that a time for which the voltage to be obtained is almost 100% is set .

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