JP3002653B2 - IC test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC test apparatus, and more particularly to an apparatus for protecting a power supply circuit for measurement from a high voltage caused by a failure of an IC under test.

[0002]

2. Description of the Related Art An IC test apparatus includes a DC test apparatus for testing DC characteristics of each terminal of an IC. FIG. 3 shows a configuration of a conventional example of this DC test apparatus.

The DC test apparatus includes a plurality of measurement power supply circuits for applying a desired current or voltage to each terminal of the IC under test 3. The measurement power supply circuit can be mainly divided into a high voltage power supply circuit 2 for measuring leak current and a low voltage power supply circuit 1 for measuring other DC parameters.

The low-voltage power supply circuit 1 includes a VF (voltage application) DA converter 11 for supplying an input voltage to an operational amplifier 14 via an input resistor R1, an operational amplifier 14 operating as a constant voltage source or a constant current source, and A current detection resistor R ₀ for detecting a current flowing from the operational amplifier 14 to the measurement terminal of the IC 3 via the remote forcing line 17 and a voltage generated at the measurement terminal of the IC 3 in the voltage applied current measurement mode are calculated. remote sensing line 1 for feeding back via a feedback resistor R ₂ to the inverting input terminal of the amplifier 14
6, a differential amplifier 15 for extracting a voltage generated in the current detection resistor R ₀ , and an I
DA converter 12 for F (current application), DA converter 12 for IF and differential amplifier 15 in current applied voltage measurement mode
And the comparator 13 that inputs the output to the inverting input terminal of the operational amplifier 14. In the figure, an operational amplifier and an AD converter for measuring a terminal current and a terminal voltage are omitted.

In the voltage applied current measurement mode, the voltage of the terminal of the IC 3 under test is
And applied to the inverting input terminal of the operational amplifier 14 through a feedback resistor R _2, the input voltage V _in to give the VF for DA converter 11
And the terminal voltage V of the IC under test V = − (R ₂ /
R ₁₎ to maintain the V _in. The operational amplifier 14 operates as a low voltage source and applies a constant voltage to the terminal of the IC 3 under test. In this state, the differential amplifier 15 takes out the voltage generated in the current detection resistor R ₀ , supplies the output voltage to an AD converter (not shown), and compares the AD converted value with a normal value to determine the pass / fail.

In the current applied voltage measurement mode,
The output voltage of the comparator 13 is fed back to the inverting input terminal of the operational amplifier 14, and this feedback operation causes the current detection resistor R
_The voltage value generated at ₀ is maintained at a constant value, and the operational amplifier 1
4 is operated as a constant current source, and a constant current I = − (V _in / R) is continuously supplied to the terminal of the IC 3 under test. While the specified current is flowing through the terminal, the remote sensing line 16
The voltage of the terminal of the IC under test 3 is taken out through the terminal, the voltage of this terminal is supplied to an AD converter (not shown), and the AD conversion value is compared with a target value. When it is out of the range, it is judged as defective.

[0007] high-voltage power supply circuit 2 is here Yes constitutes only VF circuit for removal of the IF circuit from the low voltage power supply circuit 1, DA for VF via the input resistor R ₁₁ to the operational amplifier 22 provides an input voltage a converter 23, an operational amplifier 22 which operates as a constant voltage source, a current detecting resistor R ₁₀ for detecting a current flowing from the operational amplifier 22 via a remote forcing line 25 to the measurement terminal of the test IC3,
The voltage generated at the measurement terminal of the IC under test 3 is
Is fed back through a feedback resistor R ₁₂ to the second inverting input terminal may be configured by a remote sensing line 24 and the like. The high-voltage power supply circuit 2 may have a current application voltage measurement mode.

In the DC test shown in FIG.
The output terminal 34 of the high-voltage power supply circuit 2 is connected to the pin and the leak current is measured.
Is connected to measure other DC parameters.

During the DC test, the IC under test 3 breaks down and short-circuits between its measurement pins 2 and 7 in some cases. When the pins are short-circuited, the high voltage of the high-voltage power supply circuit 2 applied to the 7th pin is directly applied to the output terminal 30 of the low-voltage power supply circuit 1 from the 2nd pin.
In some cases, the low-voltage power supply circuit 1 was damaged beyond the allowable voltage of the low-voltage power supply circuit 1. Incidentally, since the high voltage is about ± 2 kV and the low voltage is about ± 100 V or less (1 A), the destruction is fatal and cannot be recovered.

[0010]

In the power supply circuit of the above-described conventional IC test apparatus, only the current detection resistor _R0 is provided on the output side of the operational amplifier 14, and the protection circuit is not provided for an external high voltage. Did not. For this reason, when short-circuiting occurs between the terminals of the IC under test during high-voltage and low-voltage DC measurements, internal circuit components such as operational amplifiers, differential amplifiers, and comparators that compose the low-voltage power supply circuit may be used. High voltage was applied, and it was sometimes damaged. In order to prevent this breakage, it is conceivable to increase the withstand voltage of the internal circuit components, but the circuit becomes large-scale and lacks economy.

An object of the present invention is to provide a power supply circuit with an abnormal voltage protection circuit, thereby solving the above-mentioned problems of the prior art, and preventing a power supply circuit from being damaged even if a failure occurs in an IC to be measured. An object of the present invention is to provide an IC test apparatus.

[0012]

According to the present invention, there is provided an IC test apparatus comprising a plurality of constant current sources and a constant voltage source for supplying a desired current or voltage to each terminal of an IC under test by an analog signal supplied from a DA converter. The external voltage applied to the output terminal of one power circuit and the external voltage reversely applied to the output terminal of one power circuit from the other power circuit via the terminal of the IC under test and the allowable voltage of the one power circuit are compared. An abnormal voltage detection circuit having a comparator that outputs an abnormality detection signal when the value is equal to or higher than an allowable voltage, and an external voltage is preferentially applied to the abnormal voltage detection circuit over an internal circuit configuring one power supply circuit, A delay circuit for delaying the time during which the external voltage is applied to the internal circuit forming the one power supply circuit, and an abnormality in the internal circuit forming the one power supply circuit operated by the output of the abnormality detection signal from the abnormal voltage detection circuit Electric Cut off the application is obtained a high withstand voltage, high-speed switch.

When a DC test is performed by applying a high voltage from a high-voltage power supply circuit to one terminal of an IC under test and applying a low voltage or low current from a low-voltage power supply circuit to another terminal, these voltages are applied. When a short circuit occurs between
An unacceptable high voltage is applied as an external voltage from the high voltage power supply circuit to the low voltage power supply circuit through the shorted terminal. At this time, since the delay circuit operates, the high voltage is applied to the abnormal voltage detection circuit before being applied to the internal circuit of the low voltage power supply circuit. With this application, the abnormal voltage detection circuit applies an abnormality detection signal to the high voltage / high speed switch when the high voltage exceeds the allowable voltage. This prevents the switch from operating at a high speed to apply an abnormal voltage to the internal circuit of the low-voltage power supply circuit. As a result, the low-voltage power supply circuit is protected from an abnormal voltage caused by a short circuit between the terminals.

In the above invention, it is preferable that the abnormal voltage detecting circuit is provided with a voltage dividing circuit for dividing an external voltage and applying a divided voltage, and a surge absorbing circuit for absorbing a surge voltage. If a voltage dividing circuit and a surge absorbing circuit are provided so that an external voltage or a surge voltage is not directly applied to the abnormal voltage detecting circuit, the abnormal voltage detecting circuit does not require a high withstand voltage.

In the above invention, the abnormal voltage detection circuit sets an upper limit value as a set value and outputs an abnormality detection signal when the external voltage is equal to or higher than the upper limit value. A lower limit comparator that outputs an abnormality detection signal when the voltage is equal to or lower than the lower limit value may be provided, and the outputs of the upper limit comparator and the lower limit comparator may be wired-OR connected.
Since the abnormal voltage detection circuit operates not only for the abnormal voltage exceeding the upper limit value but also for the abnormal voltage exceeding the lower limit value, the low voltage power supply circuit can be effectively protected from positive and negative abnormal voltages.

[0016]

Embodiments of the present invention will be described below. The embodiment shown in FIG. 1 is obtained by adding an abnormal voltage detection circuit 31, delay circuits 32 and 33, and high voltage / high speed switches 18 and 19 to the conventional low voltage power supply circuit 1.

The high-voltage and high-speed switches 18 and 19 are inserted in series with the remote sensing line 16 and the remote forcing line 17, respectively, and both lines 16 and 17 are opened by the output of the abnormality detection signal of the abnormal voltage detection circuit 31. Then, the application of the abnormal voltage to the internal circuit of the power supply circuit 1 is stopped. Therefore, the switches 1 on the remote sensing line 16 and the remote forcing line 17
The insertion points of 8 and 19 are on the near side of the internal circuit when viewed from the output terminal 30. For example, the power M
With the OSFET as a constituent element, the power M is adjusted so that the withstand voltage is 3 kV and the switching speed is in the order of 100 ns.
It is composed of an OSFET and its drive circuit. The power supply circuit 1
Is composed of a comparator 13, an operational amplifier 14, a differential amplifier 15, and the like.

The abnormal voltage detection circuit 31 is also connected to the near side of the internal circuit in the remote sensing line 16, but may be connected after or before the switch 18. The abnormal voltage detection circuit 31 receives an external voltage applied from the outside via the remote sensing line 16 and an allowable voltage of the low-voltage power supply circuit 1 set from the VF DA converter 11 as inputs.
A comparator 20 for applying the output to switches 18 and 19, respectively
The external voltage applied reversely to the output terminal 30 of the low-voltage power supply circuit 1 from the high-voltage power supply circuit via the terminal of the IC under test is compared with the allowable voltage of the low-voltage power supply circuit 1 to determine the absolute value of the external voltage. Outputs an abnormality detection signal when is equal to or higher than the set voltage.
The input of the comparator 20 to which an external voltage is applied is connected to low-voltage diodes D ₁ and D ₂ as a surge absorbing circuit 35 for absorbing a surge voltage, and in order to avoid direct input of a high voltage, A voltage dividing resistor R ₃ as a voltage dividing circuit 36;
Connect the R _4, the divided voltage is to be applied.
The external voltage applied to the comparator 20 may be applied from the remote forcing line 17 side.

Further, the external voltage is applied to the abnormal voltage detecting circuit 31 prior to the low-voltage power supply circuit 1 so that the external voltage is applied to the remote sensing line 16 on the inner side of the input connection point of the comparator 20 and to the remote forcing. Line 1
7, low-voltage power supply circuit 1
The voltage application to the inside is delayed. Delay circuit 32,
33 may be constituted by, for example, a CR circuit, in which case R may be used as both the feedback resistor R ₂ and the current detection resistor R ₀ .

During a test in which a high voltage is applied to one terminal of the IC under test from the high voltage power supply circuit and a low voltage is applied to the other terminal from the low voltage power supply circuit 1, a voltage is applied between the terminals to which these voltages are applied. When a short circuit occurs, an unacceptable high voltage is applied to the low-voltage power supply circuit 1. At this time, since the delay circuits 32 and 33 operate, the high voltage is applied to the abnormal voltage detection circuit 31 first. When the high voltage exceeds the allowable voltage, an abnormal voltage detection circuit 31 applies an abnormal detection signal to the high voltage / high speed switches 18 and 19. Thereby, the switches 18, 1
9 is quickly opened, and before the high voltage is applied to the internal circuit of the low-voltage power supply circuit 1, the application of the abnormal voltage to the low-voltage power supply circuit 1 is interrupted, and the low-voltage power supply circuit 1 is short-circuited between terminals. Protection from abnormal voltage caused by

In this case, an error may be further notified or the application of the high-voltage power supply circuit may be stopped using the abnormality detection signal output from the comparator 20.

As described above, according to the present embodiment, the high-voltage, high-speed switches 18 and 19 controlled to be opened and closed by the abnormal voltage detection circuit are added to the output side of the low-voltage power supply circuit so that the output voltage can be set to an allowable value. When it exceeds, the switch is opened, so that the operational amplifier 1 constituting the low-voltage power supply circuit 1 is opened.
4. Damage to components such as the differential amplifier 15 and the comparator 13 can be effectively prevented.

A voltage dividing circuit 36 for dividing an abnormal voltage and applying a low voltage having a small absolute value to the input of the comparator 20.
And a surge absorbing circuit 35 for absorbing a surge voltage, so that a divided voltage smaller than the abnormal voltage is applied to the comparator, so that the comparator is not required to have a high withstand voltage. Therefore, a general-purpose comparator can be used, which is economical.

Further, since the abnormal voltage detecting circuit 31 is operated before the internal circuit of the low voltage power supply circuit 1 by providing the delay circuits 32 and 33, it is possible to effectively prevent the low voltage power supply circuit 1 from being destroyed. .

In the above-described embodiment, since there is only one comparator for detecting an abnormal voltage, it is possible to detect only one of the positive and negative abnormal voltages. Cannot be detected. Therefore,
FIG. 2 shows a configuration in which two comparators are used so that positive and negative abnormal voltages can be detected.

That is, the upper limit comparator 20 and the lower limit comparator 2
1, the upper limit comparator 20 sets an allowable upper limit value of the low-voltage power supply circuit 1 as a set value from the VF DA converter 11, and outputs an abnormality detection signal when the external voltage is equal to or higher than the upper limit value. The lower limit comparator 21 sets an allowable lower limit value of the low-voltage power supply circuit 1 as a set value from the IF DA converter 12, and outputs an abnormality detection signal when the external voltage is lower than the lower limit value. The outputs of the upper limit comparator 20 and the lower limit comparator 21 are wired-OR connected and applied to the switches 18 and 19. According to this, not only when a positive high voltage exceeding the allowable value is applied to the low-voltage power supply circuit 1 but also when a negative low voltage exceeding the allowable value is applied, the low-voltage power supply circuit 1 It can be effectively prevented from being destroyed.

In the above-described embodiment, the switches 18 and 19 are connected in series to the remote sensing line 16 and the remote forcing line 17, and both lines 16 and 17 are disconnected by opening these switches. 18 and 19 are connected in parallel to both lines 16 and 17,
Both lines 16 and 17 may be cut off by closing them.

[0028]

According to the present invention, the external voltage is applied to the abnormal voltage detecting circuit in preference to the internal circuit constituting the power supply circuit, and when the external voltage is larger than the allowable voltage, the abnormal voltage is detected. The switch is activated by the detection signal of the voltage detection circuit to prevent the abnormal voltage from being applied to the internal circuit of the power supply circuit. Therefore, even if a short circuit occurs between the terminals of the IC under test, the power supply circuit is effectively protected from the abnormal voltage. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a low-voltage power supply circuit for a DC test of an IC test apparatus according to an embodiment.

FIG. 2 is a configuration diagram of a low-voltage power supply circuit for DC test of another IC test apparatus according to an embodiment.

FIG. 3 is a configuration diagram of a power supply circuit for a DC test of a conventional IC test apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low-voltage power supply circuit 11 DA converter for VF 12 DA converter for IF 20 Comparator 30 Output terminal 31 Abnormal voltage detection circuit 32, 33 Delay circuit 35 Surge absorption circuit 36 Voltage divider circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 31/26-31/3193 G01R 19/165 H02H 3/08-3/253 H02H 7/00-7 / 20

Claims (3)

(57) [Claims] 1. A plurality of power supply circuits each having a constant current source and a constant voltage source for supplying a desired current or voltage to each terminal of an IC under test by an analog signal supplied from a DA converter, and an output terminal of one power supply circuit. From other power supply circuit to IC under test
An abnormal voltage detection circuit having a comparator that compares an external voltage reversely applied through a terminal of the power supply circuit with an allowable voltage of one power supply circuit and outputs an abnormality detection signal when an absolute value of the external voltage is equal to or higher than the allowable voltage. And a delay circuit for delaying the time when the external voltage is applied to the internal circuit of the one power supply circuit so that the external voltage is applied to the abnormal voltage detection circuit preferentially over the internal circuit forming the one power supply circuit An IC test apparatus comprising: a high-voltage / high-speed switch that operates in response to an abnormality detection signal output from an abnormal voltage detection circuit to interrupt application of an abnormal voltage to an internal circuit included in one power supply circuit. 2. The IC according to claim 1, wherein said abnormal voltage detecting circuit is provided with a voltage dividing circuit for dividing an external voltage and applying a divided voltage, and a surge absorbing circuit for absorbing a surge voltage.
Testing equipment. 3. An upper limit comparator for setting an upper limit value as a set value and outputting an abnormal detection signal when the external voltage is equal to or higher than the upper limit value; 3. The IC test apparatus according to claim 1, further comprising a lower limit comparator that outputs an abnormality detection signal when the value is equal to or less than a value, wherein the outputs of the upper limit comparator and the lower limit comparator are wired-OR connected.