IC testing device

Details IC testing device IC testing device

1999-08-31

2001-11-27

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

Reexamination Certificate

active

06323668

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an IC testing apparatus which measures a current flow of a power supply to a semiconductor integrated circuit element constructed by a MOS type circuit to determine whether the element has a defect or not.
BACKGROUND OF THE INVENTION
A MOS type circuit has a feature that it consumes a current only when an active element therein inverts its state, while there flows merely infinitesimal current such as a current flowing through an insulation resistance or so when all of active elements are in their quiescent state.
A testing method has been heretofore known, which comprises the steps of measuring a power supply current flowing through a semiconductor integrated circuit element constructed by a MOS type circuit in its quiescent state, and determining the presence of a short-circuit failure or an open-circuit failure in the semiconductor integrated circuit element depending on whether the measured value of the power supply current is greater than a prescribed value or not, thereby determining whether the semiconductor integrated circuit element has a defect or not.
FIG. 4
shows an example of the conventional testing method. An IC under test
11
has a power supply terminal
11
A connected to a power supply circuit
12
which in turn supplies to the power supply terminal
11
A a power supply voltage Vdd which has been prescribed for the IC under test
11
, and a power supply terminal
11
B of the IC under test
11
through which a current flows out of the IC under test
11
is connected to a common potential point COM.
The power supply circuit
12
comprises an operational amplifier
12
A, and a digital-to-analog (D/A) converter
12
B operating as a voltage source, which is arranged to be capable of supplying a current I
P
(see
FIG. 5
) consumed in a pulse-like manner by the IC under test
11
without any delay.
Specifically, a voltage which is the same as the voltage Vdd to be applied to the power supply terminal
11
A of the IC under test
11
is applied from the D/A converter
12
B to the non-inverting input terminal of the operational amplifier
12
A. An output terminal of the operational amplifier
12
A is connected through a current measurement means
13
to a sensing point SEN, thereby to apply the power supply voltage Vdd to the power supply terminal
11
A of the IC under test
11
through the sensing point SEN as well as to feed a voltage at the sensing point SEN back to the inverting input terminal of the operational amplifier
12
A.
With the above circuit construction of the power supply circuit
12
, by generating the power supply voltage Vdd to the IC under test
11
from the D/A converter
12
B to supply the voltage Vdd to the non-inverting input terminal of the operational amplifier
12
A, the operational amplifier
12
A performs a feedback operation such that the voltage V
1
at the sensing point SEN coincides with the voltage Vdd applied to the non-inverting input terminal of the operational amplifier
12
A, and this feedback operation continues to supply the voltage Vdd to the power supply terminal
11
A of the IC under test
11
.
A current detecting resistor Ri is connected between the output terminal of the operational amplifier
12
A and the sensing point SEN, and a voltage produced across the current detecting resistor Ri is measured, thereby to measure a current Idd passing through the IC under test
11
. In this example, a measurement of the current Idd (see
FIG. 5
) when the IC under test
11
is in its quiescent state will be described. Since the current Idd which flows under the quiescent state is of the order of several micro-amperes (&mgr;A) to several tens of &mgr;A, the resistance of the current detecting resistor Ri will be as high as the order of 100 kilohms (k&ohgr;). Accordingly, two diodes D
1
and D
2
are connected in parallel with the current detecting resistor Ri to bypass the current I
P
that flows when the IC under test
11
is turned to be operative.
A voltage produced by the current Idd flowing through the current detecting resistor Ri is at most of the order of several tens of millivolts (mV). Accordingly, within a range of voltages produced by the current Idd to be measured, the diodes D
1
and D
2
maintain their off state. The voltage produced across the current detecting resistor Ri is taken out by a subtraction circuit
13
A and given to an output terminal
13
B. The voltage V
M
supplied to the output terminal
13
B undergoes an analog-to-digital (A/D) conversion in an A/D converter, for example, and the current Idd is calculated or computed from the value of the voltage V
M
. If the calculated current Idd is greater than a prescribed value, that IC is determined to be defective (failure) or non-conforming article. The measurement of the current Idd is carried out by inputting a test pattern signal to input terminals
11
C of the IC under test
11
and setting the inside of the IC to various quiescent modes, and if the measured values of the current Idd are less than the prescribed value in all of the quiescent modes, the IC is determined to be conforming or pass article.
As noted, this power supply circuit
12
consumes the current I
P
in a pulse-like manner when the IC under test
11
is turned to be operative. Though the current I
P
is supplied from the power supply circuit
12
constituted by the operational amplifier
12
A, a delay or lag is produced in a response of the operational amplifier
12
A because a large current (several mA to several tens of mA) flows transiently through the operational amplifier
12
A. For this reason, a technique or procedure has been adopted, which connects a smoothing capacitor C
1
having a relatively large capacitance to the output side of the power supply circuit
12
, thereby to compensate for a reduction in the voltage/current accompanied by the response lag of the power supply circuit
12
.
As discussed above, the necessity of connecting the smoothing capacitor C
1
having a large capacitance results in that when there occurs any slight noise at the sensing point SEN, a noise current I
c1
flows through the smoothing capacitor C
1
. Since the noise current I
c1
is supplied from the current measurement means
13
, it may interfere with the measurement of the current Idd.
Consequently, the recent trend is toward use of a technique or procedure as shown in
FIG. 6
in which a current detecting resistor Ri is connected between the power supply terminal
11
B of the IC under test
11
through which any current flow is taken out of the IC under test
11
and a point of common potential (COM), and a voltage produced across this current detecting resistor Ri is measured, thereby to calculate or compute the current Idd.
In this case, a short-circuit switch
14
is connected in parallel with the current detecting resistor Ri. This short-circuit switch
14
is controlled to turn on upon an inverting operation of the IC under test
11
, and a large current I
P
occurring at that time is to be bypassed through the short-circuit switch
14
. For this end, a transistor called DMOS or the like is used as the short-circuit switch
14
, the transistor being capable of operating at a high-speed and yet exhibiting a low resistance when it turns on.
With the circuit construction shown in
FIG. 6
, the quiescent current Idd (current flow in quiescent state of the IC under test) hardly changes even if there is some variation in the power supply voltage, provided that the voltage of the power supply circuit
12
remains at a voltage equal to or higher than a fixed value. In other words, there is obtained an advantage that the quiescent current Idd can be measured in a stable condition without being influenced by the noise current passing through the smoothing capacitor C
1
.
On the other hand, however, if a relatively large current should flow through the current detecting resistor Ri due to that the short-circuit switch
14
turning off too early timing or that a short-circuit failure or the like occurs within the IC under test
11
, thereby to produce th

Affiliated with

Also associated with

Rating

IC testing device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with IC testing device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and IC testing device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2600214