Relayless voltage measurement in automatic test equipment

Details Relayless voltage measurement in automatic test equipment Relayless voltage measurement in automatic test equipment

1998-06-24

2001-02-27

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S073100, C324S1540PB

Reexamination Certificate

active

06194910

ABSTRACT:

This invention relates generally to automatic test equipment, and more specifically to automatic test equipment capable of performing voltage measurements on electronic circuitry.
Automatic test equipment (also known as a “tester”) is commonly used to test semiconductor devices and printed circuit board assemblies to determine whether the devices and assemblies contain defects. In a typical test configuration, testers are programmed to apply test signals to an electronic unit under test (UUT), detect output signals produced by the UUT in response to the test signals, and then compare the detected signals with expected values. Testers are also typically programmed to measure various levels produced by the UUT or other parameters related to the UUT and then compare these measured values with other expected values.
FIG. 1
shows a partial block diagram of a conventional tester
100
used to test a UUT
108
. The tester
100
includes computerized control circuitry
104
coupled to a workstation
102
, which is typically used to develop test programs and enter commands for controlling the tester
100
. Further, the test programs are typically loaded into a memory (not shown) included in the control circuitry
104
, thereby programming the control circuitry
104
to perform various test and analysis operations. For example, the control circuitry
104
may be programmed to control a plurality of source/measurement channels such as a source/measurement channel
106
, which generates and measures signals and/or levels during testing of the UUT
108
.
In particular, the control circuitry
104
may be programmed to control the channel
106
for performing voltage measurements on the UUT
108
. Such voltage measurements frequently cover a range of analog voltage levels. Accordingly, the channel
106
typically includes circuitry (not shown) for measuring a plurality of voltage ranges.
For example, a portion of the voltage measurement circuitry in the channel
106
may be optimized for measuring a low range of voltage levels, while another portion may be optimized for measuring a high range of voltage levels. In some applications, the low voltage range corresponds to levels that fall within the supply rails of the measurement circuitry, and the high voltage range corresponds to levels that might exceed the supply rails of the measurement circuitry.
Further, the voltage measurement circuitry in the channel
106
typically includes some form of switching circuitry to select between the plurality of voltage ranges. Discrete relays are often used to perform this switching function.
Although the tester
100
has been successfully used to perform voltage measurements on semiconductor devices and printed circuit board assemblies, we have recognized some drawbacks. For example, in a typical tester configuration, the front-end of the circuitry for measuring low voltage ranges includes an active buffer, which provides a high impedance interface between the measurement circuitry and the unit under test. This generally ensures good DC performance in the low voltage range.
In contrast, the front-end of the circuitry for measuring high voltage ranges typically includes voltage divider circuitry. This is because levels in the high voltage range might exceed the supply rails of the measurement circuitry and therefore must be reduced by proportional amounts to ensure accurate voltage measurements. However, the voltage divider circuitry generally provides a low impedance interface between the measurement circuitry and the unit under test, thereby compromising DC performance in the high voltage range.
In addition, the discrete relays used for selecting between the voltage ranges are known to be relatively unreliable and costly. Such relays are also known to introduce insertion loss errors that can lead to signal degradation.
Further, discrete relays are generally incompatible with integrated circuit design techniques. Such design techniques are particularly important for testers because in order to test high performance devices and boards, it is frequently necessary to place source and measurement channel circuitry as close as possible to the unit under test. This generally reduces timing errors that can result from impedance mismatches between the unit under test and the signal path to the channel circuitry. The miniaturization that can be achieved using integrated circuit design techniques makes it possible to place more channel circuitry closer to the unit under test. However, channel circuitry that includes discrete relays cannot take full advantage of this miniaturization.
In an alternative tester configuration, the voltage measurement circuitry may include an active buffer with supply inputs that are “boot-strapped” to the input voltage. This ensures that the input voltage level never exceeds the supply rails of the measurement circuitry, thereby reducing the need for selecting between voltage ranges. Consequently, the use of unreliable and costly relays can be avoided. Further, this approach provides a relatively high impedance interface between the measurement circuitry and the unit under test.
However, performing voltage measurement using this alternative configuration also has drawbacks. In particular, because this approach includes buffer circuitry with supply inputs that follow the input voltage, it tends to require excessive amounts of power when performing high voltage measurements. Further, high voltage levels are typically applied to the inputs of the buffer circuitry during the high voltage measurements. These considerations generally make the “boot-strapped” configuration incompatible with integrated circuit design techniques. In addition, because this approach generally does not require separate circuitry for measuring different voltage ranges, performance is usually not optimized for low and high voltage measurements.
It would therefore be desirable to have a tester that can successfully measure a wide range of voltage levels. Such a tester would have voltage measurement circuitry that is highly reliable, low cost, and compatible with integrated circuit design techniques.
SUMMARY OF THE INVENTION
With the foregoing background in mind, it is an object of the invention to provide a tester that can perform voltage measurements on electronic circuitry.
Another object of the invention is to provide a tester that can perform a wide range of voltage measurements while satisfying the loading requirements of the electronic circuitry.
Still another object of the invention is to provide a tester with voltage measurement circuitry that can be implemented using integrated circuit design techniques.
The foregoing and other objects are achieved in a tester having measurement circuitry that includes a plurality of gain stages and a plurality of diodes for selecting among the gain stages.
In a preferred embodiment, the plurality of diodes is used to select among a plurality of current-to-voltage converters. Further, the plurality of current-to-voltage converters is connected to respective bias voltages, which are used to specify voltage ranges measured by the current-to-voltage converters.
In another embodiment, the measurement circuitry includes summing circuitry coupled to the gain stages for providing a level that is proportional to an input voltage level.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.


REFERENCES:
patent: 4092701 (1978-05-01), Bumgardner
patent: 4523143 (1985-06-01), Dvorak
patent: 4524331 (1985-06-01), Faith
patent: 4629910 (1986-12-01), Early et al.
patent: 4646299 (1987-02-01), Schinabeck et al.
patent: 5036218 (1991-07-01), Jaquette
patent: 5045803 (1991-09-01), Perroud et al.
patent: 5070297 (1991-12-01), Kwon et al.
patent: 5083095 (1992-01-01), Madaffari
patent: 5103169 (1992-04-01), Heaton et al.
patent: 5113146 (1992-05-01), de Jager et al.
patent: 5153510 (1992-10-01), Kominsky
patent: 5245222 (1993-09-01), Carobolante
patent: 5313114 (1994-05-01), Poletto et al.
patent: 5363058 (1994-11-01), Sasaki

Affiliated with

Also associated with

Rating

Relayless voltage measurement in automatic test equipment does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Relayless voltage measurement in automatic test equipment, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Relayless voltage measurement in automatic test equipment will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2602255