Relayless voltage measurement in automatic test equipment

• US 6,194,910 B1
• Filed: 06/24/1998
• Issued: 02/27/2001
• Est. Priority Date: 06/24/1998
• Status: Expired due to Term

• Current Assignee: Teradyne Incorporated
• Original Assignee: Teradyne Incorporated
• Inventors: Davis, Richard P., Chen, Jiann-Neng
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): SUNDARAM, T R
• Application Number:
  US09/104,099
• Time in Patent Office: 979 Days
• Field of Search: 324/765, 324/763, 324/764, 324/754, 324/158.1, 324/73.1, 371/20
• US Class Current: 324/762.01
• CPC Class Codes: G01R 31/2834 Automated test systems [ATE]; using microprocessors or computers G01R31/317 takes precedence; ATE for detection of defective computer hardware G06F11/2736
• CPC Class Codes: G01R 31/2844 using test interfaces, e.g. adapters, test boxes, switches, PIN drivers G01R31/2889 takes precedence

Abstract

A tester that is capable of performing voltage measurements on electronic circuits is disclosed. The tester includes voltage measurement circuitry with an input, a plurality of gain stages, and switching circuitry coupled between the input and the gain stages. The switching circuitry includes a plurality of diodes, and a portion of the gain stages includes current-to-voltage converters. Each diode is coupled to a respective current-to-voltage converter. By applying different bias voltages to the respective current-to-voltage converters, the diodes can be made to conduct current for different ranges of voltages at the input. The output of each current-to-voltage converter is proportional to a respective voltage range.

Claims

1. A tester including scaling circuitry for performing voltage measurements on a unit under test, the scaling circuitry comprising:

a measurement input coupled to the unit under test and receiving an input signal to be measured;

a plurality of gain stages having respective inputs coupled to the measurement input and respective outputs generating respective output signals; and

a summing circuit having a plurality of inputs coupled to the respective outputs of the plurality of gain stages and generating an output signal that varies in relation with a sum of the output signals of the plurality of gain stages,

wherein at least one of the gain stages is coupled to the input via a diode, said at least one of the gain stages generating a substantially constant output responsive to a reverse-biased condition of the respective diode, and a variable output responsive to a forward-biased condition of the respective diode, said variable output varying in relation with the input signal to be measured.

2. The tester as recited in claim 1,

wherein one of the plurality of gain stages is a unity-gain amplifier.

3. The tester as recited in claim 1,

wherein the at least one of the gain stages includes at least one current-to-voltage converter.

4. The tester as recited in claim 3,

wherein the at least one current-to-voltage converter includes an operational amplifier with FET inputs.

5. The tester as recited in claim 3,

wherein the at least one current-to-voltage converter receives a bias voltage that defines a transition point between voltage ranges of the voltage measurement circuitry.

6. The tester as recited in claim 1,

further including a plurality of channels connected to the unit under test, the voltage measurement circuitry being incorporated into at least one of the channels.

7. The tester as recited in claim 1, used in a method for manufacturing the unit under test, the method comprising the steps of:

(a) attaching the unit under test to a test fixture;

(b) applying power and test signals to the unit under test;

(c) measuring voltage levels on the unit under test; and

(d) comparing the measured voltage levels with expected values, thereby determining whether the unit under test is defective.

8. A circuit for scaling an input signal for measurement in an automatic test system, comprising:

a measurement input coupled to a unit under test and receiving an input signal to be measured;

a gain circuit having an input coupled to the measurement input and having an output generating an output signal;

at least one gain stage hang an input coupled to the measurement input via an impedance and generating a respective output; and

a summing circuit having a plurality of inputs respectively coupled to the output of the gain circuit and the output of each at least one gain stage,

wherein the output signal of each at least one gain stage varies with the input signal responsive to the measurement input exceeding a respective predetermined threshold in a predetermined direction, and remains substantially constant responsive to the measurement input not exceeding the respective predetermined threshold in the predetermined direction.

9. A circuit as recited in claim 8, wherein the at least one gain stage comprises:

a first switchable gain stage that generates a variable output signal in response to the measurement input exceeding a first predetermined threshold in a positive direction; and

a second switchable gain stage that generates a variable output signal in response to the measurement input exceeding a second predetermined threshold in a negative direction.

10. A circuit as recited in claim 9, wherein the first predetermined threshold is more positive than the second predetermined threshold.

11. A circuit as recited in claim 9, wherein the first and second gain stages each comprise a current-to-voltage converter.

12. A circuit as recited in claim 11, wherein the first and second gain stages each further comprise a diode coupled between the measurement input and the respective current-to-voltage converter.