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Switching and Autoscaling Circuit for Very Large-Scale Integrated Parametric Circuit Testing

IP.com Disclosure Number: IPCOM000059660D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Zalph, WN: AUTHOR

Abstract

A technique is described whereby a circuit arrangement provides an inexpensive method of autoscaling switched resistors so as to increase measurement sensitivity. The circuit is part of a very large-scale integrated (VLSI) parametric tester and accomplishes autoscaling by switching sense elements instead of switching the gains of the feedback amplifier, as was done in prior art. During input leakage parametric tests, a voltage source forces current through resistor 10, as shown in Fig. 1, into reverse-biased electrostatic discharge (ESD) diode 11. The test will show either that the leakage current is low, measuring in the nanoamps, or that leakage is high, measuring in the micro- or milliampere range. This wide range of leakage, as much as eight orders of magnitude, will cause a severe sensitivity compromise.

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Switching and Autoscaling Circuit for Very Large-Scale Integrated Parametric Circuit Testing

A technique is described whereby a circuit arrangement provides an inexpensive method of autoscaling switched resistors so as to increase measurement sensitivity. The circuit is part of a very large-scale integrated (VLSI) parametric tester and accomplishes autoscaling by switching sense elements instead of switching the gains of the feedback amplifier, as was done in prior art. During input leakage parametric tests, a voltage source forces current through resistor 10, as shown in Fig. 1, into reverse-biased electrostatic discharge (ESD) diode 11. The test will show either that the leakage current is low, measuring in the nanoamps, or that leakage is high, measuring in the micro- or milliampere range. This wide range of leakage, as much as eight orders of magnitude, will cause a severe sensitivity compromise. As a result, an autoscaling circuit, as shown in the autoscaling section of Fig. 2, was devised so as to detect the desired detectable currents. If the output voltage 12 is greater than ten volts, comparator 13 will switch causing positive feedback comparator 14 to latch up at fifteen volts. Scale indicator 15 records the transition. When the transition occurs, field-effect transistor (FET) 16 will switch on, connecting sense resistor 17 in parallel with resistor 10. Autoscale clear circuit 18, to unlatch comparator 14, is provided whenever a new reading occurs. This...