Pcmo resistor trimmer

Abstract

Using programmable resistance material for a matching resistor, a resistor trimming circuit is designed to reversibly trim a matching resistor to match a reference resistor. The programmable resistance materials such as metal-amorphous silicon metal materials, phase change materials or perovskite materials are typically used in resistive memory devices and have the ability to change the resistance reversibly and repeatably with applied electrical pulses. The present invention reversible resistor trimming circuit comprises a resistance bridge network of a matching resistor and a reference resistor to provide inputs to a comparator circuit for generating a comparing signal indicative of the resistance difference. This comparing signal can be used to control a feedback circuit to provide appropriate electrical pulses to the matching resistor to modify the resistance of the matching resistor to match that of the reference resistor.

Description

FIELD OF THE INVENTION [0001] This invention relates in general to a circuit for resistor trimming, and more particularly, to a circuit for reversible precision adjustment or matching of thin film programmable resistors. BACKGROUND OF THE INVENTION [0002] Resistors play an important role in microelectronic circuits. A resistor is an electrical component designed to have an electrical resistance independent of the applied current or voltage. Two important issues in the fabrication of resistors in microelectronic processing are the accuracy of the individual resistor and the accuracy of the ratio of a pair of resistors. [0003] Many microeletronic circuits, such as precision analog amplifiers, require the individual resistors to have a specific value to achieve the desired circuit performance level. Other circuits, such as differential amplifiers and analog-to-digital (ADC) or digital-to-analog (DAC) converter applications, require the accurate matching of two resistors, but do not req...

AI Technical Summary

Benefits of technology

[0010] In the first embodiment, the present invention reversible resistor trimming circuit comprises a resistor bridge network comprising a matching resistor and a reference resistor, a comparator and a pulse feedback circuit. The reversible resistor trimming circuit first compares the matching resistor to the reference resistor through the comparator circuit. Then the comparator circuit generates a comparing signal indicative of the difference. This signal then controls the polarity, the amplitude or the duration of an electrical pulse provided by the pulse feedback circuit to adjust the resistance of the matching resistor. The process is repeated until the resistances of the matching resistor and the reference resistor are matched. By using a matching resistor made of programmable resistance materials, the present invention provides resistor trimming in both directions, thus allowing the adjustment of resistance over-trimming.

[0012] Depending on the programmable resistance materials used, the feedback circuit of the reversible resistor trimming circuit can provide the resistance adjustment pulses having the polarity, amplitude or duration directly related to the comparing signal. The pulse amplitude, the pulse duration and the number of pulses can also be controlled to improve the resistance overshoot.

[0013] In another embodiment of the present invention, the reversible resistor trimming circuit further comprises a transmission gate between a resistor bridge network and a comparator circuit to isolate the resistor bridge network, and a delay circuit to improve the timing of a feedback circuit.

Problems solved by technology

Two important issues in the fabrication of resistors in microelectronic processing are the accuracy of the individual resistor and the accuracy of the ratio of a pair of resistors.

But for some circuits, this degree of precision is still not adequate.

For example, a resistance variation of merely 0.025 percent may compromise the linearity and accuracy of a 12-bit analog-to-digital converter.

In these prior art resistor trimming methods, the trimming action can be extremely difficult to reverse.

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