A capacitor suitable for integration into a monolithic integrated circuit is fabricated in two parallel connected sections. One section, using a thin oxide, constitutes most of the capacitance. A second section fabricated on a thick oxide constitutes a smaller capacitance per unit area but can be laser trimmed to provide a precise capacitance without damage to the integrated circuit. The trimmable section is desirably made using a conductive electrode material that is readily removed with laser energy.

Trim structure for integrated capacitors

A compact and inexpensive variable resistor circuit has a value of resistance that can be set by a data signal. The variable resistor includes a number of variable individual resistances connected in series, and an electronic switch connected in parallel across each individual resistance. The values of the individual resistances are chosen to include a basic resistance value and a compensating resistance value, which corresponds to the impedance of the associated electronic switch in its closed state. The basic value is chosen from the progression 2 0 , 2 1 , 2 2 , 2 3 , and so on, so that the resistance of the variable resistor corresponds to the binary value of data applied to control the electronic switches. Other aspects of the invention include input and control circuitry which is designed to minimize its size and allow it to be packaged on an integrated circuit.

Digitally controlled variable resistor

A trim structure having a nominal resistance value can be adjusted to have a higher or lower value by a combination of fuse blowing and zener zapping. In the preferred embodiment a pair of integrated circuit pads are employed in a trim structure along with a pair of back-to-back zener diodes, a fuse link, and four resistors. In its initial state, with both diodes and the fuse link intact, a particular or nominal resistance value is available. Blowing the fuse link alone produces a second or highest resistance value. Shorting, or zapping, one zener diode produces a third higher than nominal but lower than highest resistance value. Shorting, or zapping, the other zener diode produces a fourth, lower than nominal, resistance value. Shorting, or zapping, both zener diodes produces a fifth lowest resistance value. Thus, five different resistance values are available using only two integrated circuit pads. If desired, the five resistance steps can be made linear by properly selecting the resistor values. In addition, one of the circuit pads can be a common power supply terminal so that only one pad need be added to the integrated circuit chip. Two or more such structures can be fabricated with a common pad by the addition of one additional pad for each such structure.

Multiple trim structure

A semiconductor device includes a resistor network having a plurality of trimming polysilicon resistors. The polysilicon resistors have the same width and different lengths and can be selectively fused according to the value of current which is caused to flow therein. The resultant resistance of the resistor network is changed by selectively fusing the polysilicon resistors. The output characteristic of the semiconductor device can be adjusted by changing the resultant resistance.

Semiconductor device whose output characteristic can be adjusted by functional trimming

Electronic trip units employed within static trip circuit breakers are individually calibrated and automatically adjusted to ensure that the trip transfer characteristics are within specification requirements. A trimming network within the trip unit circuit contains a plurality of parallel resistors each separately connected within the circuit by means of a fusible link. Test input and output values are compared to idealized values that are binary-weighted within a look-up table in the test equipment computer. The percent correction required is determined and the appropriate links are interrupted to provide ideal trip response.

Static trip circuit breaker with automatic circuit trimming

A microminiature terminal-adjustable integrated circuit impedance device comprising a substrate, a plurality of impedance elements formed on the substrate with each impedance element having an impedance, a first input terminal, an output terminal, a plurality of electrically permanently alterable contactless switching elements formed on the substrate, each of the switching elements being associated with one of the plurality of impedance elements and having initially a first switching state and being permanently alterable by application of electrical energy to an opposite switching state, an interconnecting means interconnecting the impedance elements and the switching elements in a first circuit configuration between the first input terminal and the output terminal such that the impedance between the first input terminal and the output terminal is of a first value, and a plurality of adjustment terminals each being connected to a different one of the plurality of switching elements for facilitating the application of electrical energy thereto to cause such switching elements to change to the opposite switching state, whereby the application of electrical energy to selected ones of the adjustment terminals causes a second circuit configuration having a preselected second value to be formed between the first input terminal and the output terminal. Each electrically permanently alterable contactless switching element is comprised of fusible conductive links or shortable diodes, singly or in combination. In the preferred embodiment the device comprises resistive elements fabricated with state-of-the-art thin film or monolithic integrated circuit technology and serves as a variable resistor or as a variable voltage divider performing the function of a fixable contactless trimming potentiometer.

Microminiature integrated circuit impedance device including weighted elements and contactless switching means for fixing the impedance at a preselected value

Marvin B. Rudin

Papers

Microminiature integrated circuit impedance device including weighted elements and contactless switching means for fixing the impedance at a preselected value