Microbridge MBT-303-A Rejustor

Microbridge Technologies’ MBT-303-A rejustor (re-adjustable resistor) is a passive electronic Temperature Compensation (eTC) divider. The MBT-303-A rejustor is ideal for managing temperature in precise analog circuits, optical systems, sensors, and power supply compensation and calibration across a wide range of military, aerospace, automotive, industrial, medical, and consumer applications.

The MBT-303-A, which employs eTC technology, is a high accuracy dual 30K ohm divider (two resistors in series) where each resistor can be set to any value between 21K and 30K ohms with an accuracy of 0.01%. Having two rejustor elements in the same package makes it easier to implement divider networks where resistors must be equally matched.

Microbridge MBT-303-A RejustorThe MBT-303-A rejustor enables automated, independent adjustment of both resistance and the Temperature Coefficient of Resistance (TCR), which determines how resistance changes as the temperature changes. Control of TCR that is independent of ohmic value enables the MBT-303-A to not only provide one to two orders of magnitude performance improvement for analog designs but also maintain consistency of resistance over an extended temperature range for circuits that require set-on-test calibration and compensation.

Until now it has not been possible to automate the adjustment process to compensate for temperature-induced drift using only analog components. The eTC-based MBT-303-A, configured using Microbridge’s Rejust-it software, is the first passive device to solve analog problems in the analog domain using devices that are suitable for small volume niche markets to mass produced commercial products.

Rejustors shift compensation in temperature-sensitive applications from an active process to a passive one. Traditionally, engineers have had to compensate for changes in temperature using complex digital circuitry compromised of a microprocessor and D/A converters switching out fixed resistances. This approach is limited in accuracy (about .1% for a compensation circuit employing 10 switches) and consumes a notable amount of power. The additional circuitry involved also adds further uncertainties that reduce accuracy.

Rejustors eliminate many of the detrimental side-effects associated with digital compensation to achieve accurate and cost-effective temperature compensation. In-circuit adjustability of both ohmic resistance and TCR, as well as support for positive and negative temperature coefficients, enables developers to apply compensation after devices such as sensors are fully manufactured and hermetically sealed. Rejustors also eliminate the need for thin and thick film laser trimming currently used in IC manufacturing. The MBT-303-A requires no power source during operation, does not suffer from wiper resistance, and no external temperature sensor is required since the rejustor is its own temperature sensor as well as adjustment controller. Rejustors are capable of replacing complex digital potentiometers and can be used to raise the performance of lower cost analog circuits to the level of higher precision circuits.

Available in a 16-lead QFN package or 8-pin SOIC package, the new MBT-303-A passive rejustor is currently sampling and costs $1.67 each in quantities of 1,000.

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