Catalyst Semiconductor, Inc.

Horia Profeta

Radu H Iacob

Cornel D Stanescu

Adrian Macarie Tache

Adam Peter Cosmin

A digital potentiometer is disclosed that includes first, second, and third signal terminals. A chain of series-connected impedance elements with multiple tap points is connected between the first and second signal terminals. A plurality of first switching devices are each connected to a respective one of the multiple tap points and to an internal wiper node. A configurable output stage is connected between the internal wiper node and the third signal terminal. The configurable output stage includes a buffer and a second switching device. The second switching device is operable to bypass the buffer. A switching circuit controls switching of the first switching devices. The switching circuit includes a Gray-code counter, a Gray-code decoder, and a make-before-break circuit that controls the timing of the switching of the wiper switches.

Digital potentiometer including output buffer

A digital potentiometer, configurable and programmable using nonvolatile memory is disclosed. A unity-gain configured, rail-to-rail operational amplifier, used as voltage follower of buffer, can be inserted, by programming, between an internal wiper terminal and an output terminal of the digital potentiometer. This way, in certain applications, it is possible to take advantage of the low output resistance given by an analog buffer. The operational amplifier can be shutdown and bypassed by a switching device to provide a circuit behavior similar to a digital potentiometer without an output buffer. Using a dual-writing circuitry, first the complemented data, then the data itself, are written in the nonvolatile memory, improving the reliability. A Gray-code counter having a single bit changed at one time and no decode glitch is present. A make-before-break circuitry gives a short overlap conduction time for any adjacent pair of switches; one being turned-off while the other is turned-on. The resistor array is of high resistivity poly-type, with increased width and number of contacts, providing additional protection in short-circuited operation when the buffer is removed. The switches connected close to resistor array terminals are designed using ESD-proof rules.

Growing community of inventors

Bucharest, Romania

Horia Profeta