News Column

Patent Issued for Runtime Compensated Oscillator

August 5, 2014



By a News Reporter-Staff News Editor at Journal of Technology -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventor Feldtkeller, Martin (Munich, DE), filed on June 9, 2011, was published online on July 22, 2014.

The patent's assignee for patent number 8786375 is Infineon Technologies Austria AG (Villach, AT).

News editors obtained the following quote from the background information supplied by the inventors: "Oscillators are widely used in electronic circuits for generating a clock signal. Those clock signals are, for example, used in switching converters for defining the frequency of a pulsewidth modulated (PWM) signal, in digital circuits for synchronizing the operation of individual devices in the digital circuit, or in communication devices for synchronizing a transmitter and a receiver each coupled to a transmission channel.

"Different types of oscillators are known, such as quartz oscillators, micromechanical oscillators, or relaxation oscillators. Relaxation oscillators include a capacitive component that is periodically charged and discharged with a constant current in order to generate a triangular oscillating signal. In this kind of oscillator, a voltage across the capacitive component is compared with at least one reference voltage in order to define the times when the oscillator switches between charging and discharging, and vice versa, of the capacitive component. This requires the use of at least one comparator. Comparators, however, have a propagation delay that is dependent on a plurality of different factors and that influence the frequency of the oscillating signal. The propagation delay of a comparator can be dependent on variations in its manufacturing process, but also on external factors during its operation, such as the ambient temperature. Those external factors, that may vary over time, may result in an oscillating signal with a time-varying frequency.

"There is a need to provide a relaxation oscillator that generates an oscillating signal with a stable frequency and that can be integrated in an integrated circuit, and to provide a method for generating an oscillating signal with a fixed frequency."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "A first aspect of the invention relates to a method for generating an oscillating signal. The method includes providing a plurality of n, with n.gtoreq.2, capacitive storage elements. Each of these capacitive storage elements can assume a first charging state and a second charging state, providing at least two threshold detectors. Each capacitive storage element has one threshold detector associated thereto. Each threshold detector is connected to detect the charging state of the at least one associated capacitive storage element. One oscillation period of the oscillating signal is generated such that it includes at least n subsequent sub-periods. Generating each sub-period includes changing the charging state of one capacitive storage element from the first charging state as detected by the associated threshold detector to the second charging state as detected by the associated threshold detector. Changing the charging state includes providing a constant charging current to the capacitive storage element. Generating each sub-period further includes setting back the charging state of the one capacitive storage element to the first charging state after the sub-period.

"A second aspect relates to a method for generating an oscillating signal having subsequent oscillator signal periods. The method includes providing n, with n.gtoreq.2, oscillator units, wherein each of the oscillator units is configured to alternately assume an active mode and a preset mode. Each oscillator unit has an internal state that can assume a first and a second state and has an internal runtime and comprises a capacitive storage element. One oscillator signal period of the oscillator signal is generated as a sequence of at least n sub-periods, each sub-period having a sub-period duration defined by one oscillator unit in the active mode, where the duration of two directly subsequent sub-periods are defined by two different oscillator units. Each oscillator unit changes its internal state from the first state to the second state in the active mode, and is preset to the first state in the preset state. The first state and the second state are defined by a charging state of the corresponding capacitive storage element, with the charging state being defined by an amount of electrical charge stored in the capacitive storage element. In the capacitive storage element the first and the second state comprises a same offset charge that is dependent on the internal runtime, so that a charge difference between the amount of charge stored in the capacitive storage element in the first state and the amount of charge stored in the capacitive storage element in the second state is independent on the internal runtime.

"A third aspect relates to a method for generating a time duration of one sub-clock signal of a clock signal. The method includes precharging a capacitive storage element until a threshold detector detects that a voltage at a first terminal of the capacitive storage element has crossed a threshold. Charging the capacitive storage element stops when the threshold detector detects that the voltage at a first terminal of the capacitive storage element has crossed a first threshold. Charging the capacitive storage element continues when a time interval for generating the sub-clock begins. The sub-clock is terminated when the threshold detector detects that the voltage at a first terminal of the capacitive storage element has crossed a second threshold.

"A fourth aspect relates to an oscillator, including n, with n.gtoreq.2, oscillator units. Each of the oscillator units is configured to alternately assume an active mode and a preset mode. Each oscillator unit has an internal state that can assumes a first and a second state and has an internal runtime and comprises a capacitive storage element. The oscillator circuit is configured to generate one oscillator signal period of the oscillator signal as a sequence of at least n sub-periods, each sub-period having a sub-period duration defined by one oscillator unit in the active mode. The duration of two directly subsequent sub-periods are defined by two different oscillator units. Each oscillator unit changes its internal state from the first state to the second state in the active mode, and is preset to the first state in the preset state. The first state and the second state is defined by a charging state of the corresponding capacitive storage element, with the charging state being defined by an amount of electrical charge stored in the capacitive storage element. The capacitive storage elements in the first and in the second state comprise a same offset charge that is dependent on the internal runtime, so that a charge difference between the amount of charge stored in the capacitive storage element in the first state and the amount of charge stored in the capacitive storage element in the second state is independent on the internal runtime.

"A further aspect relates to an oscillator circuit including at least two oscillator units. The at least two oscillator units are configured in an alternating order to generate a frequency determining sub-period, where generating the sub-period comprises charging a capacitive storage element from a first charging state to a second charging state. A runtime error on detection of the second charging state is compensated by precharging the capacitive storage element during a preceding sub-period to the first charging state being dependent on the runtime error."

For additional information on this patent, see: Feldtkeller, Martin. Runtime Compensated Oscillator. U.S. Patent Number 8786375, filed June 9, 2011, and published online on July 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8786375.PN.&OS=PN/8786375RS=PN/8786375

Keywords for this news article include: Infineon Technologies Austria AG.

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Source: Journal of Technology


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