Clock gating

About: Clock gating is a research topic. Over the lifetime, 7838 publications have been published within this topic receiving 107903 citations.

System and method for testing a clock circuit

Abstract: A test circuit determines whether a frequency of an output clock signal of a clock circuit is above an output threshold frequency. An input clock signal of the clock circuit is set to an elevated frequency that is higher than a specified frequency. A first counter counts the number of clock cycles of the input clock signal in a test interval to within a tolerance of the elevated frequency. The tolerance of the elevated frequency is higher than a tolerance of the specified frequency. A second counter counts the number of clock cycles of a feedback clock signal in the test interval. A comparator determines whether the frequency of the output clock signal is above the output threshold frequency based on the number of clock cycles of the input clock signal and the number of clock cycles of the feedback clock signal.

Apparatus and method for controlling power gating in an integrated circuit

Abstract: An integrated circuit comprises a block of components to be power gated and power gating circuitry for selectively isolating the components from the source voltage supply to achieve such power gating. A voltage regulator provides a control voltage to the power gating circuitry when performing power gating operations. The control voltage may be set to any of a plurality of predetermined voltage levels. An adaptive controller receives operating parameter data from either or both of the block of components and the power gating circuitry, that operating parameter data being indicative of leakage current. The adaptive controller issues a feedback signal to the voltage regulator whose value depends on the received operating parameter data. The voltage regulator responds to the feedback signal to change the control voltage between the predetermined voltage levels until the operating parameter data indicates that a desired leakage current is obtained within the power gating circuitry.

Programmable multiphase clock divider

Abstract: A programmable multiphase clock divider for selectively frequency dividing a multiphase input clock to provide a lower-frequency, self-aligned, multiphase output clock includes a counter, combinational logic circuitry, a multiphase signal generator and a multiplexor. With the counter serving as the sole frequency divider element, multiple phase-aligned clock phases are generated which are then programmably multiplexed to provide the desired frequency-divided, self-aligned clock phases. The counter, in response to a preset signal and an input clock phase, generates a multibit count signal, one bit of which forms the first output clock phase. The combinational logic circuitry receives a programming signal for decoding the multibit count signal to generate the counter preset signal and an output control signal. The multiphase signal generator successively latches the first output clock phase with the aforementioned input clock phase and additional input clock phases to generate a number of synchronous, intermediate clock phases. The multiplexor, in response to the output control signal, multiplexes the intermediate clock phases to provide further output clock phases. All of the output clock phases are phase-aligned with one another and are at a lower frequency than that of the input clock phase. Multiple ones of such clock dividers can be programmed to frequency divide by selected prime numbers and cascaded to achieve virtually any desired frequency division ratio while maintaining self-aligned output clock phases.

Clock generator and clock generating method capable of varying clock frequency without increasing the number of delay elements

Abstract: A clock generator including a frequency multiplier, a phase lock circuit and a frequency divider. The frequency multiplier generates a frequency multiplied clock by multiplying the frequency of an input clock. The phase lock circuit detects a phase difference between the input clock and a frequency divided clock, and generates, by delaying the frequency multiplied clock by an amount corresponding to the phase difference, a phase-locked clock with its phase locked with the input clock. The frequency divider detects in every fixed cycle a particular pulse of the phase-locked clock, and generates the frequency divided clock by dividing the phase-locked clock with reference to the particular pulse of the phase-locked clock. In particular, the frequency divider detects the particular pulse immediately previous to a falling edge of the input clock. This can reduce the phase difference between the input clock and the phase-locked clock, and hence to solve a problem of a conventional clock generator in that a delay time of a digital delay line in a phase lock circuit must be lengthened with a reduction in the multiplication number of the frequency multiplied clock, which requires a greater number of delay elements because of a large occupying area of the delay elements and a decoder, thereby increasing the circuit scale and cost of a chip to reduce the multiplication number of the frequency multiplied clock.

System having both externally and internally generated clock signals being asserted on the same clock pin in normal and test modes of operation respectively

Abstract: A clock signal driven device has a clock pin for receiving an externally generated clock signal during normal operation. Internal circuitry coupled to the clock pin is responsive to the externally generated clock signal during normal operation. The device also has a clock source, such as a PLL, that provides an internal clock signal, and an internal clock generator that during a test mode of operation generates from the internal clock signal and asserts on the clock pin a test clock signal. The test clock signal has substantially similar signal characteristics to predefined signal characteristics of the externally generated clock signal. The device's internal circuitry is responsive to the test clock signal during the test mode of operation.