The present disclosure provides a low-jitter frequency division clock circuit, including: a clock control signal generation circuit, to generate clock signals having different phases; a low-level narrow pulse width clock control signal generation circuit, to generate a low-level narrow pulse width clock control signal; a high-level narrow pulse width clock control signal generation circuit, to generate a high-level narrow pulse width clock control signal; and a frequency division clock generation circuit, to generate a frequency division clock signal according to low-level narrow pulse width clock control signal and high-level narrow pulse width clock control signal. The delay from a clock input end to an output end of low-jitter frequency division clock circuit is up to three logic gates. Compared with traditional divide-by-2 frequency division clock circuits based on D-flip-flop, the low-jitter frequency division clock circuit of the present disclosure has fewer logic gates, a shorter delay, and lower jitter.

The present disclosure provides a low-jitter frequency division clock circuit, including: a clock control signal generation circuit, to generate clock signals having different phases; a low-level narrow pulse width clock control signal generation circuit, to generate a low-level narrow pulse width clock control signal; a high-level narrow pulse width clock control signal generation circuit, to generate a high-level narrow pulse width clock control signal; and a frequency division clock generation circuit, to generate a frequency division clock signal according to low-level narrow pulse width clock control signal and high-level narrow pulse width clock control signal. The delay from a clock input end to an output end of low-jitter frequency division clock circuit is up to three logic gates. Compared with traditional divide-by-2 frequency division clock circuits based on D-flip-flop, the low-jitter frequency division clock circuit of the present disclosure has fewer logic gates, a shorter delay, and lower jitter.

A CMOS divide by two circuit device comprising a two phase signal input, a first track and hold circuit, a second track and hold circuit, where the signal path from input to output of each track and hold circuit comprises a single switch and a single inverter. In hold mode the circuit device provides cross-coupled inverters with only two stable states, obviating the need for any dedicated start-up, initialization, or phase-forcing circuitry. In addition to its regular two-phase output, it can optionally provide a quadrature two-phase output, both having an output signal frequency equal to one half said input signal frequency.

The present disclosure relates to a method for quadrature error correction using a frequency divider circuit. The method comprises delaying input of data to master input terminals and/or slave input terminals of the frequency divider circuit for correcting a quadrature error between the in-phase and quadrature-phase output signals.

The present disclosure relates to a method for quadrature error correction using a frequency divider circuit. The method comprises delaying input of data to master input terminals and/or slave input terminals of the frequency divider circuit for correcting a quadrature error between the in-phase and quadrature-phase output signals.

Aspects of the disclosure provide methods and apparatuses for generating an internal reset signal that is synchronous to a clock signal. In some embodiments, an apparatus includes a clock switch circuit and a plurality of serially coupled D flip-flops (DFFs). The clock switch circuit receiving the clock signal can output the clock signal in an on state and block the clock signal in an off state. The plurality of serially coupled DFFs are coupled to the clock switch circuit and driven by the clock signal. If an external reset signal is enabled, the plurality of serially coupled DFFs can enable the internal reset signal. If the external reset signal is disabled, after a predefined number of clock signal cycles, the plurality of serially coupled DFFs can disable the internal reset signal.

A quadrature clock skew calibration circuit includes an I-Q clock generator having an input coupled to receive a first clock signal. The I-Q clock generator generates an in phase (I) clock signal and a quadrature (Q) clock signal. The quadrature clock skew calibration circuit includes an I-Q skew sensor having a first input coupled to receive the I clock signal and having a second input coupled to receive the Q clock signal. The I-Q skew sensor generates an I-Q skew signal responsive to a skew between the I and Q clock signals. The quadrature clock skew calibration circuit includes a control circuit having a first input coupled to receive the I-Q skew signal and having a second input coupled to receive a second clock signal. The control circuit varies the duty cycle of the first clock signal responsive to the I-Q skew signal and the second clock signal.

An integrating Analog-to-digital converter has a global counter that outputs a counter code signal including a multiphase signal. It also has a column circuit including: a ramp wave generation circuit outputting a ramp wave voltage; a comparator comparing the ramp wave voltage with a pixel voltage; and a latch circuit latching the counter code signal at output inversion timing of the comparator. An output value of the latch circuit is used as a digital conversion output value per the column circuit. The counter has a phase division circuit outputting, as an LSB of the digital conversion output value of the integrating analog-to-digital converter, a phase division signal to the latch circuit, the phase division signal dividing a phase of the counter code signal. The phase division circuit is arranged to a plurality of column circuits, and the LSB is shared by a plurality of phase division circuits.

An integrating Analog-to-digital converter has a global counter that outputs a counter code signal including a multiphase signal. It also has a column circuit including: a ramp wave generation circuit outputting a ramp wave voltage; a comparator comparing the ramp wave voltage with a pixel voltage; and a latch circuit latching the counter code signal at output inversion timing of the comparator. An output value of the latch circuit is used as a digital conversion output value per the column circuit. The counter has a phase division circuit outputting, as an LSB of the digital conversion output value of the integrating analog-to-digital converter, a phase division signal to the latch circuit, the phase division signal dividing a phase of the counter code signal. The phase division circuit is arranged to a plurality of column circuits, and the LSB is shared by a plurality of phase division circuits.

A frequency divider circuit comprises a first divider chain including at least one first divider cell and a second divider chain coupled to the first divider chain to form an extendable divider chain. The second divider chain includes at least one second divider cell with a respective reset control. An effective length of the extendable divider chain may be altered, dynamically, via the respective reset control. Altering the effective length, dynamically, enables a division ratio of the frequency divider circuit to be changed, dynamically. The frequency divider circuit may be advantageously employed by applications that rely upon a dynamic division ratio, such as a fractional-N (frac-N) phase-locked loop (PLL).