Embodiments of the present disclosure describe methods, apparatuses, and systems for phase-lock loop (PLL) configuration and realization to provide various reference clock frequencies to computing core(s) and processor(s), and other benefits. A post digitally-controlled oscillator (DCO) divider (PDIV) of the PLL may be configured with a dedicated PDIV threshold value corresponding to a dedicated target reference frequency.

An integrated circuit according to an embodiment of the disclosure may include a plurality of function blocks, a spread spectrum clock (SSC) generator that generates a spread spectrum clock based on a frequency modulation rate value, a clock distribution circuit that distributes the generated spread spectrum clock into the plurality of function blocks, a memory that stores predetermined frequency modulation rate values respectively corresponding to the plurality of function blocks, and a control circuit, and the control circuit may be configured to generate the spread spectrum clock based on a smaller frequency modulation rate value among a first frequency modulation rate value and a second frequency modulation rate value respectively corresponding to a first function block and a second function block, which are operating, from among the plurality of function blocks. Moreover, various embodiment found through the present disclosure are possible.

An integrated circuit according to an embodiment of the disclosure may include a plurality of function blocks, a spread spectrum clock (SSC) generator that generates a spread spectrum clock based on a frequency modulation rate value, a clock distribution circuit that distributes the generated spread spectrum clock into the plurality of function blocks, a memory that stores predetermined frequency modulation rate values respectively corresponding to the plurality of function blocks, and a control circuit, and the control circuit may be configured to generate the spread spectrum clock based on a smaller frequency modulation rate value among a first frequency modulation rate value and a second frequency modulation rate value respectively corresponding to a first function block and a second function block, which are operating, from among the plurality of function blocks. Moreover, various embodiment found through the present disclosure are possible.

Embodiments of the present disclosure describe methods, apparatuses, and systems for phase-lock loop (PLL) configuration and realization to provide various reference clock frequencies to computing core(s) and processor(s), and other benefits. A post digitally-controlled oscillator (DCO) divider (PDIV) of the PLL may be configured with a dedicated PDIV threshold value corresponding to a dedicated target reference frequency.

Embodiments of the present disclosure describe methods, apparatuses, and systems for phase-lock loop (PLL) configuration and realization to provide various reference clock frequencies to computing core(s) and processor(s), and other benefits. A post digitally-controlled oscillator (DCO) divider (PDIV) of the PLL may be configured with a dedicated PDIV threshold value corresponding to a dedicated target reference frequency.

The PLL circuit comprises a phase/frequency detector (302), a loop filter (304, 306), a VCO (308) and a feedback loop (320). The VCO can be electrically disconnected from the PLL and comprises a programmable trimming circuit (316) and a current-controlled oscillator (318). For calibration the VCO is electrically disconnected from the loop filter and from the feedback loop, a constant reference voltage is applied to the voltage input (IN), a center frequency programming code (L) is applied to the trimming circuit, the center frequency programming code is iteratively adjusted until a desired center frequency is obtained, a gain programming code (K) is applied to the trimming circuit while the adjusted code is still applied, and the gain programming code is iteratively adjusted until a desired gain is obtained. Then the VCO is connected to the PLL, which is then ready for normal operation.

The PLL circuit comprises a phase/frequency detector (302), a loop filter (304, 306), a VCO (308) and a feedback loop (320). The VCO can be electrically disconnected from the PLL and comprises a programmable trimming circuit (316) and a current-controlled oscillator (318). For calibration the VCO is electrically disconnected from the loop filter and from the feedback loop, a constant reference voltage is applied to the voltage input (IN), a center frequency programming code (L) is applied to the trimming circuit, the center frequency programming code is iteratively adjusted until a desired center frequency is obtained, a gain programming code (K) is applied to the trimming circuit while the adjusted code is still applied, and the gain programming code is iteratively adjusted until a desired gain is obtained. Then the VCO is connected to the PLL, which is then ready for normal operation.

In described examples, a feedback loop has phase detection (PD) circuitry that has a reference input to receive a reference frequency signal, a feedback input to receive a feedback signal, and phase difference outputs. A phase to digital converter (P2DC) includes a first phase to charge converter (PCC) that has a gain polarity and a first phase error output; a second PCC that has an opposite gain polarity and a second phase error output. A differential loop filter has an amplifier with an inverting input coupled to the first phase error output and a non-inverting input coupled to the second phase error output. An analog to digital converter (ADC) has an input coupled to an output of the differential loop filter. A feedback path is coupled to the output of the P2DC, with an output of the feedback path providing the feedback signal to the PD feedback input.

In described examples, a feedback loop has phase detection (PD) circuitry that has a reference input to receive a reference frequency signal, a feedback input to receive a feedback signal, and phase difference outputs. A phase to digital converter (P2DC) includes a first phase to charge converter (PCC) that has a gain polarity and a first phase error output; a second PCC that has an opposite gain polarity and a second phase error output. A differential loop filter has an amplifier with an inverting input coupled to the first phase error output and a non-inverting input coupled to the second phase error output. An analog to digital converter (ADC) has an input coupled to an output of the differential loop filter. A feedback path is coupled to the output of the P2DC, with an output of the feedback path providing the feedback signal to the PD feedback input.

A frequency synthesizer employs a combination of a low divide ratio divider phase-locked loop (PLL) and a wide band, on-chip voltage-controlled oscillator (VCO). To reduce phase noise, low divide ratio phase detection is employed. By using the off-chip PLL with a bank of on-chip VCOs, the frequency synthesizer may have enhanced frequency stability and avoid having to include an acquisition circuit. A separation between the PLL and VCO may reduce integer boundary spurs (IBS) eliminating or reducing a need for a filter bank and switches reducing a complexity of the frequency synthesizer.