A circuit device includes a comparator, a reference voltage generation circuit, and a coupling control circuit. The comparator is configured to output a power-on reset signal by comparing a monitoring target voltage generated from a power supply voltage with a reference voltage. The reference voltage generation circuit is configured to generate the reference voltage. The coupling control circuit is coupled between a power supply voltage node and a reference voltage node. The coupling control circuit couples the reference voltage node and the power supply voltage node in a predetermined period after the power supply voltage is supplied.

An all-digital phase locked loop (ADPLL) is provided. The ADPLL comprises a pattern generator adapted to generate a frequency control word (FCW) based on a predefined setting and a system clock. In addition, the ADPLL comprises a phase accumulator adapted to translate the FCW into a phase trajectory. The ADPLL further comprises a phase comparator adapted to generate a phase error signal representing a difference between the phase trajectory and the phase of an output oscillation frequency. Moreover, the ADPLL comprises a controller adapted to control a phase of the output oscillation frequency with respect to the phase trajectory.

A clock circuit includes a set of level shifters, a duty cycle adjustment circuit and a calibration circuit. The set of level shifters is configured to output a first set of phase clock signals having a first duty cycle. Each level shifter is configured to output a corresponding phase clock signal of the first set of phase clock signals. The duty cycle adjustment circuit is configured to generate a first clock output signal responsive to at least one of a first or second phase clock signal of the first set of phase clock signals or a set of control signals. The first clock output signal has a second duty cycle. The calibration circuit is configured to perform a duty cycle calibration of the second duty cycle based on an input duty cycle, and generate the set of control signals responsive to the duty cycle calibration of the second duty cycle.

In described examples, a method of operating a transceiver with a transmitter and a receiver includes generating a frequency reference. In the transmitter: A phase locked loop (PLL) generates a first voltage controlled oscillator (VCO) control voltage responsive to the frequency reference. A VCO in the transmitter generates a transmitter VCO signal responsive to the first VCO control voltage, and the PLL is locked to the transmitter VCO signal. In the receiver: A signal is received. A receiver VCO generates a receiver VCO signal responsive to the first or a second VCO control voltage. The receiver VCO signal is multiplied by the received signal to generate an I component, and by the received signal phase shifted by 90° to generate a Q component. The second VCO control signal is generated responsive to the I component and the Q component.

An electronic circuit including: a differential multiplier circuit with a first differential input and a second differential input and a differential output; and a phase locked loop (PLL) circuit including: (1) a balanced differential mixer circuit with a first differential input electrically connected to the differential output of the differential multiplier circuit, a second differential input, and an output; (2) a loop filter having an output and an input electrically connected to the output of the balanced differential mixer circuit; and (3) a voltage controlled oscillator (VCO) circuit having an input electrically connected to the output of the loop filter and with an output electrically feeding back to the second differential input of the balanced differential mixer circuit.

A clock circuit includes a set of level shifters, a duty cycle adjustment circuit and a calibration circuit. The set of level shifters is configured to output a first set of phase clock signals having a first duty cycle. The duty cycle adjustment circuit is configured to generate a first clock output signal responsive to a first phase clock signal, a second phase clock signal and a set of control signals, and adjust the second duty cycle responsive to the set of control signals or a phase difference between the first phase clock signal and the second phase clock signal. The calibration circuit is configured to perform a duty cycle calibration of a second duty cycle of the first clock output signal based on an input duty cycle, and to generate the set of control signals responsive to the duty cycle calibration.

Upon external display configuration change, a graphics display driver or any suitable hardware or software modifies the clock frequency of the processor core (e.g., graphics processor core) display engine. The graphics display driver or any suitable hardware or software reprograms the core display clock PLL (CDCLK PLL) to a new frequency, without any dead clocks during such frequency change. A divide-by-2 divider changes the frequency of the PLL on the fly or dynamically. The technique may not require the PLL to be turned off and turned back again at all.

A frequency generator is disclosed. The frequency generator is for generating an oscillator clock according to a reference clock, and the frequency generator is used in a frequency hopping system that switches a carrier frequency among a plurality of channels, and the carrier frequency further carries a modulation frequency for data transmission. The frequency generator includes: a frequency hopping and modulation control unit, arranged for generating a current channel according to a channel hopping sequence and a frequency command word (FCW) based on the reference clock, a digital-controlled oscillator (DCO), arranged for to generating the oscillator clock according to an oscillator tuning word (OTW) obtained according to the estimated DCO normalization value. An associated method is also disclosed.

An all-digital phase locked loop (ADPLL) is provided. The ADPLL comprises a pattern generator adapted to generate a frequency control word (FCW) based on a predefined setting and a system clock. In addition, the ADPLL comprises a phase accumulator adapted to translate the FCW into a phase trajectory. The ADPLL further comprises a phase comparator adapted to generate a phase error signal representing a difference between the phase trajectory and the phase of an output oscillation frequency. Moreover, the ADPLL comprises a controller adapted to control a phase of the output oscillation frequency with respect to the phase trajectory.

Upon external display configuration change, a graphics display driver or any suitable hardware or software modifies the clock frequency of the processor core (e.g., graphics processor core) display engine. The graphics display driver or any suitable hardware or software reprograms the core display clock PLL (CDCLK PLL) to a new frequency, without any dead clocks during such frequency change. A divide-by-2 divider changes the frequency of the PLL on the fly or dynamically. The technique may not require the PLL to be turned off and turned back again at all.