Frequency lock loop (FLL) circuits, low voltage dropout regulator circuits, and related methods are disclosed. An example gate driver integrated circuit includes a first die including a FLL circuit to generate a first clock signal having a first phase and a first frequency, a second clock signal having the first frequency and a second phase different from the first phase, and control a plurality of switching networks to increase the first frequency to a second frequency, and generate a feedback voltage based on the second frequency, and a second die coupled to the first die, the second die including a low dropout (LDO) circuit and a driver, the driver configured to control a transistor based on the first frequency, the second die configured to be coupled to the transistor, the LDO circuit to generate a pass-gate voltage based on an output current of the LDO circuit satisfying a current threshold.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

A high voltage generating circuitry includes a charge-pump and control loop; the control loop includes a voltage divider which receives a high voltage and provides a divided high voltage output. A first circuit element provides a first voltage difference signal. A controller generates a feedback signal based on the first voltage difference signal. An oscillator generates clock signals for operating the charge-pump circuitry, with the frequency of the clock signals being controlled with a control signal. A feedforward path with a second circuit element combines a second reference voltage and a second voltage generated by inverting the supply voltage for obtaining a second voltage difference signal. A third circuit element generates a feedforward compensation signal inversely proportional to a voltage difference between the supply voltage and the second reference voltage. A fourth circuit element generates the control signal by summing the feedback signal and the feedforward compensation signal.

An atomic oscillator includes: an atom cell in which alkali metal atoms are accommodated; a light-emitting element that emits light beams for exciting the alkali metal atoms toward the atom cell; a shield that includes a first member, a second member, and a high thermal resistance portion and accommodates the atom cell, the first member and the second member being members having a magnetic shielding property, and the high thermal resistance portion being provided between the first member and the second member and having a thermal resistance higher than thermal resistances of the first member and the second member; a temperature control element that controls a temperature of the first member; a heater that is thermally coupled to the second member; and a light-receiving element that receives light beams passing through the atom cell.

An atomic oscillator includes: an atom cell in which alkali metal atoms are accommodated; a light-emitting element that emits light beams for exciting the alkali metal atoms toward the atom cell; a shield that includes a first member, a second member, and a high thermal resistance portion and accommodates the atom cell, the first member and the second member being members having a magnetic shielding property, and the high thermal resistance portion being provided between the first member and the second member and having a thermal resistance higher than thermal resistances of the first member and the second member; a temperature control element that controls a temperature of the first member; a heater that is thermally coupled to the second member; and a light-receiving element that receives light beams passing through the atom cell.

Frequency lock loop (FLL) circuits, low voltage dropout regulator circuits, and related methods are disclosed. An example gate driver integrated circuit includes a first die including a FLL circuit to generate a first clock signal having a first phase and a first frequency, a second clock signal having the first frequency and a second phase different from the first phase, and control a plurality of switching networks to increase the first frequency to a second frequency, and generate a feedback voltage based on the second frequency, and a second die coupled to the first die, the second die including a low dropout (LDO) circuit and a driver, the driver configured to control a transistor based on the first frequency, the second die configured to be coupled to the transistor, the LDO circuit to generate a pass-gate voltage based on an output current of the LDO circuit satisfying a current threshold.

A self-start-up control circuit adaptable to an oscillation circuit includes a state circuit that generates a reset signal according to a level of a control voltage for a voltage-controlled oscillator (VCO) of the oscillation circuit; and a start-up circuit that starts up the VCO by generating an enable signal according to the reset signal.

A self-start-up control circuit adaptable to an oscillation circuit includes a state circuit that generates a reset signal according to a level of a control voltage for a voltage-controlled oscillator (VCO) of the oscillation circuit; and a start-up circuit that starts up the VCO by generating an enable signal according to the reset signal.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

A system, circuit and method for providing a controlled oscillator frequency with reduced phase noise for use in a communication system. In one embodiment, the circuit includes a delay line coupled to an output of a voltage controlled oscillator (VCO). The circuit also includes a combiner having a first input coupled to an output of the delay line, and a second input coupled to the output of the VCO. An output of the combiner is coupled to a control input of the VCO.