Abstract:
In described examples, a frequency modulated continuous wave (FMCW) radar includes a reference clock, a phase locked loop (PLL), a pulse generator, a counter, a chirp ramp control circuit, and a synchronization state machine. The reference clock generates a reference clock signal. The PLL generates a feedback clock signal in response to the reference clock signal, and an output signal in response to the feedback clock signal. The pulse generator outputs a chirp start pulse in response to the reference clock signal. The counter increments a count in response to the feedback clock signal. The synchronization state machine provides a chirp ramp signal to a chirp ramp control circuit in response to the reference clock signal, the feedback clock signal, the chirp start pulse, and the count. The chirp ramp control circuit causes the PLL to ramp a frequency of the output signal in response to the chirp ramp signal.
Abstract:
Digital control of a crystal oscillator is implemented in a manner that allows frequency accuracy to be traded off dynamically with power consumption. The oscillator transitions between a less accurate/lower power mode and a high accuracy/higher power mode smoothly without requiring any external clock source during the transition. Power consumption is optimized because the crystal oscillator provides the clock source during transitions between the power modes and no other clock source is needed for these transitions. The system can also optimize the startup time and steady state power consumption independently.
Abstract:
Digital control of a crystal oscillator is implemented in a manner that allows frequency accuracy to be traded off dynamically with power consumption. The oscillator transitions between a less accurate/lower power mode and a high accuracy/higher power mode smoothly without requiring any external clock source during the transition. Power consumption is optimized because the crystal oscillator provides the clock source during transitions between the power modes and no other clock source is needed for these transitions. The system can also optimize the startup time and steady state power consumption independently.
Abstract:
A circuit includes a crystal oscillator to generate an output frequency for a circuit. A driving oscillator generates a startup signal having a driving frequency that is provided to activate the crystal oscillator. The driving frequency of the startup signal is varied over a range of frequencies that encompass the operating frequency of the crystal oscillator to facilitate startup of the crystal oscillator.