Abstract: A apparatus includes a reference signal generator, a droop detection circuit, a digital frequency-locked loop (DFLL), and a DFLL control circuit. The reference signal generator that receives a digital value and produces a pulse-density modulated signal based on the digital value. The droop detection circuit converts the pulse-density modulated signal to an analog signal, compares the analog signal to a monitored supply voltage, and responsive to detecting a droop of the monitored supply voltage below a designated value relative to the analog signal, produces a droop detection signal. The DFLL provides a clock signal for synchronizing circuitry within a domain of the monitored supply voltage. The DFLL control circuit, responsive to receiving the droop detection signal, causes the DFLL to slow the clock signal.

Abstract: A apparatus includes a reference signal generator, a droop detection circuit, a digital frequency-locked loop (DFLL), and a DFLL control circuit. The reference signal generator that receives a digital value and produces a pulse-density modulated signal based on the digital value. The droop detection circuit converts the pulse-density modulated signal to an analog signal, compares the analog signal to a monitored supply voltage, and responsive to detecting a droop of the monitored supply voltage below a designated value relative to the analog signal, produces a droop detection signal. The DFLL provides a clock signal for synchronizing circuitry within a domain of the monitored supply voltage. The DFLL control circuit, responsive to receiving the droop detection signal, causes the DFLL to slow the clock signal.

Abstract: An oscillator circuit includes a first oscillator, a second oscillator, and a calibration circuit to calibrate the first and second oscillators. The first oscillator is supplied with a first supply voltage, and the second oscillator is supplied with a second supply voltage. The calibration includes setting a frequency control of the second oscillator at a target frequency. Then, a voltage control of the second supply voltage is adjusted incrementally until a first control value is identified at which a second oscillator output frequency matches the target frequency. Then, a voltage control of the first supply voltage is set to the first control value. Then, the voltage control for the first supply voltage is adjusted incrementally until a second control value is identified at which a first oscillator output frequency is as close to the second oscillator output frequency as is achievable, but does not exceed it.