A 2.5 V - 5.5 V, 800 kHz Relaxation Oscillator with Delay Cancellation Using Frequency to Voltage Feedback

A 800 kHz relaxation oscillator based on frequency-voltage feedback is designed in a 90 nm BCD technology for the power management unit. The proposed relaxation oscillator adopts frequency-voltage feedback circuit, in which the output frequency is converted to the voltage as a feedback signal to adjust output frequency. By utilizing frequency-voltage feedback, it compensates the delays introduced by the comparators and the capacitor reset logic. The proposed oscillator has minimized sensitivity to supply voltage variations by utilization of a widlar current source. And temperature stability is achieved by the temperature compensation resistance. The proposed oscillator demonstrates a frequency variation of only ±0.7% over the supply voltage range of 2.5 V to 5.5 V, while a variation of ±0.4% over −40 °C - 120 °C.