Design and Research of Oscillator Circuit with Soft Starting in Power Management Chip

Abstract

Abstract In this paper, an oscillator circuit with a soft start function is designed for DC-DC converters, and its working principle is analyzed. Based on the NUVOTON 0.35 μm BCD technology, the circuit is fully simulated and optimized via Cadence software. Under the typical environment of 5 V and 27°C, the typical oscillation frequency of the oscillator is 800 kHz and the duty ratio is 20%. The expected index is reached and the circuit function is realized. At the same time, a temperature-independent current bias is designed to charge and discharge a capacitor in the oscillator so that the frequency of the oscillator is very little affected by temperature. Under the simulation condition of -40°C–140°C, the operation of the oscillator is stable and its frequency variation is 2.95% over the above temperature range.