Power Chip Cmos Band Gap Reference Source With Fine-tuning The Design And Implementation

CMOS has been the dominant technology for VLSI digital and mixed-signal designs. It is also becoming wide applied in analog IC designs. Voltage reference is one of the most important cells in analog circuit. The paper aims at designing a bandgap reference suited for DC-DC converter using standard CMOS process. This paper presents a general introduction on bandgap reference studies of domestic and aboard, analyzes the theory of bandgap reference, and includes all kinds of trimming method for adjust resistors. Low power, low voltage and high PSRR are the main challenges in designing bandgap reference for switching regulator. A structure fitting for the requiring in switching regulator is selected after study in several bandgap circuit structures. A CMOS bandgap reference is designed to use in DC-DC. This paper contributes mainly in the following: 1.To solve the problem of PSRR, both NMOS input Operation Amplifier and PMOS input Operation Amplifier using in bandgap references are investigated, and the former is selected to use in bandgap reference. An RC filter is introduced to improve the performance of bandgap reference when working in high frequency. 2. Sets up the model of feedback trimming to correct the offset error in bandgap reference, and a very simple and practical trimming method is introduced. Adopted in power chips, the trimming method makes output voltage easy adjusted step by step, with both wide voltage range and high precision, and saves chip area and testing time in manufacture. The test results show that the designed bandgap reference can work in –40-125℃, 3.5uA current, temperature coefficient is 36ppm/℃, under 1.6V to 5V power supply. The output ripples is 5mV when working in switching converter, and the PSRR is 35.6db in the worst case. The voltage reference suggested in this paper applied to DC-DC products.