An Integrated Ramp Generator for PWM Voltage Regulators

An integrated ramp generator is presented in this paper. For traditional implementations, the amplitude clamp is realized with zener diode to limit the output voltage to ±VZ, while the zener diode is not available for standard CMOS process. The transmission gate is utilized to make the output voltage in the determined range. The reference voltage is provided by a bandgap voltage reference with temperature compensation, which guarantees the temperature stabilization of the frequency of the ramp generator. The ramp generator was fabricated in a commercial CMOS process. The frequency of 44kHz is achieved under the power supply of 3.5V, and the frequency variation of 41kH to 46kHz with the power supply of 3.3V to 5V.