The design and implementation of a novel ADC architecture called ring-ADC for digital voltage regulator module controllers are presented. Based on the principle of voltage-controlled oscillators＇ transform from voltage to frequency,the A/D conversion of ring-ADC achieves good linearity and precise calibration against process variations compared with the delay-line ADC. A differential pulse counting discriminator also helps decrease the power consumption of the ring-ADC. It is fabricated with a Chartered 0.35μm CMOS process, and the measurement results of the integral and differential nonlinearity performance are 0.92LSB and 1.2LSB respectively. The maximum gain error measured in ten sample chips is ± 3.85%. With sampling rate of 500kHz and when the voltage regulator module （VRM） works in steady state, the ring-ADC＇s average power consumption is 2.56mW. The ring-ADC is verified to meet the requirements for digital VRM controller application.
A new approach for the design and implementation of a programmable voltage reference based on an improved current mode bandgap voltage reference is presented. The circuit is simulated and fabricated with Chartered 0. 35μm mixed-signal technology. Measurements demonstrate that the temperature coefficient is ± 36. 3ppm/℃ from 0 to 100℃ when the VID inputs are 11110.As the supply voltage is varied from 2.7 to 5V, the voltage reference varies by about 5mV. The maximum glitch of the transient response is about 20mV at 125kHz. Depending on the state of the five VID inputs,an output voltage between 1.1 and 1.85V is programmed in increments of 25mV.
A novel MOS-only voltage reference is presented,which is based on the threshold voltage difference between p-type and n-type MOSFETs. Its precision is improved by the cancellation of the process variation. The reference has been successfully implemented in a Chartered 0.35μm CMOS process. The occupied chip area is 0. 022mm^2. Measurements indicate that without trimming, the average output voltage error is 6mV at room temperature compared with the simulation result. The temperature coefficient is 180ppm/℃ in the worst case in the temperature range of 0 to 100℃ ,and the line regulation is ± 1.1%. The reference is applied in an adaptive power MOSFET driver.
