Temperature and Power Supply Compensated CMOS Clock Circuit Based on Ring Oscillator

Abstract

Improved performance operational amplifier demand has continuously increased. IC designers use the charge pump technique as an advanced solution to implement the amplifier’s rail−to−rail input stage, but the need for a large load capacitor is a serious downside. To reduce this passive component value, high−frequency clock circuits with a 50% duty cycle should be implemented. This paper focuses on designing such a circuit that is further compensated with temperature and power supply, maintaining these performances even when process variations occur, starting from a ring oscillator as the architecture core. A pre−layout 50 MHz center frequency at 25 °C with a 1.6 temperature percentage error was achieved. Post−layout simulations to account for parasitic effects were also performed, with a 48.9 MHz center frequency reached. Distinct methods that control the frequency variation were discussed and established. Performance comparison of the designed PLL with previously reported clock circuits in the CMOS process was concluded, with superior results such as power consumption, die area, and temperature range accomplished.

A Linear Multi-Band Voltage-Controlled Oscillator with Process Compensation for SerDes Applications

“…In most cases, this is difficult to achieve with simple circuit configurations. While usually the voltage variations can be easily managed by supplying the oscillators with voltage regulators [4], the temperature and process variations require more complicated designs or additional control setups and calibrations [5,6]. Thus, regarding the temperature influence on the VCO operation, the performance of current steering oscillators could be compensated by using temperature-dependent current sources, e.g., proportional to absolute temperature (PTAT) or complementary to absolute temperature (CTAT), for temperature variation [6].…”

“…While usually the voltage variations can be easily managed by supplying the oscillators with voltage regulators [4], the temperature and process variations require more complicated designs or additional control setups and calibrations [5,6]. Thus, regarding the temperature influence on the VCO operation, the performance of current steering oscillators could be compensated by using temperature-dependent current sources, e.g., proportional to absolute temperature (PTAT) or complementary to absolute temperature (CTAT), for temperature variation [6]. For process variation detection, more complicated methods must be employed, as the process corner is more difficult to detect automatically and, at the same time, produces a stronger influence on the oscillator performance.…”