A Digital TCXO with New Trimming Method
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Recently, the demand for the stable temperature compensated crystal oscillators (TCXO) is increasing more and more and digital TCXOs (DTCXO) have been studied extensively because of their higher frequency accuracy and onechip implementation possibility. To develop a VLSI TCXO circuit, the DTCXO using capacitor array which is directly controlled by the digital code from the memory was proposed and how to organize the capacitor array has been studied. In this work, a new capacitor array scheme, called TACA (temperature compensated capacitor array) is proposed. It guarantees monotonicity and saves the silicon area at the same time. We also have developed TCXO, which can be used over wide range of frequency. The oscillator and the capacitor array were fabricated with a 0.5μm CMOS process. Complete digital trimming of the DTCXO with 0.2ppm trimming accuracy was achieved.
Abstract
Recently, the demand for the stable temperature compensated crystal oscillators (TCXO) is increasing more and more and digital TCXOs (DTCXO) have been studied extensively because of their higher frequency accuracy and onechip implementation possibility. To develop a VLSI TCXO circuit, the DTCXO using capacitor array which is directly controlled by the digital code from the memory was proposed and how to organize the capacitor array has been studied. In this work, a new capacitor array scheme, called TACA (temperature compensated capacitor array) is proposed. It guarantees monotonicity and saves the silicon area at the same time. We also have developed TCXO, which can be used over wide range of frequency. The oscillator and the capacitor array were fabricated with a 0.5μm CMOS process. Complete digital trimming of the DTCXO with 0.2ppm trimming accuracy was achieved.