Monotonous debugging method of digital control capacitance switch array of crystal oscillator

Abstract

The invention discloses a monotonous debugging method of a digital control capacitance switch array of a crystal oscillator, a digital decoding circuit converts an input digital control bit into a practical control signal of a switch array, each switch in the switch array correspondingly controls one capacitance unit of a multi-layer metal interdigital capacitor array, the quantity of the capacitance units accessing the crystal oscillator in the multi-layer metal interdigital capacitor array is adjusted through the on-off of each switch in the switch array, i.e.the total capacitance of the crystal oscillator is adjusted, thereby achieving the monotonous debugging of the crystal oscillator. The invention dose not need to use a D / A convertor, and directly controls the multi-layer metal interdigital capacitor switch array through decoding the multi-bit digital control signal of a base band to achieve the monotonous debugging. The debugging method and an oscillator system are suitable for a wireless mobile communication integrated circuit, meet the requirements of small volume, low cost and mass production for products, and can serve as high precise reference basis of a phase locked loop circuit of the terminal of the commercial wireless mobile communication integrated circuit.

Description

technical field [0001] The invention relates to a digitally controlled capacitive switch array monotone tuning method, in particular to a digitally controlled capacitive switch array monotone tuning method for a high-precision crystal oscillator used in a wireless mobile communication integrated circuit. Background technique [0002] In the application of wireless mobile communication terminals, a stable frequency reference source is an important part of the phase-locked loop circuit. The GSM and WCDMA standards require the accuracy of the carrier frequency to be below 0.1ppm, and the TD-LTE standard puts forward higher requirements for the accuracy of the carrier frequency. As an automatic frequency control (AFC) tuning circuit for synchronizing base station and terminal frequency accuracy, this requirement must be met. [0003] Usually, the AFC calibration of the terminal is converted from the baseband multi-bit digital control signal through the D / A converter into an ana...

AI Technical Summary

Problems solved by technology

For wireless communication standards that require high-precision carrier frequencies, the design of D / A converters with high precision and low output noise is more difficult, and will use a large amount of layout area, increase additional power consumption, and thus increase costs

[0004] However, the simple method of digitally controlling the binary capacitor array, in the case of multi-bit switch jumps (such as changing from 01111111111111 to 10000000000000), due to the influence of parasitic capacitance, the frequency jump or non-monotonicity

This will seriously affect the frequency accuracy and the completion of automatic frequency control tuning

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