Multi-modulus programmable frequency divider structure with counter directly controlling phase switching

Abstract

The invention discloses a multi-modulus programmable frequency divider structure with a counter directly controlling phase switching. The structure comprises a N / N+1 phase switching type dual-modulus prescaler, a programmable counter P and a pulse-swallow counter S, wherein a prescale signal F<pre> output by the N / N+1 phase switching type dual-modulus prescaler is used as a work clock of the programmable counter P and the pulse-swallow counter S at the same time, a frequency divided signal F<out> output by the programmable counter P is used as total output of the multi-modulus programmable frequency divider structure, and a reset signal output by the programmable counter P is used as the reset signal of the programmable counter P and the pulse-swallow counter S at the same time. Compared with the conventional structure, in the structure provided by the invention, an independent prescale mode control signal MC and a phase selection logical circuit are eliminated, influence of time delay of the phase selection logical circuit on a switching window is directly eliminated, thus, the prescaler is restrained from outputting glitch, and correct frequency division is guaranteed when performing phase switching.

Description

technical field [0001] The invention relates to integrated circuit technology, in particular to the technology of a phase-switching frequency divider, in particular to a multi-mode programmable frequency divider structure in which a counter directly controls phase switching. Background technique [0002] The frequency divider is located in the feedback loop of the phase-locked loop. Its function is to divide the high-frequency signal output by the oscillator to a lower frequency with a specified frequency division multiple, and compare it with the reference clock. The programmable frequency divider is the most widely used frequency division circuit. It consists of a dual-mode prescaler, a programmable counter, a pulse swallow counter and a control logic circuit. The phase switching structure is a typical dual-mode prescaler. structure. In the phase switching dual-mode prescaler, the time window of the phase switching action needs to be carefully selected. Only when the leve...

AI Technical Summary

Problems solved by technology

In the phase switching dual-mode prescaler, the time window of the phase switching action needs to be carefully selected. Only when the level of the original signal at the moment before the switching action is consistent with the level of the new signal at the moment after the switching action, can the phase be guaranteed. The switching is correct to achieve N+1 frequency division, otherwise the output signal of the multiplexer will produce glitches, resulting in frequency division errors

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