Time base combiner module capable of automatically and seamlessly switching internal and external crystal oscillators

Abstract

The invention discloses a time base combining module for automatic seamless switching of internal and external crystal oscillators, which comprises an internal crystal oscillator XT1, an external crystal oscillator XT2, an electronic switch SPST1, an electronic switch SPST2, a combiner CMB, a reference level REF, a resistor R1, a resistor R2, a diode D1, a diode D2, a voltage comparator CMP1, a voltage comparator CMP2, a voltage comparator CMP3 and a power supply VCC. Loss of lock caused by jumping of reference signals is effectively solved, so that seamless switching of equipment is achieved, and stability of a system is guaranteed. According to the invention, the stability and no jump of the switching signal level can be ensured, and the simultaneous working time of the two crystal oscillators is very short and is at the nanosecond level, so that the stable and reliable operation of equipment can be ensured.

Description

technical field [0001] The invention relates to a time-base combination module for automatic and seamless switching of internal and external crystal oscillators. Background technique [0002] The crystal oscillator (crystal oscillator) is the clock reference of the equipment and the "heart" of the communication equipment. The constant temperature crystal oscillator with high stability and low phase noise is expensive and has a large volume. Due to cost constraints, the equipment often uses a lower level The crystal oscillator is used internally, and in order to facilitate the synchronization of multiple devices, the communication system often uses a high-performance or even a high-stable time base after GPS training as the unified clock of the entire system. Therefore, the device needs to have an external crystal input, that is, the device has internal, External crystal oscillator switching function. [0003] In the conventional way, the internal and external switching of t...

AI Technical Summary

Problems solved by technology

[0003] In the conventional way, the internal and external switching of the crystal oscillator will cause a short-term reference signal loss, which will cause the system clock interruption, and a short pause will cause fatal problems such as system out-of-synchronization, data loss, and communication interruption.

At the same time, after working for a long time, the quality of the internal crystal oscillator will decrease, which will also cause the same problem

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