The design of a microcontroller temperature compensated crystaloscillator (ΜCTCXO) and automatic compensation line

摘要

A new concept in the design of the compensation circuit innmicrocontroller temperature compensated crystal oscillators (ΜCTCXO)nand the corresponding production line (ACL-automatic compensation line)nfor fully automatic oscillator calibration are presented. Thencommunications ability of ΜCTCXO is introduced to provide automaticncalibration. The shortened successive approximation calibrationnalgorithm gives a short calibration time and a reliable convergence ofnoscillator adjustment by the ACL system. The ΜCTCXO is realized as anlow-cost device encapsulated in a single cubic inch volume. Then±0.5 ppm frequency accuracy in the -40°C/+85°Cntemperature range is obtained by a 9-bit A/D converter, 10-bit D/A andn512 bytes of software placed in an EEPROM. The ACL system, in additionnto the standard laboratory frequency counter, temperature chamber and anPC host computer, requires only two additional boards: an analognmultiplexer board and an interface board. During production andnrecalibration, the ACL system can compensate many oscillatorsnsimultaneously in a single temperature run, without requiring componentnselection and human supervision