PIECEWISE LINEAR ANALOG TEMPERATURE COMPENSATION SCHEME UTILIZING A HIGHLY INTERACTIVE ELECTRICALLY PROGRAMMABLE READ-ONLY MEMORY
Original Publication Date: 1980-Aug-01
Included in the Prior Art Database: 2001-Oct-10
This paper describes an automatic learning system used for temperature compensation of crystal oscillators. The system has a learning mode in which it is subjected to the required environmental range and simultaneously receives an external signal to correct its output to the proper value. It contains an in- ternal sensor and an electrically programmable memory which permanently stores the correction quanti- ty for each step of the environmental variable (temperature in this case). When the learning process is completed, the system is switched to the operating mode and uses the proper correction quantity stored in the memory for each temperature that its sensor indicates. This approach should be useful in other ap- plications as well as temperature compensation. Its feasibility depends on being able to put the sensor, the correction circuits and the electrically programmable memory on an integrated circuit, The system outlined in the diagram (Figure 1) is intended primarily for oscillator temperature com- pensation where better than one part per million frequency stability is required from a relatively inexpen- sive quartz crystal. By utilizing a mix of analog compensation under digital control, smooth and con- tinuous maintenance of frequency over a wide temperature range is possible with the tailored oscillator- compensation EPROM interface programmed by on-chip logic.