OCXO Datasheet, PDF (2/7 Pages) MICORO CRYSTAL SWITZERLAND – Oven Controlled Crystal Oscillator

Application Note
Employing a proportionally controlled oven can improve oscillator temperature stability relative to the crys-
tal’s inherent stability by more than 5000 times (from ±1x10^-5 to ±1x10^-9 over 0-50°C, for example). However,
the oven control system is not perfect because (a) the open loop gain is not infinite, (b) there are internal
temperature gradients within the oven and (c) circuitry outside the oven which is subjected to ambient tem-
perature changes can “pull” the frequency. Therefore, a change in ambient temperature will result in small
changes in oven temperature.
Setting Oven Temperature
Figure 2.
X
(1)
(2)
Y
Temperature
A
B
C
D
As shown above, the actual temperature to which the oven is set is critical in minimizing the effect of ambi-
ent temperature change.
Referring to Figure 2, if the oven temperature were set to the point designated as (1), and a change in am-
bient temperature caused a change in oven temperature from A to B, a frequency change of magnitude X
would result. However, if the oven temperature were set to the upper turnover point (2), an equal tempera-
ture change (C to D) would result in a significantly reduced change in frequency (magnitude Y). Therefore,
each Vectron oven is individually set to the turnover temperature of the crystal which it houses. This is ac-
complished by adjusting the potentiometer shown as one leg of the bridge in Figure 1.
Vectron International • 267 Lowell Road, Hudson, NH 03051 • Tel: 1-88-VECTRON-1 • http://www.vectron.com
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