EX-219 Datasheet, PDF (8/9 Pages) Vectron International, Inc – Hi-Reliability Evacuated Miniature Crystal Oscillator

EX-219
Hi-Reliability Evacuated Miniature Crystal Oscillator (EMXO)
a. Supply Ripple: With this option, an external LC filter with a
low current rating can be used in the Vosc line to
suppress supply ripple.
b. 3.3V LVCMOS Output: If 3.3V LVCMOS output waveform
is required and the 3.3Vdc supply does not have sufficient
power to operate the 3.3Vdc single supply option, then a
dual supply option with 5.0Vdc (Voven) and 3.3Vdc
(Vosc) can be used.
8. Thermal Considerations
The thermal resistance from the case of the EX-219 to the
mounting plate should be considered when the part is
mounted. Heat rise on the case is proportional to the steady
state power consumption shown in Figure 4. Since the oven
is a servo controlled system, the heat rise on the case will
eventually reach an equilibrium point depending on the
thermal resistance from the case to the mounting plate.
If the thermal resistance from the case to the mounting plate
is too high, the heat rise on the case will cause the oven to
shut off sooner.
In the event of oven shut off due to the case temperature
exceeding the oven set temperature, there is still remaining
self-heating power dissipated by the other components in the
oscillator circuitry. This self-heating power is 150 mW typical.
The EX-219 is a 16 pin doublewide dual in-line package
(DDIP). It consists of nine glass to metal seal feed-thru pins
and one case/GND pin. In space applications, sinking heat
through mounting pins is not recommended because the nine
feed-thru pins have poor thermally conductive properties.
Sinking heat directly from the case of the part to the mounting
plate is recommended.
9. Part Installation
Stress relief mounting is highly recommended for the EX-219.
Thermally conductive adhesive can be used to mechanically
bond the bottom surface of the case to the mounting plate with
all ten pins protruding through the clearance holes to the
opposite side of the PCB. Then, wires can be used to make
connections from the pins to the I/O pads on the PCB as
shown in Figure 8.
Figure 8
10. No Connection Pins
All "No Connection" pins are NOT electrically connected
internally and are recommended to be connected to GND.
11. Aging Projection
MIL-PRF-55310 specifies measurement of frequency aging
for 30 days or longer. The measurements obtained shall be fit
using the method of least squares to the function (1)
f(t) = A(ln(Bt + 1)) + fo
(1)
If the aging trend is not monotonic, the measurement period
shall be extended to 40 days or longer after the extremum in
the aging trend, and the measurements from 12 days after
the extremum is reached to the end of the aging
measurement period shall be fit to the above function. Thus,
Group B Aging can extend beyond 60 days.
To maintain Group B Aging to 30 days, the EX-219 uses a 3^rd
order log function (2) for non-monotonic aging trends.
f(t) = A+Bln(t) +Cln(t)^2 +Dln(t)^3 + fo (2)
Figure 9 shows that 40 days of aging data fit well to the 3^rd
order log function with R² greater than 99%. The fit function
was then used to project for one-year aging.
EX-219-10M0000
Rank 2 Eqn 8017 [UDF 3] y=3rd-Log(a,b,c,d)
r²=0.99761022 DF Adj r²=0.99756617 FitStdErr=0.17181463 Fstat=30334.605
a=6.2425414 b=0.66797883
c=3.5639266 d=-0.73843747
50
50
40
40
30
30
20
20
10
10
0
0
-10
-10
-20
-20
-30
-30
-40
-50
0
120
240
Time (day)
-40
-50
360
Figure 9
12. Leak Test
Most hermetically sealed packages are back filled with a gas
or gasses mixed with some low percentage of detective gas
such as He at around 1atm pressure and then are sealed
using resistance weld or seam weld methods. Packages
sealed in this manner have a typical leak rate of 1x10^-10 to
1x10^-9 atm cc/sec. Therefore, a leak detector having 1x10^-8
atm cc/sec resolution and accuracy will be sufficient to
perform the leak test.
On the other hand, the EMXO package is hermetically sealed
using a cold-weld process and evacuated under hard vacuum
during welding. The cold-weld package is typically used for
crystals and achieves a leak rate better than 1x10^-12 atm
cc/sec He. The internal vacuum level at seal is better than
1x10^-5 torr. To maintain performance over a mission life of 15
years, the EX-219 package leak rate should achieve 1x10^-11
Vectron International • 267 Lowell Road, Hudson, NH 03051 • Tel: 1-88-VECTRON-1 • http://www.vectron.com