AOCJY OCXO Vref

```AOCJY OCXO APPLICATION NOTE
REFERENCE VOLTAGE OUTPUT
Figure (1)
Vc (Control Voltage)
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1
R1
2
R2
5
GND
AOCJY OCXO
Vref
Vdd
5
TOP View
3
RF Output
4
GND
AOCJY OCXO
Vref
10k
1
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AOCJY devices also provide a Regulated DC output on
pin # 2 (Vref ). The value of this voltage is dependent
upon the Supply Voltage bias. For instance, for
Vdd = 5.0V; the Vref value will be +4.50V ±0.2V. Similarly for Vdd = 3.3V; the Vref value will be +2.80V ±0.2V.
Vc (Control Voltage)
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These devices are suitable for ROHS compliant reflow
and incorporate a Control Voltage (Vc) port; providing
a means to set these devices on frequency, post reflow.
Another way to achieve a similar result is to use a two
resistor – potential divider approach, as shown in
figure (2) below.
Figure (2)
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The AOCJY series of Oven Controlled Crystal Oscillators are designed to facilitate reference frequencies
from 10.00MHz to 100MHz carrier.
25.4 x 22.1 x 12.5 mm
2
Vdd
3
TOP View
RF Output
4
In this approach, the Vc Voltage will be given by:
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Vc = (R2 / (R1+R2)) * Vref
As depicted in figure (1), the simplest way to utilize the
Vref output is to connect a potentiometer between
Vref and Gnd. The “wiper” of the potentiometer
should then be connected to the Vc (Control Voltage
port) of the OCXO. This way, the DC Voltage value
@ Vc port can be adjusted by varying the position of
the wiper.
As shown, R2 can either be fixed or a variable resistor.
Good starting values for a 3.3V biased OCXO’s could be
R1= 6.98 kΩ and R2 = 10.00 kΩ
Similarly, for 5.0V biased OCXO’s, R1 = 8.06 kΩ and
R2 = 10.00 kΩ could yield the desired result. If a potentiometer is used in place of R2, the “wiper” should be
connected to the Vc port to provide variable resistance.
Please take note that the by-pass capacitors on both
the Vdd port, as well as the Vc port are merely
suggested values to help improve noise suppression.