INFICON PLO-10i Phase Lock Oscillator - Manual (Page 33)

PLO-10 PHASE LOCK OSCILLATOR
CALCULATING CRYSTAL POWER 6-1
6 CALCULATING CRYSTAL POWER
Using the PLO conductance voltage output, crystal power can be calculated. Refer to
Section 3 CALCULATING CRYSTAL RESISTANCE, crystal resistance, R
cry,
is given
as (100/ V
cond
)-20, where V
cond
= Conductance Voltage.
Crystal power, P
cry
= i 2 * R
cry
Since i
cry
= V
soc
/(20 + R
cry
) or (V
cond
/100) * V
soc
Hence, P
cry
= i 2 * R
cry
= [(V
cond
/100) * V
soc
] 2 * [(100/ V
cond
)-20]
P
cry
= V
soc
2 * (V
cond
/100) * [1-20(V
cond
/100)]
V
soc
= Voltage of source open circuit = 125 mV (open circuit source voltage crystal drive)
Then, P
cry
= 0.125 2 * (V
cond
/100) * [1-20(V
cond
/100)]
Examples:
1.
Conductance output voltage = 1.000 volt
P
cry, in watts
= 0.125 2 * (1/100) * [1-20(1/100)] = 1.25E -4 watts or 125 µW
2. Conductance output voltage = 0.015 volts
P
cry, in watts
= 0.125 2 * (0.015/100) * [1-20(0.015/100)] = 2.3E -6 watts or 2.3 µW
Crystal Power vs. Conductance Voltage
0.0
50.0
100.0
150.0
200.0
250.0
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
2.2 2.4 2.6 2.8
3
3.2 3.4 3.6 3.8
4
Conductance Voltage (volts)
Cryst
al Power (
uW)
Figure 8 Crystal Power Dissipation vs. Conductance Voltage