SA.45s Chip-Scale Atomic Clock
SA.45s CSAC User Guide Revision D
22
3. CSAC serial numbers are of the form YYMMCSXXXXX where YYMM is the year and month of
production and XXXXX is the serialized production unit number.
Table 7 • Status Codes of CSAC
Status
Acquisition Stage
9
Asleep (ULP mode only)
8
Initial warm-up
7
Heater equilibration
6
Microwave power acquisition
5
Laser current acquisition
4
Laser power acquisition
3
Microwave frequency acquisition
2
Microwave frequency stabilization
1
Microwave frequency steering
0
Locked
Note: If CSAC returns a status code other than shown in
set points. In this case, warm-up time takes longer than stated on the SA.45s datasheet. To avoid this, it
is recommended to always allow CSAC to remain powered on for >102 seconds after it acquires LOCK.
102 seconds is the minimum amount of time necessary to save CSAC set points to memory, thus
avoiding set-point re-acquisition upon its next power up.
Table 8 • Alarm Codes of CSAC
Alarm
Definition
Alarm Limit
0x0001
Signal contrast low
Contrast <1000
0x0002
Synthesizer tuning at limit
Synthesizer detuned from calibration by
>30 kHz or <–15 kHz
0x0004
Temperature bridge unbalanced
Bridge—set-point >±20 mV
0x0010
DC light level low
Set-point—DCL > 1.5 V
0x0020
DC light level high
DCL—set-point > 1.5 V
0x0040
Heater voltage low
<30 mV
0x0080
Heater voltage high
>2.48 V
0x0100
µW power control low
<20 mV
0x0200
µW power control high
>2.48 V
0x0400
TCXO control voltage low
<0.1 V
0x0800
TCXO control voltage high
>2.4 V
0x1000
Laser current low
<0.5 mA
0x2000
Laser current high
>2.3 mA
0x4000
Stack overflow (firmware error)
