SA.45s Chip-Scale Atomic Clock
SA.45s CSAC User Guide Revision D
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Figure 9 • CSACdemo Analog Tuning Panel
When analog tuning is enabled, the voltage present on pin 1 is displayed in the Analog Tuning field and
also reflected in the current reported value of steer on the main panel. To enable or disable analog
tuning, select
checkbox and click
.
Enable Analog Tuning
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3.3.12
Ultra-Low Power Operating Mode
The majority of the power in the CSAC is consumed by the physics package and microwave synthesizer.
In ultra-low power (ULP) mode, the physics package and synthesizer can be disabled for a user-specified
length of time, during which the CSAC operates as a free-running TCXO. Periodically, the atomic clock
portion of the CSAC is powered on (again for a user-specified amount of time) and the TCXO is re-
calibrated to the atomic frequency. Operating in this mode, the CSAC exhibits the short-term
performance of a TCXO with good long-term stability at significantly lower power compared to standard
mode. For example, if the atomic clock portion is only powered on for 5 minutes out of every hour (2
minutes for lock acqui 3 minutes of run time), then the time-averaged power of the CSAC may be
<30 mW.
Between calibration cycles, the CSAC in ULP mode exhibits the performance characteristics of a free-
running TCXO and therefore exhibits significantly higher short-term frequency drift and environmental
(temperature and vibration) sensitivity than a normally-operating CSAC. For this reason, ULP mode is
principally recommended only for applications that:
Require long-term timing performance, rather than short-term frequency or time stability.
Have a very stable environment (temperature and vibration).
Note: Due to the unique behavior and configurability of ULP, the datasheet performance specifications
for the SA.45s CSAC cannot be guaranteed while in ULP mode. The CSAC has short-term drift
performance of a low cost low performance TCXO. Contact Microsemi for additional assistance in
evaluating and optimizing ULP for your specific application.
The following illustration shows an example of a CSAC operating in ULP mode, with wake-time = 300 s (5
min) and sleep-time = 3300 s (55 min).
