Microchip Technology SA5 Series, Руководство пользователя

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MAC-SA5X User’s Guide
DS50002938A-page 20
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2019 Microchip Technology Inc.
Care should be used to ensure that the maximum operating temperature is not violated.
For instance, a MAC that is powered up in a 70°C ambient environment will likely rise
above the maximum operating temperature during the start-up period unless careful
thermal management is employed. (See
Section 2.2 “Mounting Considerations” )
The
LockProgress
parameter (not pictured) will reveal the Lock acquisition status in
terms of percentage-complete. Once the unit finishes the sequence, the BITE pin
(black dashed trace) will indicate Lock (logic low). Generally, Lock acquisition times will
be shorter at warmer temperatures, longer at colder temperatures. If this sequence
should fail, the
Alarms
parameter will signify “Acquisition Failed”. If this should occur,
check that the environmental specifications have not been violated (operating tempera-
ture, input voltage, magnetic field exposure, etc) and reboot the device. Contact Cus-
tomer support if the alarm persists.
Note: Sequence times and power levels vary according to environmental condi-
tions, especially temperature.
FIGURE 2-4: Start-Up Sequence.
Once power is supplied to the unit, it will output the following strings on the serial port:
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[>Microchip SA5X]
After a typical warm-up time of 5 to 7 minutes, the oscillator is fully operational and the
operator may choose to adjust the device parameters. The MAC meets all short-term
stability specifications as soon as Lock is achieved. Long-term stability specifications
(Monthly Aging frequency drift rate) is satisfied within 30 days of continuous power at
room temperature. There are no maintenance procedures or adjustments needed,
aside from frequency adjustment which is described in a later section.