Microchip Technology SA5 Series, Руководство пользователя

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Installation
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2019 Microchip Technology Inc. DS50002938A-page 19
2.2.1 Absolute Minimum and Maximum Ratings
Table 2-2 indicates the absolute minimum and maximum ratings to which the MAC can
be subjected without permanent unrecoverable damage.
TABLE 2-2: MINIMUM AND MAXIMUM RATINGS
Parameter Rating
Supply Voltage (V
CC
) 0VDC to +32VDC
1PPS Inputs –0.5V to +3.6V
Analog Tuning Voltage 0V to +5V (into 5 k Ω )
Maximum Current Draw
RS-232, BITE, Alarm: ±8 mA
RF output: ±8 mA
Storage Temperature –55°C to +100°C
Note: The MAC cannot be expected to perform normally when operated outside
of the recommended operating conditions noted on the product data sheet.
All ratings apply at +25°C, unless otherwise noted.
2.3 START-UP SEQUENCE
CAUTION
To avoid severe damage to the unit, do not apply power to the incorrect terminals. The
SA5X does not have reverse voltage protection.
When the MAC is initially powered on, it performs an acquisition sequence, which
includes stabilizing the temperature of the physics package, optimizing physics pack-
age operating parameters, and acquiring frequency lock to the atomic resonance.
A typical warm-up sequence is shown in
Figure 2-4 . When power is connected to the
MAC, its RF and 1PPS output signals (orange dashed line) will appear immediately.
The short-term stability specification of these signals will not be satisfied until the Lock
sequence is completed (after ~300 seconds in this example). Prior to Lock, the output
signal will have an inaccuracy of several ppm and drift per the MAC’s internal TCXO.
All MAC’s have their (Locked) output frequency calibrated to within ±5x10
-11
Hz/Hz
prior to shipment. However, environmental conditions and transit time will affect the cal-
ibration to an unknown degree. Therefore, some additional frequency offset should be
expected when the MAC is first powered on by the user. Offsets may be corrected, as
explained in the Frequency Steering section. The re-trace specification provides some
guidance for frequency offsets due to powering off the unit; however, the specification
is not comprehensive.
Power consumption is displayed as a solid black trace. Initially, the power consumption
will draw >10W to bring the internal unit temperature up to operational level. Once the
temperature has stabilized, the steady state power consumption will drop to ~6W.
Steady state power consumption will be higher for colder ambient temperatures
because more heating will be required to maintain the correct internal temperature.
Similarly, the duration of the heat-up period (maximum power consumption) will be lon-
ger for colder ambient temperatures.
The baseplate temperature (solid orange trace) will generally rise ~15°C during the
start-up sequence, but this varies greatly with thermal management (heat sink, airflow,
etc). Generally, the temperature rise will be smaller at warmer temperatures, larger at
colder temperatures.