www.microchip.com
Frequency and Timing
SA.31m, SA.33m, and SA.35m
Miniature Atomic Clock (MAC) SA.3Xm
Features
• High-precision atomic clock
• Small form factor (standard OCXO
pinout)
• 1.5 μs typical holdover over
temperature (SA.35m)
• Low power consumption
• RoHs 6/6-compliant
Applications
• Stand-alone (free-run) stable fre-
quency source for audio equipment,
LTE base stations, smart grid, and
enterprise network Infrastructure
• Extended holdover for CDMA and
WiMAX base stations
• Stability for various other communica-
tion and transmission applications
Newly Enhanced MAC SA.3Xm
Family
The Microchip SA.3Xm marks a major
step forward in the evolution of rubidium
atomic clocks. Based on a new gen-
eration of atomic clock technology, the
SA.3Xm family has a unique package
that enables unprecedented miniaturiza-
tion in a rubidium clock. It is suitable for
applications requiring compact design,
low power consumption, low aging, and
precision in an economical and easily
adaptable package.
Smallest Commercially
Available Rubidium Clock
Microchip has leveraged the signicant ad-
vances in miniaturization and integration to
design the world's rst commercially avail-
able miniature atomic clock. The SA.3Xm
has physical dimensions and packaging of
a small ovenized crystal oscillator (OCXO),
measuring 50.8 mm x 50.8 mm (2" × 2")
and standing at a mere 18.3 mm (0.72").
The MAC is the world’s rst commercially
available rubidium coherent population
trapping atomic clock. It consumes less
power and has wide spectrum tempera-
ture operation. This makes it useful for a
range of timing and synchronization ap-
plications—wireless base stations, wire line
network infrastructure, defense systems,
and test and measurement devices. The
small size of the SA.3Xm enables it to be
easily mounted to a PCBA.
SA.31m
The SA.31m is targeted for applications
that require an economical solution for
frequency stability, such as audio equip-
ment in studio applications. It can also
be used as an independent frequency
source for next generation base stations,
smart grid infrastructure and Enterprise
network infrastructure. It enables
transition from costly TDM backhaul
transport to economic and ecient
Ethernet transport.
SA.33m
The SA.33m has superior aging,
tempco, and stability than the SA.31m.
The SA.33m may be deployed in existing
rubidium applications such as ex-
tended holdover (for CDMA/CDMA 2000
or WiMAX).
SA.35m
The SA.35m is the premium grade of
the entire SA.3Xm family. It has the
best tempco and greatest performance
amongst all the versions of the family.
The SA.35m is suited for applications
such as extended hold over for LTE-TDD
base stations and other applications that
require precision frequency and long
hold-over. Economical for its perfor-
mance level, the SA.35m delivers pre-
mium performance at an excellent price.
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Specications1
Electrical
RF Outputs
Frequency 10 MHz
Waveform CMOS square wave,
0 VDC–5 VDC(max)
Logic Level VOL(max) 0.55 V, VOH(min) 2.3 V
Rise/Fail Time <10 ns (15 pf, 1MΩ load)
Duty Cycle 50% ± 10%
Built-in Test Equipment Output
Format CMOS
Logic 0 = Normal Operation
1 = Alarm
Serial Communications
Protocol RS232
Format CMOS 0 V to 5 VDC
Baud Rate 57600 (8, N, 1)
Power Input
Supply Voltage/Current 5 VDC ± 0.1 VDC, max current <2.8 A
Power Consumption
Warm-up 14 W max (–10 °C to 75 °C)
Operating 8 W at 10 °C, 5 W at 25 °C,
5 W at 75 °C baseplate
Voltage Coecient <2 × 10–11 peak-to-peak
(+5 VDC ± 0.1 VDC)
1At 25 °C and 5 VDC, unless otherwise specied.
Environmental
Specication
Operating Temperature –10 °C to 75 °C baseplate
Magnetic Sensitivity <±7 × 10–11/Gauss (up to±2 Gauss)
Humidity GR-63-CORE, issue 4,
April 2012, section 4.1.2
Vibration
(Operating)
7.7 grms, at 1 hour/axis
MIL-STD-810, gure 514.7E-1, category 24
(General Minimum Integrity Exposure)
No loss of lock
Humidity Shock
(Operating)
30 g, 11 ms half-sine pulse per MIL-STD-202,
Method 213, Test Condition J. Frequency
perturbation ≤4 × 10– 9 momentary
Storage and Transport (Non-operating)
Temperature –55 °C to 100 °C
Vibration
(non-operating,
unpackaged)
10.9 grms at 1 hour/axis per MIL-STD-810,
gure 514.7E-1, Cat 24
Shock
(non-operating,
unpackaged)
50 g, 11 ms half-sine pulse per MIL-STD-202,
Method 213, Test Condition A
Performance Parameters
Specication
Warm-up Time
(Time to <1 × 10–9)
Retrace <±5 × 10–11
(on-o-on: 24 hours, 48 hours, 12 hours)
Analog Tuning Range: ±1 × 10–8
Input: 0 V–5 V into 5 kΩ
Digital Tuning Range: ±2 × 10–8
(resolution ±1 × 10–12)
Time Drift in a 24 hr Period
(SA.35m) 1.5 μs, typical (–10 °C to 70 °C, 16 °C/hr)
MTBF
Per MIL-HDBK-217F ≥20 years at 40 °C (ground, benign, GB)
≥17 years at 40 °C (ground, xed, GF)
Per Telcordia SR-332,
Issue 1
≥20 years at 40 °C (ground, xed,
uncontrolled)
Accuracy at Shipment <±5 × 10–11
<15 min (typical @25C)
www.microchip.com
Phase Noise (SSB)
Frequency Sa.35m/SA.33m SA.31m
1 Hz <–70 dBc/Hz <–65 dBc/Hz
10 Hz <–87 dBc/Hz <–85 dBc/Hz
100 Hz <–114 dBc/Hz <–112 dBc/Hz
1 kHz <–130 dBc/Hz <–130 dBc/Hz
10 kHz <–140 dBc/Hz <–140 dBc/Hz
Spurious (non-harmonic) <–85 dBc
Temperature Coecient (Peak-to-Peak)
Temperature SA.35m SA.33m SA.31m
0 °C to 70 °C ≤7 × 10–11 ≤1 × 10–10 ≤7 × 10–10
–10 °C to 75 °C ≤1 × 10–10 ≤1.5 × 10–10 ≤1 × 10–9
Aging
Type SA.35m/ SA.33m SA.31m
Daily2±2.5 × 10–11 ±4 × 10–11
Monthly2±1 × 10–10 ±3 × 10–10
Yearly ±1 × 10–9 ±1.5 × 10–9
2After 1 day and 1 month of operation, respectively.
Short-Term Stability (Allan Deviation)
Type SA.35m/ SA.33m SA.31m
τ = 1 s ≤3 × 10–11 ≤5 × 10–11
τ = 10 s ≤1.6 × 10–11 ≤2.5 × 10–11
τ = 100 s ≤8 × 10–12 ≤1 × 10–11
Physical
Specication Details
Weight <85 g (<3 oz)
Size 18.3 mm × 50.8 mm × 50.8 mm
Volume <49.5 cm3 (< 3.0 in3)
RoHS Compliance
6/6 RoHS-compliant
Ordering Information
Part Number Description3
090-44310-31 SA.31m Rubidium Clock, AT Disabled
090-44310-32 SA.31m Rubidium Clock, AT Enabled
090-44330-31 SA.33m Rubidium Clock, AT Disabled
090-44330-32 SA.33m Rubidium Clock, AT Enabled
090-44350-31 SA.35m Rubidium Clock, AT Disabled
090-44350-32 SA.35m Rubidium Clock, AT Enabled
090-44300-00 SA.3Xm Developer's Kit
3AT = Analog Tuning
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companies.
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