VIAVI / GNSS Disciplined Oscillators
CSAC GPSDO

VIAVI CSAC GPSDO Chip Scale Atomic Clock GNSS Disciplined Oscillator Frequency Standard

GPS-disciplined frequency standard built on a chip scale atomic clock, with 10 MHz, 5 MHz and 1 PPS outputs and low-drift holdover.

Long-term oscillator aging
Less than 0.3 ppb per month in holdover without GPS; Zero aging with GPS
Frequency stability over temperature
Better than ±0.5E-09
1 PPS accuracy
±15 ns to UTC RMS (1-Sigma)
Frequency accuracy
Better than ±2E-010
Datasheet

Overview

The VIAVI CSAC GPSDO is a frequency standard that combines a Chip Scale Atomic Clock (CSAC) with a GPS receiver. When it has GPS lock, the receiver disciplines the atomic clock, so the unit shows zero long-term aging and its 1 PPS output is aligned to UTC. When GPS is not available, the CSAC keeps time in holdover with low aging.

The module has four isolated 10 MHz sine-wave outputs and one 5 MHz CMOS output through a distribution amplifier. It also has a CSAC flywheel-generated 1 PPS output that can be shifted relative to UTC in 1 ns steps. A TTL alarm output signals GPS unlock and hardware failure.

Receiver and control

The 50-channel GPS receiver supports SBAS (WAAS, EGNOS, MSAS) and works with passive or active L1 antennas. Its motion-adaptive filter settings switch automatically with vehicle velocity. The unit is controlled with SCPI-99 commands over RS-232 or USB, and it outputs NMEA 0183 sentences.

It runs on aircraft and vehicle power from 8 V to 36 V DC, or on 5 V through Mini-USB. It can also drive 16x2 LCD displays.

Key Features

  • Chip Scale Atomic Clock (CSAC) disciplined by GPS
  • Zero long-term aging with GPS lock
  • Less than 0.3 ppb per month aging in holdover without GPS
  • 1 PPS output adjustable in 1 ns steps relative to UTC
  • Four isolated 10 MHz sine wave outputs and one 5 MHz CMOS output
  • Full SCPI-99 control over RS-232 and USB
  • NMEA 0183 rev. 2.3 output sentences
  • 50-channel GPS receiver with WAAS, EGNOS and MSAS support
  • Motion-adaptive receiver filter with auto-sensing and auto-switching
  • TTL alarm output for GPS unlock and hardware failure
  • Aircraft and vehicle power range 8 V to 36 V DC, or 5 V via Mini-USB
  • Supports 16x2 LCD displays

Specifications

Frequency and Timing
Long-term oscillator aging Less than 0.3 ppb per month in holdover without GPS; Zero aging with GPS
Frequency stability over temperature Better than ±0.5E-09
CSAC only, no GPS Disciplining, 0°C to +70°C
1 PPS accuracy ±15 ns to UTC RMS (1-Sigma)
GPS Locked in Position Hold mode
Frequency accuracy Better than ±2E-010
after 3 minutes operation with GPS lock
Holdover stability <±2 µs over 24 Hour Period @+25°C
after 96 hours warmup; after 20 minutes with GPS lock
Warm up / stabilization time without GPS <3 min at +25°C to <5E-010 Accuracy Typical
ADEV (with GPS lock)
1 s <1E-10
10 s <2.5E-11
100 s <2E-11
1K s <1E-11
10K s <2E-12
Phase Noise
10 Hz -90 dBc/Hz
100 Hz -125 dBc/Hz
1 kHz -145 dBc/Hz
10 kHz -152 dBc/Hz
100 kHz -153 dBc/Hz
Outputs
1 PPS output (CSAC flywheel generated) 5 V CMOS output, can be shifted in 1 ns steps relative to UTC
10 MHz output, 5 MHz output Four Isolated 10 MHz Sine Wave +13 dBm ±3 dBm, one 5 MHz CMOS 5 V
Distribution amplifier port isolation, 2 MHz >98 dB
Distribution amplifier port isolation, 10 MHz >85 dB
TTL alarm output GPS Unlock and Hardware Failure indicator
GPS Receiver
GPS frequency, antenna L1 C/A 1574 MHz, Passive or Active Antenna 5 V, MMCX Connector
GPS receiver 50 Channels, Mobile, SBAS: WAAS, EGNOS, MSAS supported
Sensitivity, acquisition -144 dBm
Sensitivity, tracking -160 dBm
TTFF, cold start <45 sec
TTFF, warm start 1 sec
TTFF, hot start 1 sec
Motion adaptive filter settings Optimized depending on vehicle velocity (Auto-sensing, Auto-switching)
Interfaces
RS-232 control (including USB port) Full SCPI-99 Control Commands at 9.6 K, 19.2 K, 38.4 K, 57.6 K, 115.2 K
RS-232 NMEA output sentences NMEA 0183 rev. 2.3, Sentences: GGA, RMC, ZDA, PASHR, and others
USB, LCD support Optionally USB powered and controlled, supports 16x2 LCD Displays
Power
Supply voltage (Vdd) Aircraft and Vehicle Power Range: 8 V to 36 V DC, or 5 V via Mini-USB
Power consumption <1 W; <1.4 W with CMOS output option
12 V Vdd; datasheet prints "<1 W with CMOS output option (12 V Vdd) <1.4 W"
Environmental
Operating temperature -10°C to +70°C
Storage temperature -45°C to +85°C
g-sensitivity <0.2 ppb per-g per-axis
Magnetic sensitivity Less than 0.4 ppb per Gauss
MTBF >100,000 Hours
0°C to +70°C

Specifications are taken from the manufacturer's documentation. See the datasheet for complete and current values.

Applications

  • Mobile and vehicle-mounted timing
  • Airborne frequency reference
  • GPS holdover timing

Documents & Resources

CSAC GPSDO
datasheet · PDF