ULN-2550 GPS Disciplined Oscillator (GPSDO) DOCXO Module with 10, 25/50 and 100 MHz Outputs

Compact GPS disciplined oscillator board with 10 MHz, 25/50 MHz LVDS and 100 MHz outputs, built for low-phase-noise up-conversion.

1 PPS Accuracy: ±30 ns to UTC RMS (1-Sigma)
Frequency Accuracy: Better than ±3E-010
Holdover Stability: <±7 µs over 24-Hour Period
ADEV: 1 s to 1000 s: <5 E-11

Datasheet

Overview

The VIAVI ULN-2550 is a very small GPS Disciplined Oscillator (GPSDO) that serves as a time, frequency and position reference. It is designed for up-conversion applications that need 10 MHz, 25 MHz, 50 MHz and/or 100 MHz sources. The 10 MHz and 100 MHz outputs are always available. The 25 MHz output can be changed to a 50 MHz output with stuffing options.

The module is built around a high-end SC-cut Double Oven Crystal Oscillator (DOCXO) and a 50-channel GPS receiver with -160 dBm tracking sensitivity. It provides four 25/50 MHz LVDS outputs, one 100 MHz CMOS output, one 10 MHz CMOS output and 1 PPS outputs. A WAAS/EGNOS/MSAS-capable GPS receiver disciplines the oscillator under the control of a 32-bit processor. A hold-over mode compensates for aging and temperature.

Apart from the GPS antenna connection, all I/O and power input share one connector. That connector can be a board-to-board interface or a cable harness, which simplifies system integration and supports stringent military requirements.

All outputs are frequency- and phase-synchronized to UTC through GPS, giving Better-Than-Cesium™ long-term performance. The unit is controlled over RS-232 with standard SCPI commands, and settings are stored in non-volatile memory. It is compatible with the GPSCon Windows graphing and SNTP server software. Typical uses are ultra-low-phase-noise up-conversion systems in radar and satellite communication equipment.

Key Features

10 MHz, 25 MHz/50 MHz, and 100 MHz outputs with 4x LVDS
Typical Allan Deviations of <5E-11 with GPS lock for measurement intervals from 1 to 1000 s
Phase noise of <125 dBc at >10 Hz offsets is standard
Power consumption of <4 W with DOCXO at 25°C
High-end WAAS/EGNOS/MSAS GPS receiver drives an ultra-stable OCXO frequency reference under the control of a 32-bit processor
High-end SC-cut Double Oven Crystal Oscillator
50-channel GPS receiver with -160 dBm tracking capability
Hold-over mode with aging and temperature compensation
Alarm outputs
RS-232 control using standard SCPI commands
Settings automatically stored in non-volatile memory
Sine Wave, CMOS, and LVDS outputs
All I/O and power input on a single connector (board-to-board or cable harness), except the GPS antenna
Outputs frequency- and phase-synchronized to UTC via GPS
GPSCon Windows graphing and SNTP server software compatible

Specifications

Module Specifications

1 PPS Accuracy	±30 ns to UTC RMS (1-Sigma) GPS Locked
Frequency Accuracy	Better than ±3E-010 after 1 hour operation with GPS locked
Holdover Stability	<±7 µs over 24-Hour Period @+25°C (No Motion, after 5 days with GPS)
ADEV	1 s to 1000 s: <5 E-11 with GPS lock typical
Warm Up Time/Stabilization Time	<10 min at +25°C to 1E-09 Accuracy Typical
Supply Voltage (Vdd)	11.0 V to 16.0 V DC Nominal
Power Consumption	<4 W at +25°C with DOCXO
Environmental Conformance	MIL-STD-202, Method 204, Condition I-A

Outputs and Control

1 PPS Outputs (OCXO Flywheel Generated)	Two outputs: 5 V CMOS and LVDS Web page lists a 1 PPS LVDS output; datasheet lists both CMOS and LVDS
10/25/100 MHz Outputs (6x total, 4x @25/50 MHz, 10 MHz, 100 MHz)	4x LVDS 25/50 MHz, 1x CMOS 100 MHz, 1x CMOS 10 MHz
RS-232 Control	TTL Level, Full control via SCPI-99 Control Commands, NMEA 0183 TTL Level, RS-232 levels optional
TTL Alarm Output	GPS Unlock and Hardware Failure indicator

GPS Receiver

GPS Frequency	L1, C/A 1574 MHz
GPS Antenna	Passive or Active, 5 V
GPS Receiver	50 Channels, Mobile, GPS, WAAS, EGNOS, MSAS supported, Galileo ready
Sensitivity, Acquisition	-144 dBm
Sensitivity, Tracking	-160 dBm
GPS TTFF, Cold Start	<45 sec
GPS TTFF, Warm Start	1 sec
GPS TTFF, Hot Start	1 sec

Oscillator Specifications

Frequency Output	10 MHz, 25/50 MHz, and 100 MHz outputs
10/100 MHz Retrace without GPS	±2E-08 After 1 Hour
Frequency Stability	±2.5E-010 over temperature low-g option: ±3E-010 per g per axis
Output Amplitude, 10 MHz	CMOS 5V
Output Amplitude, 25/50 MHz	LVDS
Output Amplitude, 100 MHz	CMOS 3.3V
Warm Up Time	<12 min Oscillator specification; module warm-up/stabilization time is listed as <10 min to 1E-09
Designed Lifetime	>10 years

Phase Noise

1 Hz offset, 25 MHz Out	-88 dBc/Hz
1 Hz offset, 10 MHz Out	-100 dBc/Hz
10 Hz offset, 25 MHz Out	-109 dBc/Hz
10 Hz offset, 10 MHz Out	-125 dBc/Hz
100 Hz offset, 25 MHz Out	-125 dBc/Hz
100 Hz offset, 10 MHz Out	-142 dBc/Hz
1 kHz offset, 25 MHz Out	-145 dBc/Hz
1 kHz offset, 10 MHz Out	-152 dBc/Hz
10 kHz offset, 25 MHz Out	-155 dBc/Hz
10 kHz offset, 10 MHz Out	-155 dBc/Hz
100 kHz offset, 25 MHz Out	-160 dBc/Hz
100 kHz offset, 10 MHz Out	-155 dBc/Hz

Environmental

Operating Temperature	-25°C to +75°C
Storage Temperature	-45°C to +85°C

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

Applications

Ultra low-phase-noise up-conversion systems
Radar equipment
Satellite communication equipment
Defense
5G communications
SATCOM
Transportation
Data center
Energy
Financial
Critical infrastructure

Options & Accessories

Option	Description
1002501-G2	ULN 2550 25MHz SOCXO GPSDO OEM Board - non-RoHS
22174855	ULN 2550 25MHz SOCXO GPSDO OEM Board - RoHS
22174860	ULN 2550-G2 50MHz SOCXO - RoHS
22174861	ULN 2550-G2 50MHz SOCXO RS232 - RoHS
1001026-ST-G2	ULN-2550 25MHz DOCXO Ruggedized EC GPSDO OEM Board Low G - non-RoHS
22174845	ULN-2550 25MHz DOCXO Ruggedized CC GPSDO OEM Board Low G - RoHS