AccuBeat NAC1 User manual

Document No. ZD24010
Rev. B2

Nano Atomic Clock
NAC1
User Manual
AccuBeat Ltd
5 Ha’Marpeh Str., Har Hotzvim
P.O. Box 45102, Jerusalem 91450
Israel

Document No. ZD24010 Rev. B2 NAC1 User Manual
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Change Record
Rev.
Description
Date
ECO No
Approved
A
Initial Revision
10-09-15
-
A.S
A6
Specification updated
11-09-16
-
A.S
B1
Specification updated
19-12-16
-
A.S
B2
Specification updated
29-04-18
-
C.L

Tel: [phone]
Fax: [phone]
E-mail: [e-mail]
Web: http://www.accubeat.com

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Warnings
Do not operate the unit before reading this manual.
To avoid electrostatic discharge (ESD) damage, proper ESD handling procedures must be
observed in unpacking, assembling, and testing the NAC1.
Warranty
•The Rubidium Frequency Standard purchased under your order is warranted for one
year against defects in material or workmanship.
•This warranty does not cover cases of inappropriate operation.
•Do not attempt to open the unit!
Before Cleaning
•Disconnect the product from the power before cleaning or maintenance.
General Notes
1. To avoid electric shock or fire hazard:
•Apply voltage to the connectors as specified in the product Electrical ICD
specifications.
•Do not connect the unit to power supply with reverse polarity.
•Operate this unit under dry conditions.
•Operate this unit in un-explosive atmosphere.
2. Use output load impedance of 1MΩ.
3. Use frequency corrections instruction with caution.
Uncontrolled corrections can cause the frequency accuracy to get out of calibration or
even cause the clock to be unlocked!
4. Solder: Hand solder using 63/37 Tin/Lead solder with maximum soldering tip
temperature of 330ºC (626ºF).
The information and specifications included in this manual are subject to change
without prior notice.
The information contained within this manual is the proprietary of AccuBeat Ltd.

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Table of Contents
1. General description .............................................................................................................. 6
1.1. Introduction .......................................................................................................................... 6
1.2. Key features ......................................................................................................................... 7
1.2.1. The NAC1’s main features ............................................................................................... 7
1.2.2. Special features................................................................................................................ 7
2. NAC1 Overview ................................................................................................................... 8
2.1. Precautions .......................................................................................................................... 8
2.2. Packaging ............................................................................................................................ 8
2.3. Absolute Maximum Ratings ................................................................................................. 8
2.4. Mechanical Interface and Mounting ..................................................................................... 9
2.5. Recommended Operating Characteristics ......................................................................... 10
3.Evaluation Kit .................................................................................................................. 11
3.1. Installing the NAC1 on the evaluation board ..................................................................... 11
3.2. Installing the NAC1 GUI software ...................................................................................... 12
3.3. Cabling ............................................................................................................................... 14
3.4. Evaluation Board Overview ............................................................................................... 14
3.5. Initial Start Up .................................................................................................................... 16
3.5.1. Initial Power-On.............................................................................................................. 16
3.5.2. Establishing Communication with NAC1........................................................................ 16
3.5.3. Basic NAC1 GUI Features ............................................................................................. 17
3.5.4. Frequency Tuning........................................................................................................... 18
4. Functional Description ....................................................................................................... 19
4.1. Principle of Operation ........................................................................................................ 19
4.2. Built-In Test (BIT) ............................................................................................................... 20
4.2.1. S/W indication................................................................................................................. 20
4.2.2. H/W indication ................................................................................................................ 20
4.3. 10 MHz Output Characteristics .......................................................................................... 21
4.4. Frequency Adjustments ..................................................................................................... 22
4.5. 1PPS Output ...................................................................................................................... 22
4.6. Rubidium free run .............................................................................................................. 23
4.7. Rubidium disciplined to 1PPS ........................................................................................... 23
4.8. 1PPS Input ......................................................................................................................... 23
5. Disciplining Mode ............................................................................................................... 24
6. Appendices ........................................................................................................................ 26
Appendix A: Mechanical ICD...................................................................................................................... 26
Appendix B: Electrical ICD.......................................................................................................................... 27
Appendix C: Software ICD (CLI)................................................................................................................. 28
Appendix D: Specifications......................................................................................................................... 35

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List of Figures
Figure 1 : NAC1 Mechanical drawing and Pinout ..............................................................................................9
Figure 2 : Protective sheet for Evaluation Board .............................................................................................11
Figure 3 : NAC1 on Evaluation board.............................................................................................................12
Figure 4: LabVIEW85RuntimeEngineFull installation......................................................................................13
Figure 5 : visa441runtime installation .............................................................................................................13
Figure 6 : Evaluation Board Connections........................................................................................................14
Figure 7: NAC1 GUI Software.......................................................................................................................16
Figure 8 : NAC1 Block Diagram.....................................................................................................................20
Figure 9 : BIT LED indication.........................................................................................................................21
Figure 10 : NAC1 10MHz Output Driver .........................................................................................................21
Figure 11 : Evaluation Board 10MHz Output Driver.........................................................................................22
Figure 12 : Mechanical ICD...........................................................................................................................26
List of Tables
Table 1: Absolute Maximum Ratings................................................................................................................8
Table 2 : Recommended Operating Characteristics ........................................................................................10
Table 3: Electrical ICD .................................................................................................................................27
Abbreviations
1PPS –1 Pulse Per Second
BIT - Built In Test
CLI –Command Line Interface
DAC –Digital to Analog Converter
H/W - Hardware
TCXO –Temperature Compensated Crystal Oscillator
P/N –Part Number
S/N –Serial Number
S/W –Software
I/O –Inputs/Outputs
Rb –Rubidium

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1. General description
1.1. Introduction
AccuBeat's 1st generation Nano-Atomic-Clock (NAC1) is an ultra-small, ultra-low power Rubidium Atomic
Clock. NAC1 utilizes a modulated miniature diode laser to optically pump a miniature Rubidium glass cell.
The modulation frequency is derived from a local crystal oscillator which is then locked to the Rubidium
atomic line, thereby delivering the high stability of the atomic quantum transition to NAC1 outputs at
10MHz and 1PPS.
The small size and low power consumption of the NAC1, enables atomic timing accuracy in various
applications such as: GPS receivers, UAV’s, Autonomous sensors and Backpack secure communication
radios.
This manual provides technical guidance to facilitate mechanical, electrical, and functional integration of
the NAC1.
This manual also describes the NAC1 Evaluation Kit (AccuBeat P/N: AA50766), which includes an
evaluation board, cabling, and the NAC1 Graphic User Interface (GUI) software.
Installation and use of the NAC1 Evaluation Kit is presented in Section 3 of this User Manual. The
description of NAC1 functionality in Section 4 includes examples from the Evaluation Kit.

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1.2. Key features
1.2.1. The NAC1’s main features are as follows:
Input: 1PPS (for disciplining).
Outputs:
•Main frequency output (10MHz).
•1PPS
Medium term stability: 2E-11 @ 100s.
Phase noise: <-148 dBc/Hz @ 100 KHz (relative to the main 10MHz output).
Size: 32cc (41.1mm X 35.3mm X 22 mm)
Weight: ≤75 grams.
Communication: RS-232 (CMOS 3.3V, 1MΩ).
Power supply: 3.3VDC
1.2.2. Special features:
•Disciplined to 1PPS: The NAC1 is disciplined to a 1PPS signal, which improves the long-term-
stability as well as the accuracy.
.

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2. NAC1 Overview
2.1. Precautions
Do not operate the unit before reading this manual.
To avoid electrostatic discharge (ESD) damage, proper ESD handling procedures must be
observed in unpacking, assembling, and testing the NAC1.
2.2. Packaging
Please retain the original NAC1 ESD-safe packaging material in the event that the device needs to be
returned to AccuBeat for service.
2.3. Absolute Maximum Ratings
Table 1 indicates the absolute maximum ratings to which the NAC1 can be subjected without
permanent unrecoverable damage. Note that the NAC1 cannot be expected to operate normally when
operated outside of the Recommended Operating Conditions (Table 2) and no performance is
guaranteed under absolute maximum ratings.
All ratings apply at 25°C, unless otherwise noted.
Rating
Parameter
4.1 V
Supply Voltage (Vcc)
1PPS in, Tx, Rx, BIT: +/- 2 mA1PPS out, 10 MHz out: +/- 20 mA
Maximum current draw
-40°C to +90°C
Storage Temperature
Table 1:Absolute Maximum Ratings

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2.4. Mechanical Interface and Mounting
The physical dimensions of the NAC1 are 1.62” x 1.41” x 0.87” H.
Detailed dimensions and NAC1 Pinout are shown in Figure 1.
Pin # 3 is not present in the NAC1.
For initial testing and evaluation it is recommended that the pins should not be modified or soldered to a
PCB. The recommended socket for connecting the PCB is SAMTEC P/N: SC-2P7-TT or SC-2P7-GG.
When soldering the NAC1 to a PCB, please notice that the bottom surface of the NAC1 will be
parallel to the PCB in order to prevent electrical shortages.
Figure 1 : NAC1 Mechanical drawing and Pinout

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2.5. Recommended Operating Characteristics
The NAC1 pinout is shown above in Figure 1. The electrical function of each pin is defined in this section.
Refer to the Reference Section for a detailed functionality description of each pin.
PIN #
NAME
FUNCTION
VOLTAGE LEVELS
NOTES
REFERENCE
SECTION
1
N/C
Not Connected
2
GND
Ground
-
-
-
3
N/A
Not Applicable
4
BIT
Built-In Test
2.5 V < Logic H < Vcc0 V < Logic L < 0.5 V
1,5
4.2
5
Tx
Comm. Transmit
2.5 V < Logic H < Vcc0 V < Logic L < 0.5 V
5
Appendix C:
Software ICD
(CLI)
6
Rx
Comm. Receive
6
7
Vcc
Input Voltage
3.3 VDC +/- 0.1 VDC
4
8
GND
Ground
9
1PPS IN
1 Pulse Per Second
Input
2.5 V < Logic H < Vcc0 V < Logic L < 0.5 V
2,6
4.8
10
1PPS OUT
1 Pulse Per Second
Output
2.5 V < Logic H < 2.85 V0 V < Logic L < 0.5 V
2,3,5
4.5
11
Fact. Use
Factory Use
-
12
10MHz OUT
10MHz Output
2.5 V < Logic H < Vcc 0 V < Logic L < 0.5 V
5
4.3
Table 2 : Recommended Operating Characteristics
Notes:
1. Built-in Test (BIT) output:
0: Normal Operation
1: Unlocked
2. Timing reference is the rising edge of an input pulse.
3. Output 1PPS is 20μs in duration.
Timing reference is the rising-edge of Pin # 10. Rise time < 10 ns.
4. Regulated 3.3V DC.
Recommended regulator : MICREL P/N: MIC39100-3.3WS
5. Load Impedance = 1MΩ.
6. Input Impedance = 1MΩ.