Module Data Sheet: VCT2000A 155.520MHz
Application: LVPECL Output-Dual Input Clock Generator
Page 1 of 5 Rev. “7” 6/02/03
1.0 DESCRIPTION AND APPLICATION
The VCT2000A is a dual reference input 3.3V clock generator module with an
HCMOS output. Reference inputs are selectable by a one-bit select control input.
An alarm output can be used to detect a problem on the selected reference, such as
a loss of lock or a loss of reference. A logic level “1” is indicated from the alarm pin
when there is a problem with the selected reference. The unit operates in the free run
mode when there is a problem with the selected reference, or when free run is invoked by
enabling the forced free run input. Free run accuracy will keep the output to within 20
ppm. The reference will not automatically switch upon loss of reference. Also, all
outputs may be tri-stated for external testing purposes with a signal to the Tri-State/Reset
input.
The Loss of Reference alarm detects a missing rising edge within 100 nS of the
missing edge. This is usually around 70 nS.
The 8kHz output is divided from the on-board low jitter oscillator. Output phase
coherence is maintained during reference switching rearrangement, so the output phase
will not necessarily be the same as the reference being used.
The dimensions of the low jitter module are 1.00” x 1.05” x 0.32” mounted on a
FR-4 board with castillations.
FEATURES:
• Output jitter below 1 ps from 12 kHz to 20 MHz
• Two Selectable References @ 8 kHz
• Alarm Output Detecting Loss of Reference or Loss of Lock
• Tri-State-able Outputs
• Force Free-Run Function
• Automatic Free Run Operation upon loss of both references
• Rising Edge Phase Detector allows for any Duty Cycle Reference Input
• 3.3 Volt Regulated Powe r Supply
• Small Size: 1 in (25.40 mm) X 1.05 in (26.67 mm) X 0.32 in (8.13 mm)
• Surface Mount with Castillated Pins
Module Data Sheet: VCT2000A 155.520MHz
Application: LVPECL Output-Dual Input Clock Generator
Page 2 of 5 Rev. “7” 6/02/03
ALIGNER
8 KHz
REF A
SEL AB
ENABLE / TRISTATE
REF B PHASE
FORCE FR EE RUN
LOW PASS
DET
PHASE
f / N
FILTER
ANALOG LOW Q
VCXO
JITTER
OPTIONAL
REFERENCE
OUTPUT
Q
ALARM
FREE RUN STATUS
VCT2000A Block Diagram
2.0 ELECTRICAL CHARACTERISTICS
Specification Min Typ Max Units
2.1 Regulated Input Supply Voltage, Vcc 3.10 3.30 3.50 V DC
2.2 Supply Current Drain @ 3.5Vdc 110 mA
2.3 Frequency Output 155.520 MHz
2.4 Temperature Ranges
2.4.1 Operating Temp. Range 0 70 ºC
2.4.2 Storage Temp. Range -40 85 ºC
2.5 Timing Parameters
2.5.1 Output Rise and Fall Time (20% 80%) - - 550 ps
2.5.2 Input Jitter Tolerance @ 8kHz Reference
(Input Jitter Frequencies > 10 Hz) 31.25 - - µs
2.5.3 Acquisition Time (Offsetting reference by 20ppm) - 1 - s
2.5.4 J itter Filter Bandwidth - - 10 Hz
2.5.5 Capture/pull-in range -25 - 25 ppm
2.5.6 Free Run Frequency -20 - 20 ppm
2.5.7 Output Duty Cycle 45 50 55 %
2.5.8 Phase Transient due to Reference switching 150 nS
2.5.9 SONET Jitter BW 12 kHz - 20 MHz 1 ps
2.6 Input Logic Levels
2.6.1 ‘ 0’ -0.5 0.8 V
2.6.2 ‘1’ 2.4 5.5 V
2.7 Output Logic Levels (into 50Ω @Vcc-2.0V)
2.7.1 ‘0’ Vcc-1.62 V
2.7.2 ‘1’ Vcc-1.02 V
Module Data Sheet: VCT2000A 155.520MHz
Application: LVPECL Output-Dual Input Clock Generator
Page 3 of 5 Rev. “7” 6/02/03
2.8 Dual Reference input (+/- 30ppm) 8 kHz
2.9 Output loads @ Vcc-2.00V 50 Ω
3.0 MECHANICAL CHARACTERISTICS
Pkg. size is 1 in (25.40 mm) X 1.05 in (26.67 mm) X 0.32 in (8.13 mm) max on an FR4 board
with castellated pins. Overall coplanarity is .004 in (0.101mm).
VCT 2000A Outline and Dimensions
Pin Descriptions
Pin # Pin Name Pin Description
1 ENABLE/TRI-STATE VCXO Enable (Enable = 0, Disable = 1 = CMOS Outputs Tri-stated)
2, 3, 14,
15 No Connection No Connection
4 REFA 8kHz CMOS Reference Freque ncy Input
5 SELA/B Input Reference Select Pin (REFA = 0, REFB = 1)
6 RESET RESET (RESE T = 1)
7 REFB 8kHz CMOS Reference Freque ncy Input
8, 17 GND Ground
9 FRstatus Free Run Status (FR = 1)
10 Vcc Supply Voltage
11 Optional Reserved for Optional Use
12 ALARM Loss of Reference / Lock alarm (Alarm = 1)
13 FR Force Free Run (Phase Lock = 0, Free Run = 1)
16 /Q LVPECL Complementary Output
18 Q LVPECL Output
Module Data Sheet: VCT2000A 155.520MHz
Application: LVPECL Output-Dual Input Clock Generator
Page 4 of 5 Rev. “7” 6/02/03
Dimensions for Pads
I/O Truth Table
Inputs
Outputs
Reset Enable/
Tri State SEL
A/B REF A REF B Free
Run Free Run
Status Alarm Oscillator
Output 8 kHz Output
1 0 X X X X 1 X X X
X 1 X X X X Tri s tat e Tri State F r ee Run Tri Stat e
0 0 X X X 1 1 1 Free Run Free Run
0 0 0 Ref A
Available Ref B
Available 0 0 0 Ref A Lock Ref A Lock
0 0 1 Not
Available Ref B
Available 0 0 0 Ref B Lock Ref B Lock
0 0 0 Not
Available Ref B
Available 0 0 0 Free Run Free Run
0 0
0 Not
Available Ref B
Available 0 0 1 Free Run Free Run
0 0
1 Ref A
Available Not
Available 0 0 1 Free Run Free Run
0 0
0 Ref A
Available Not
Available 0 0 0 Ref A Lock Ref A Lock
0 0
X Not
Available Not
Available 0 1 1 Free Run Free Run
Module Data Sheet: VCT2000A 155.520MHz
Application: LVPECL Output-Dual Input Clock Generator
Page 5 of 5 Rev. “7” 6/02/03
4.0 STANDARD ENVIRONMENTAL LIMITS
This product is capable of operating within the following environmental conditions:
4.1 Operating Temperature 0 to +70 °C.
4.2 Storage Temperature -40 to +85°C.
4.3 Humidity (non- Condensing) 85% Relative humidity max @ 40°C.
4.4 Atmospheric Pressure 730 to 780 mm Hg.
4.5 Vibration 10 Gs 10 to 500 Hz with double amplitude of
1.52mm max.
4.6 Shock 100G, with pulse width
1mSec.
(1 shock in each of 6 directions of 3
perpendicular planes).
5.0 MAXIMUM SOLDERING PROFILE
Temperature 110 to150 °C >183°C >220°C 220°C
Time 6min 2.0min 0.5min Max temperature
6.0 ALARM
Loss of Lock Alarm
Pin 1 Locator
