M908-01 Datasheet Rev 2.1 Revised 30Jul2004
Integrated Circuit Systems, Inc. ● Communications Modules ● www.icst.com ● tel (508) 852-5400
M908-01
VCSO BASED GBE CLOCK GENERATOR
Integrated
Circuit
Systems, Inc.
Product Data Sheet
GENERAL DESCRIPTION
The M908-01 is a PLL (Phase Locked Loop) based
clock generator that uses an
internal VCSO (Voltage Controlled
SAW Oscillator) to produce a very
low jitter output clock. It is ideal for
Gigabit Ethernet. The output clock
(frequency of 156.25 or 187.50MHz
for example) is provided from eight
LVPECL clock output pairs. (Specify frequency at time
of order.) The accuracy of the output frequency is
assured by the internal PLL, which phase-locks the
internal VCSO to the reference input frequency (25 or
30MHz for example). The input reference can either
be an external crystal, utilizing the internal crystal
oscillator, or a stable external clock source such as
a packaged crystal oscillator.
FEATURES
◆Output clock frequency from 125MHz to 190MHz
(Consult factory for frequency availability)
◆Eight identical LVPECL output pairs
◆Integrated SAW (surface acoustic wave) delay line
◆Low jitter 0.7ps RMS (over 12kHz-20MHz)
◆Ideal for Gigabit Ethernet clock reference
◆Output-to-output skew < 100ps
◆External XTAL or LVCMOS reference input
◆Industrial temperature grade available
◆Single 3.3V power supply
◆Small 9 x 9 mm SMT (surface mount) package
PIN ASSIGNMENT (9 x 9 mm SMT)
Figure 1: Pin Assignment
SIMPLIFIED BLOCK DIAGRAM
Figure 2: Simplified Block Diagram
Example Output Frequency Configurations
Ref Clock
Frequency
(MHz)
PLL
Ratio
Output
Frequency 1
(MHz)
Note 1:Specify output clock frequency at time of order
Application
20
25/4
125.00 GbE
25 156.25 10GbE
30 187.50 12GbE
Table 1: Example Output Frequency Configurations
M908-01
(Top View)
XTAL_1 / REF_IN
GND
nFOUT5
FOUT5
nFOUT4
FOUT4
nFOUT3
FOUT3
VCC
nFOUT2
FOUT2
nFOUT1
FOUT1
GND
nFOUT0
FOUT0
VCC
GND
XTAL_2
FOUT6
nFOUT6
FOUT7
nFOUT7
VCC
DNC
DNC
DNC
nOP_IN
OP_OUT
VC
nVC
nOP_OUT
OP_IN
GND
GND
GND
19
20
21
22
23
24
25
26
27
1
2
3
4
5
6
7
8
9
29
30
31
32
33
34
35
36
28
17
16
15
14
13
12
11
10
18
XTAL
OSC
External
Crystal
or
Reference
Clock Input
(e.g., 25 or 30 MHz)
LVPECL
Output
Clock Pairs
(e.g., 156.25
or 187.50MHz)
Divider
VSCO
Frequency
Multiplying
PLL
External Loop Filter
M908-01
FOUT2
nFOUT2
FOUT4
nFOUT4
FOUT3
nFOUT3
FOUT6
nFOUT6
FOUT5
nFOUT5
FOUT7
nFOUT7
FOUT0
nFOUT0
FOUT1
nFOUT1
M908-01 VCSO Based GbE Clock Generator
M908-01 Datasheet Rev 2.1 2 of 6 Revised 30Jul2004
Integrated Circuit Systems, Inc. ● Communications Modules ● www.icst.com ● tel (508) 852-5400
Integrated
Circuit
Systems, Inc.
M908-01
VCSO B
ASED
G
B
E C
LOCK
G
ENERATOR
Product Data Sheet
DETAILED BLOCK DIAGRAM
Figure 3: Detailed Block Diagram
PIN DESCRIPTIONS
Number Name I/O Configuration Description
1, 2, 3, 10, 14, 26 GND Ground Power supply ground connections.
4
9
OP_IN
nOP_IN Input
External loop filter connections. See Figure 5,
External Loop Filter, on pg. 4.
5
8
nOP_OUT
OP_OUT Output
6
7
nVC
VC Input
11, 19, 33 VCC Power Power supply connection, connect to +3.3V.
12
13
FOUT0
nFOUT0
Output No internal terminator Clock output pairs, differential LVPECL output
(156.25 MHz for the M908-01-156.2500)
15
16
FOUT1
nFOUT1
17
18
FOUT2
nFOUT2
20
21
FOUT3
nFOUT3
22
23
FOUT4
nFOUT4
24
25
FOUT5
nFOUT5
29
30
FOUT6
nFOUT6
31
32
FOUT7
nFOUT7
27 XTAL_1 / REF_IN Input External crystal connection. Also accepts
LVCMOS/LVTTL compatible clock source.
28 XTAL_2 Input External crystal connection. Leave unconnected
when driving pin 27 with external clock reference.
34, 35, 36 DNC Do Not Connect.
Table 2: Pin Descriptions
M908-01
XTAL_2
XTAL_1 / REF_IN XTAL
OSC
R Divider
R = 4
Phase
Detector
VCSO
SAW Delay Line
Phase
Shifter
VCSO
CPOST
CPOST
VCnVC
RPOST
nOP_OUTOP_OUT
RPOST
RLOOP
RLOOP
CLOOP
CLOOP
RIN
RIN
OP_IN nOP_IN
Loop Filter
Amplifier
External
Loop Filter
Components
M Divider
M = 25
Phase Locked Loop (PLL)
FOUT2
nFOUT2
FOUT4
nFOUT4
FOUT3
nFOUT3
FOUT6
nFOUT6
FOUT5
nFOUT5
FOUT7
nFOUT7
FOUT0
nFOUT0
FOUT1
nFOUT1
M908-01 Datasheet Rev 2.1 3 of 6 Revised 30Jul2004
Integrated Circuit Systems, Inc. ● Communications Modules ● www.icst.com ● tel (508) 852-5400
M908-01
VCSO B
ASED
G
B
E C
LOCK
G
ENERATOR
Product Data Sheet
Integrated
Circuit
Systems, Inc.
FUNCTIONAL DESCRIPTION
The M908-01 is a PLL (Phase Locked Loop) based
clock generator that generates output clocks
synchronized to an input reference clock.
The M908-01 combines the flexibility of a VCSO
(Voltage Controlled SAW Oscillator) with the stability of
a crystal oscillator.
Input Reference
The input reference can either be an external, discrete
crystal device or a stable external clock source such as
a packaged crystal oscillator:
•If an external crystal is used with the on-chip crystal
oscillator circuit (XTAL OSC), the external crystal
should be a parallel-resonant, fundamental mode
crystal. Apply it to the XTAL_1 / REF_IN and XTAL_2 input
pins. External crystal load capacitors are also
required.
•If an external LVCMOS/LVTTL clock source is used,
apply it to the XTAL_1 / REF_IN input pin.
In either case, the reference clock is supplied to the
phase detector of the PLL. The M908-01 includes a
reference divider that divides the input reference
frequency by a fixed value “R” and provides the result to
the phase detector.
The PLL
The PLL (Phase Locked Loop) includes the phase
detector, the VCSO, a feedback divider (labeled
“M Divider”), and a reference divider (“R Divider”).
The feedback divider divides the VCSO output
frequency by a fixed value “M” to match the reference
frequency provided to the phase detector by the
reference divider.
By controlling the frequency and phase of the VCSO,
the phase detector precisely locks the frequency and
phase of the feedback divider output to that of the
reference divider output. This creates an output
frequency that is a multiple of the reference frequency
(which is output from the VCSO).
The relationship between the VCSO output frequency,
the M Divider, the R Divider and the input reference
frequency is defined as follows:
For the M908-01-156.2500
(see “Ordering Information” on pg. 6):
•VCSO output frequency = 156.25MHz
•Input reference frequency = 25MHz
•M=25
•R= 4
Therefore, for the M908-01-156.2500:
25
156.25MHz = 25MHz 4
The product of the input crystal frequency and
falls within the lock range of the VCSO.
APPLICATION INFORMATION
This section includes information on the optional
external crystal and on the external loop filter.
The subsections on the loop filter provide example
component values and also briefly describe the SAW
PLL simulator tool and additional application
information available at www.icst.com.
External Crystal Specifications
If an external crystal is used with the on-chip crystal
oscillator circuit (XTAL OSC), the external crystal
should have the following general specifications:
The external crystal will be applied to the XTAL_1 / REF_IN
and XTAL_2 input pins. External crystal load capacitors
are also required.
Recommended External Crystal Configuration
Figure 4: Recommended External Crystal Configuration
XTAL= 25 or 30 MHz, Load Capacitance Specification = 18 pF
C1 = 27 pF
C2 = 33 pF
External load capacitors C1 and C2 present a load of 15 pf
to the crystal (they are seen in series by the crystal through
the common ground connection). With the additional of PCB
trace capacitance and M908-01 input capacitance, the total
load to the crystal is about 18 pf.
Fvcso Fxtal M
R
-----
×=
Crystal Specifications
Parameter Min Typ Max Unit
Crystal Type AT-cut quartz
Mode of Oscillation Fundamental
f0Frequency Range 16 40 MHz
ESR Equivalent Series Resistance 50 Ω
Spurious Response (non-harmonic) -40 dBc
CLLoad Capacitance,
parallel load resonant 16 32 pF
P0Drive Level 0.1 1.0 mW
Table 3: Crystal Specifications
----------
×
M
R
-----
XTAL_2
XTAL XTAL OSC
M9xx-0x
XTAL_1 / REF_IN
C1
C2
M908-01
M908-01 Datasheet Rev 2.1 4 of 6 Revised 30Jul2004
Integrated Circuit Systems, Inc. ● Communications Modules ● www.icst.com ● tel (508) 852-5400
Integrated
Circuit
Systems, Inc.
M908-01
VCSO B
ASED
G
B
E C
LOCK
G
ENERATOR
Product Data Sheet
External Loop Filter
To provide stable PLL operation, and thereby a low jitter
output clock, the M908-01 requires the use of an
external loop filter. This is provided via the provided
filter pins (see Figure 5).
Due to the differential signal path design, the
implementation requires two identical complementary
RC filters as shown here.
Figure 5: External Loop Filter
Refer to the M908-01 product web page at
www.icst.com/products/summary/m908-01.htm for
additional product information.
CPOST
CPOST
V
C
nVC
RPOST
nOP_OUTOP_OUT
RPOST
RLOOP
RLOOP
CLOOP
CLOOP
OP_IN nOP_IN
6 7549 8
External Loop Filter Component Values
PLL Band-
width (kHz)
Damping
Factor
R loop
(kΩ)
C loop
(µF)
R post
(kΩ)
C post
(pF)
0.5 3.0 1.5 4.70 20 1500
1.5 1
Note 1: Optimum loop bandwidth when using an external reference
crystal. Will help to attenuate interference on the crystal’s
sinusoidal clock waveform and therefore will minimize device
output clock jitter.
3.3 4.7 1.00 10 1500
2.1 2
Note 2: Alternative loop filter setting when using an external reference
crystal. Smaller C loop lowers loop damping factor with negligi-
ble increase in output jitter.
1.1 4.7 0.10 10 1500
6.4 4.5 20.0 0.10 20 270
10.6 3
Note 3: Optimum loop bandwidth when using an external reference
crystal oscillator. The square wave clock reference does not
require as much jitter attenuation, which allows for a wider loop
bandwidth and improved system noise tolerance.
4.2 33.0 0.033 20 120
Table 4: External Loop Filter Component Values
ABSOLUTE MAXIMUM RATINGS1
Symbol Parameter Rating Unit
VIInput Voltage -0.5 to VCC +0.5 V
VOOutput Voltage -0.5 to VCC +0.5 V
I OOutput Current 21 mA
VCC Power Supply Voltage 4.6 V
TSStorage Temperature -45 to +100 oC
Table 5: Absolute Maximum Ratings
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the
device. These ratings are stress specifications only. Functional operation of product at these conditions
or any conditions beyond those listed in Recommended Conditions of Operation, DC Characteristics, or
AC Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods
may affect product reliability
.
RECOMMENDED CONDITIONS OF OPERATION
Symbol Parameter Min Typ Max Unit
VCC Positive Supply Voltage 3.135 3.3 3.465 V
TAAmbient Operating Temperature
Commercial 0+70 oC
Industrial -40 +85 oC
Table 6: Recommended Conditions of Operation
M908-01 Datasheet Rev 2.1 5 of 6 Revised 30Jul2004
Integrated Circuit Systems, Inc. ● Communications Modules ● www.icst.com ● tel (508) 852-5400
M908-01
VCSO B
ASED
G
B
E C
LOCK
G
ENERATOR
Product Data Sheet
Integrated
Circuit
Systems, Inc.
ELECTRICAL SPECIFICATIONS
DC Characteristics
Unless stated otherwise, V
CC
=
3.3
V +
5
%,T
A
=
0
o
C
to +
70
o
C (commercial)
1
, T
A
=
-40
o
C
to +
85
o
C (industrial)
1
,
Output Frequency=156.25MHz
1
,
LVPECL outputs terminated with
50
Ω
to V
CC
- 2V
Symbol Parameter Min Typ Max Unit
Power Supply VCC Positive Supply Voltage 3.135 3.3 3.465 V
ICC Power Supply Current 375 mA
Reference
Clock
Input
VIH Input High Voltage
XTAL_1 / REF_IN
(XTAL_2 disconnected)
(Vcc / 2 ) +0.5 Vcc +0.3 V
VIL Input Low Voltage -0.3 (Vcc / 2 ) -0.5 V
IIH Input High Current 150 µA
IIL Input Low Current -5.0 µA
Crystal or
Reference
Clock Input
CIN Input Capacitance XTAL_1 / REF_IN 4pF
Differential
Output
VOH Output High Voltage
FOUT, nFOUT (0-7)
Vcc -1.4 Vcc -1.0 V
VOL Output Low Voltage Vcc -2.0 Vcc -1.7 V
VP-PPeak to Peak Output Voltage 0.5 0.85 V
Table 7: DC Characteristics
Note 1: See Ordering Information on pg. 6
AC Characteristics
Unless stated otherwise, V
CC
=
3.3
V +
5
%,T
A
=
0
o
C
to +
70
o
C (commercial)
1
, T
A
=
-40
o
C
to +
85
o
C (industrial)
1
,
Output Frequency=156.25MHz
1
,
LVPECL outputs terminated with
50
Ω
to V
CC
- 2V
Symbol Parameter Min Typ Max Unit Test Conditions
FOUT Output Frequency Range 125 156.25 190 MHz
FIN Nominal Input Frequency, XTAL_1 / REF_IN 25 MHz
APR VCSO Pull-Range +100 +150 ppm
Φn Single Side Band
Phase Noise
@156.25MHz
1kHz Offset -90 dBc/Hz
10kHz Offset -110 dBc/Hz
100kHz Offset -135 dBc/Hz
J(t) Jitter (rms) 0.7 1.0 ps 12kHz to 20MHz
tDC Output Duty Cycle, High Time 45 50 55 %
tROutput Rise Time FOUT, nFOUT (0-7) 350 450 550 ps 20% to 80%
tFOutput Fall Time FOUT, nFOUT (0-7) 350 450 550 ps 20% to 80%
tSOutput Skew Between Any Pair 100 ps
Table 8: AC Characteristics
Note 1: See Ordering Information on pg. 6
M908-01 Datasheet Rev 2.1 6 of 6 Revised 30Jul2004
Integrated Circuit Systems, Inc. ● Communications Modules ● www.icst.com ● tel (508) 852-5400
Integrated
Circuit
Systems, Inc.
While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems (ICS)
assumes no responsibility for either its use or for the infringement of any patents or other rights of third parties, which would
result from its use. No other circuits, patents, or licenses are implied. This product is intended for use in normal commercial
applications. Any other applications such as those requiring extended temperature range, high reliability, or other extraordinary
environmental requirements are not recommended without additional processing by ICS. ICS reserves the right to change any
circuitry or specifications without notice. ICS does not authorize or warrant any ICS product for use in life support devices or
critical medical instruments.
M908-01
VCSO B
ASED
G
B
E C
LOCK
G
ENERATOR
Product Data Sheet
DEVICE PACKAGE - 9 x 9mm CERAMIC LEADLESS CHIP CARRIER
Mechanical Dimensions:
Figure 6: Device Package - 9 x 9mm Ceramic Leadless Chip Carrier
ORDERING INFORMATION
Part Numbering Scheme
Figure 7: Part Numbering Scheme
Consult factory for frequency availability.
Refer to the SAW PLL application notes web page at
www.icst.com/products/appnotes/SawPllAppNotes.htm
for application notes, including recommended PCB
footprint, solder mask, and furnace profile.
Part Number: M908- 01 - xxx.xxxx
Output Frequency (MHz)
“ -” = 0
to +
70
o
C
(commercial)
See Table 8, right. Consult ICS for other frequencies.
I
= - 40
to +
85
o
C
(industrial)
Temperature
Device Number
Example Part Numbers
Output Freq. (MHz) Temperature Order Part Number
125.00 commercial M908-01 - 125.0000
industrial M908-01
I
125.0000
156.25 commercial M908-01 - 156.2500
industrial M908-01
I
156.2500
187.50 commercial M908-01 - 187.5000
industrial M908-01
I
187.5000
Table 9: Example Part Numbers
