MDS 3726-12 B
1
Revision 120505
I n t e gra t e d C i r c u i t S y s t e m s
5 2 5 R a c e S t r e e t , S a n J o s e, C A 9 5 1 2 6
t e l ( 4 0 8 ) 2 9 7 - 1 2 0 1
w w w. i c s t . c o m
H
IGH
P
ERFORMANCE
VCXO
ICS3726-12
PRELIMINARY INFORMATION
Description
The ICS3726-12 is a low cost, low-jitter,
high-performance 3.3 volt VCXO designed to replace
expensive discrete VCXOs modules. The ICS3726-12
offers a wider operating frequency range and improved
power supply noise rejection. The on-chip Voltage
Controlled Crystal Oscillator accepts a 0 to 3.3 V input
voltage. Using ICS' patented VCXO techniques, the
device uses an inexpensive external pullable crystal in
the range of 20 to 52 MHz to produce a VCXO output
clock at that same frequency.
This part is ideal for Set-Top Box, multimedia clock
synthesizers and ADSL/VDSL applications.
The frequency of the on-chip VCXO is adjusted by an
external control voltage input into pin VIN. Because
VIN is a high-impedance input, it can be driven directly
from an PWM RC integrator circuit. Frequency output
increases with VIN voltage input. The usable range of
VIN is 0 to VDD.
Features
Packaged in 8-pin SOIC
Operational frequency range of 20 MHz to 52 MHz
Uses an inexpensive external crystal
On-chip patented VCXO with pull range of 400 ppm
VCXO tuning voltage of 0 to VDD
Operating voltage of 3.3 V
12 mA output drive capability at TTL levels
Works with surface mount crystal with CL=10 pF
Advanced, low-power, sub-micron CMOS process
Available in Pb (lead) free package
Block Diagram
X1
X2
Voltage
Controlled
Crystal
Oscillator
VIN
20 to 52 MHz
Pullable Crystal
20 to 52 MHz
Clock (REFOUT)
GND
VDD
Optional tuning
crystal capacitors
H
IGH
P
ERFORMANCE
VCXO
MDS 3726-12 B
2
Revision 120505
I n t e gr a t e d C i r c u i t S y s t e m s
5 2 5 R a c e S t r e e t , S a n J o s e, C A 9 5 1 2 6
t e l ( 4 0 8 ) 2 9 7 - 1 2 0 1
w w w. i c s t . c o m
ICS3726-12
PRELIMINARY INFORMATION
Pin Assignment
Pin Descriptions
X 2
N C
V I N
N C
G N D
R E F O U T
X 1
1
2
3
4
8
7
6
5
I CS 3 7 2 6 - 1 2
8 - P i n ( 1 5 0 mi l ) S OI C
V D D
Pin
Number
Pin
Name
Pin
Type
Pin Description
1
X1
Input
Crystal connection. Connect to the external pullable crystal.
2
NC
--
Do connet to this pin.
3
VIN
Input
Voltage input to VCXO. Zero to VDD signal which controls the
VCXO frequency.
4
GND
Power
Connect to ground.
5
REFOUT
Output
VCXO CMOS level clock output matches the nominal frequency of
the crystal.
6
VDD
Power
Connect to +3.3 V (0.01
f decoupling capacitor recommended).
7
NC
--
No connect. Do not connect this pin to anything.
8
X2
Input
Crystal connection. Connect to a pullable 20 to 52 MHz crystal.
H
IGH
P
ERFORMANCE
VCXO
MDS 3726-12 B
3
Revision 120505
I n t e gr a t e d C i r c u i t S y s t e m s
5 2 5 R a c e S t r e e t , S a n J o s e, C A 9 5 1 2 6
t e l ( 4 0 8 ) 2 9 7 - 1 2 0 1
w w w. i c s t . c o m
ICS3726-12
PRELIMINARY INFORMATION
External Component Selection
The ICS3726-12 requires a minimum number of
external components for proper operation.
Decoupling Capacitors
A decoupling capacitor of 0.01
F should be connected
between VDD and GND on pins 6 and 4 as close to the
ICS3726-12 as possible. For optimum device
performance, the decoupling capacitor should be
mounted on the component side of the PCB. Avoid the
use of vias in the decoupling circuit.
Series Termination Resistor
When the PCB trace between the clock output and the
load is over 1 inch, series termination should be used.
To series terminate a 50
trace (a commonly used
trace impedance), place a 33
resistor in series with
the clock line, as close to the clock output pin as
possible. The nominal impedance of the clock output is
20
.
Quartz Crystal
The ICS3726-12 VCXO function consists of the
external crystal and the integrated VCXO oscillator
circuit. To assure the best system performance
(frequency pull range) and reliability, a crystal device
with the recommended parameters (shown below)
must be used, and the layout guidelines discussed in
the following section shown must be followed.
The oscillation frequency of a quartz crystal is
determined by its "cut" and by the load capacitors
connected to it. The ICS3726-12 incorporates on-chip
variable load capacitors that pull (change) the
frequency of the crystal. The crystal specified for use
with the ICS3726-12 is designed to have zero
frequency error when the total of on-chip + stray
capacitance is 10 pF.
Recommended Crystal Parameters:
Initial Accuracy at 25
C
20 ppm
Temperature Stability
30 ppm
Aging
20 ppm
Load Capacitance
10 pF
Shunt Capacitance, C0
7 pF max
C0/C1 Ratio
250 max
Equivalent Series Resistance
35
max
The external crystal must be connected as close to the
chip as possible and should be on the same side of the
PCB as the ICS3726-12. There should be no vias
between the crystal pins and the X1 and X2 device
pins. There should be no signal traces underneath or
close to the crystal. See application note MAN05.
Crystal Tuning Load Capacitors
The crystal traces should include pads for small fixed
capacitors, one between X1 and ground, and another
between X2 and ground. Stuffing of these capacitors
on the PCB is optional. The need for these capacitors is
determined at system prototype evaluation, and is
influenced by the particular crystal used (manufacture
and frequency) and by PCB layout. The typical required
capacitor value is 1 to 4 pF. This chip has internal load
capacitors and is designed to work with surface mount
crystals with 10 pF load capacitance.
The procedure for determining the value of these
capacitors can be found in application note MAN05.
H
IGH
P
ERFORMANCE
VCXO
MDS 3726-12 B
4
Revision 120505
I n t e gr a t e d C i r c u i t S y s t e m s
5 2 5 R a c e S t r e e t , S a n J o s e, C A 9 5 1 2 6
t e l ( 4 0 8 ) 2 9 7 - 1 2 0 1
w w w. i c s t . c o m
ICS3726-12
PRELIMINARY INFORMATION
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS3726-12. These ratings,
which are standard values for ICS commercially rated parts, are stress ratings only. Functional operation of
the device at these or any other conditions above those indicated in the operational sections of the
specifications is not implied. Exposure to absolute maximum rating conditions for extended periods can
affect product reliability. Electrical parameters are guaranteed only over the recommended operating
temperature range.
Recommended Operation Conditions
Item
Rating
Supply Voltage, VDD
7 V
All Inputs and Outputs
-0.5 V to VDD+0.5 V
Ambient Operating Temperature
0 to +70
C
Storage Temperature
-65 to +150
C
Soldering Temperature
260
C
Parameter
Min.
Typ.
Max.
Units
Ambient Operating Temperature
0
+70
C
Power Supply Voltage (measured in respect to GND)
+3.15
+3.45
V
Reference crystal parameters
Refer to page 3
H
IGH
P
ERFORMANCE
VCXO
MDS 3726-12 B
5
Revision 120505
I n t e gr a t e d C i r c u i t S y s t e m s
5 2 5 R a c e S t r e e t , S a n J o s e, C A 9 5 1 2 6
t e l ( 4 0 8 ) 2 9 7 - 1 2 0 1
w w w. i c s t . c o m
ICS3726-12
PRELIMINARY INFORMATION
DC Electrical Characteristics
VDD=3.3 V 5%
, Ambient temperature 0 to +70
C, unless stated otherwise
AC Electrical Characteristics
VDD = 3.3 V 5%, Ambient Temperature 0 to +70
C, unless stated otherwise
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Operating Voltage
VDD
3.15
3.45
V
Output High Voltage
V
OH
I
OH
= -12 mA
2.4
V
Output Low Voltage
V
OL
I
OL
= 12 mA
0.4
V
Output High Voltage (CMOS
Level)
V
OH
I
OH
= -4 mA
VDD-0.4
V
Operating Supply Current
IDD
No load
6
mA
Short Circuit Current
I
OS
50
mA
VIN, VCXO Control Voltage
V
IA
0
3.3
V
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Output Frequency
F
O
20
52
MHz
Crystal Pullability
F
P
0V< VIN < 3.3 V, Note 1
+ 200
ppm
VCXO Gain
VIN = VDD/2 + 1 V, Note 1
150
ppm/V
Output Rise Time
t
OR
0.8 to 2.0 V, C
L
=15 pF
1.5
ns
Output Fall Time
t
OF
2.0 to 0.8 V, C
L
=15 pF
1.5
ns
Output Clock Duty Cycle
t
D
Measured at 1.4 V, C
L
=15 pF
40
50
60
%
Period Jitter RMS
t
J
C
L
=15 pF @35.328 MHz
6.7
ps
Period Jitter P- P
t
J
C
L
=15 pF@35.328 MHz
46
ps
Integrated Jitter RMS
Integrated 12 kHz to 20 MHz
@ 35.328 MHz
1
ps
Phase Noise relative to
Carrier
@35.328 MHz Carrier
frequency
@10 Hz
-65
dBc/Hz
@100 Hz
-90
dBc/Hz
@1 kHz
-120
dBc/Hz
@10 kHz
-140
dBc/Hz
@100 kHz
-147
dBc/Hz
@1 MHz
-147
dBc/Hz
H
IGH
P
ERFORMANCE
VCXO
MDS 3726-12 B
6
Revision 120505
I n t e gr a t e d C i r c u i t S y s t e m s
5 2 5 R a c e S t r e e t , S a n J o s e, C A 9 5 1 2 6
t e l ( 4 0 8 ) 2 9 7 - 1 2 0 1
w w w. i c s t . c o m
ICS3726-12
PRELIMINARY INFORMATION
Package Outline and Package Dimensions (8-pin SOIC)
Package dimensions are kept current with JEDEC Publication No. 95
Ordering Information
Parts that are ordered with a "LF" suffix to the part number are the Pb-Free configuration and are RoHS compliant.
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.
Part / Order Number
Marking
Shipping Packaging
Package
Temperature
ICS3726M-12
3726M-12
Tubes
8-pin SOIC
0 to +70
C
ICS3726M-12T
3726M-12
Tape and Reel
8-pin SOIC
0 to +70
C
ICS3726M-12LF
3726M12L
Tubes
8-pin SOIC
0 to +70
C
ICS3726M-12LFT
3726M12L
Tape and Reel
8-pin SOIC
0 to +70
C
INDEX
AREA
1 2
8
D
E
SEATING
PLANE
A1
A
e
- C -
B
.10 (.004)
C
C
L
H
h x 45
*For reference only. Controlling dimensions in mm.
Millimeters
Inches*
Symbol
Min
Max
Min
Max
A
1.35
1.75
.0532
.0688
A1
0.10
0.25
.0040
.0098
B
0.33
0.51
.013
.020
C
0.19
0.25
.0075
.0098
D
4.80
5.00
.1890
.1968
E
3.80
4.00
.1497
.1574
e
1.27 BASIC
0.050 BASIC
H
5.80
6.20
.2284
.2440
h
0.25
0.50
.010
.020
L
0.40
1.27
.016
.050
0
8
0
8
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