DATASHEET
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
Description
Features
The ICS728 combines the functions of a VCXO (Voltage
Controlled Crystal Oscillator) and PLL (Phase Locked
Loop) frequency doubler onto a single chip. Used in
conjunction with an external pullable quartz crystal, this
monolithic integrated circuit replaces more costly hybrid
(canned) VCXO devices. The ICS728 is designed primarily
for data and clock recovery applications within end products
such as set-top box receivers.
• Ideal for set-top box applications using 13.5 MHz external
pullable crystal to generate lock 27 MHz clock transport
video clock
• On-chip VCXO with guaranteed pull range of ±110 ppm
minimum
• VCXO input tuning voltage 0 to 3.3 V
• Packaged in 8-pin SOIC (150 mil wide)
• Available in Pb (lead) free package
The ICS728 exhibits a moderate VCXO gain of 110 ppm/V
typical, when used with a high quality external pullable
quartz crystal.
NOTE: EOL for non-green parts to occur on 5/13/10
per PDN U-09-01
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 3.3
V.
Block Diagram
VIN
13.5 MHz
Pullable
Crystal
X1
X2
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
Voltage
Controlled
Crystal
Oscillator
PLL
Frequency
Doubler
1
27 MHz
(2x Crystal Frequency)
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
Pin Assignment
X1
1
8
X2
VDD
2
7
GN D
VI N
3
6
DC
GN D
4
5
CL K
8 - pi n ( 1 5 0 mi l ) S OI C
Pin Descriptions
Pin
Number
Pin
Name
Pin
Type
1
XI
Input
Crystal connection. Connect to the external pullable crystal.
2
VDD
Power
Connect to +3.3 V (0.01uf decoupling capacitor recommended).
3
VIN
Input
Voltage input to VCXO. Zero to 3.3 V analog input which controls the
oscillation frequency of the VCXO.
4
GND
Power
Connect to ground.
5
CLK
Output
Clock output.
6
DC
__
7
GND
Power
Connect to ground.
8
X2
Input
Crystal connection. Connect to the external pullable crystal.
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
Pin Description
Do not connect to this pin
2
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
External Component Selection
measured with a physical load of 14 pF.
The ICS728 requires a minimum number of external
components for proper operation.
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 ICS728. 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.
Decoupling Capacitor
A decoupling capacitor of 0.01µF must be connected
between VDD (pin 2) and GND (pin 4), as close to these
pins 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.
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 and by PCB layout.
The typical required capacitor value is 1 to 4 pF.
Series Termination Resistor
When the PCB trace between the clock output (CLK, pin 5)
and the load is over 1 inch, series termination should be
used. To series terminate a 50Ω trace (a commonly used
trace impedance) place a 33Ω resistor in series with the
clock line, as close to the clock output pin as possible. The
nominal impedance of the clock output is 20Ω.
To determine the need for and value of the crystal
adjustment capacitors, you will need a PC board of your final
layout, a frequency counter capable of 1 ppm resolution and
accuracy, two power supplies, and some samples of the
crystals which you plan to use in production, along with
measured initial accuracy for each crystal at the specified
crystal load capacitance, CL.
Quartz Crystal
The ICS728 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.
To determine the value of the crystal capacitors:
1. Connect VDD of the ICS728 to 3.3 V. Connect pin 3 of the
ICS728 to the second power supply. Adjust the voltage on
pin 3 to 0V. Measure and record the frequency of the CLK
output.
The frequency of oscillation of a quartz crystal is determined
by its “cut” and by the load capacitors connected to it. The
ICS728 incorporates on-chip variable load capacitors that
“pull” (change) the frequency of the crystal. The crystal
specified for use with the ICS728 is designed to have zero
frequency error when the total of on-chip + stray
capacitance is 14 pF.
Recommended Crystal Parameters:
Initial Accuracy at 25° C
Temperature Stability
Aging
Load Capacitance
Shunt Capacitance, C0
C0/C1 Ratio
Equivalent Series Resistance
2. Adjust the voltage on pin 3 to 3.3 V. Measure and record
the frequency of the same output.
To calculate the centering error:
6 ( f 3.0V – f t arg et ) + ( f 0V – f t arg et )
Error = 10 x ------------------------------------------------------------------------------ – error xtal
f t arg et
Where:
±20 ppm
±30 ppm
±20 ppm
14 pf
7 pF Max
250 Max
35 Ω Max
ftarget = nominal crystal frequency
errorxtal =actual initial accuracy (in ppm) of the crystal being
measured
If the centering error is less than ±25 ppm, no adjustment is
needed. If the centering error is more than 25 ppm negative,
the PC board has excessive stray capacitance and a new
PCB layout should be considered to reduce stray
The third overtone mode of the crystal and all spurs must be
>100 ppm distant from 3x the fundamental resonance
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
3
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
capacitance. (Alternately, the crystal may be re-specified to
a higher load capacitance. Contact IDT for details.) If the
centering error is more than 25 ppm positive, add identical
fixed centering capacitors from each crystal pin to ground.
The value for each of these caps (in pF) is given by:
External Capacitor = 2 x (centering error)/(trim sensitivity)
Trim sensitivity is a parameter which can be supplied by your
crystal vendor. If you do not know the value, assume it is 30
ppm/pF. After any changes, repeat the measurement to
verify that the remaining error is acceptably low (typically
less than ±25 ppm).
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS728. These ratings, which are
standard values for IDT 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.
Item
Rating
Supply Voltage, VDD
7V
All Inputs and Outputs
-0.5 V to VDD+0.5 V
Storage Temperature
-65 to +150° C
Soldering Temperature
260° C
Recommended Operation Conditions
Parameter
Min.
Ambient Operating Temperature
Power Supply Voltage (measured in respect to GND)
Reference crystal parameters
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
Typ.
Max.
Units
0
+70
°C
+3.15
+3.45
V
Refer to page 3
4
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
DC Electrical Characteristics
VDD=3.3 V ±5% , Ambient temperature 0 to +70° C, unless stated otherwise
Parameter
Symbol
Conditions
Operating Voltage
VDD
Output High Voltage
VOH
IOH = -12 mA
Output Low Voltage
VOL
IOL = 12 mA
Output High Voltage (CMOS
Level)
VOH
IOH = -4 mA
Operating Supply Current
IDD
Output = 27 MHz,
no load
Short Circuit Current
IOS
VIN, VCXO Control Voltage
VIA
Min.
Typ.
3.15
Max.
Units
3.45
V
2.4
V
0.4
V
VDD-0.4
V
12
mA
±50
mA
0
3.3
V
AC Electrical Characteristics
VDD = 3.3 V ±5%, Ambient Temperature 0 to +70° C, unless stated otherwise
Parameter
Symbol
Output Frequency
FO
Crystal Pullability
FP
VCXO Gain
Conditions
Min.
Typ.
Max. Units
27
0V< VIN < 3.3 V, Note 1
MHz
+ 110
VIN = VDD/2 +1 V, Note 1
ppm
120
ppm/V
Output Rise Time
tOR
0.8 to 2.0 V, CL=15 pF
1.5
ns
Output Fall Time
tOF
2.0 to 0.8 V, CL=15 pF
1.5
ns
Output Clock Duty Cycle
tD
Measured at 1.4 V, CL=15 pF
60
%
Maximum Output Jitter,
short term
tJ
CL=15 pF
40
50
100
ps
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
Thermal Characteristics
Parameter
Thermal Resistance Junction to
Ambient
Thermal Resistance Junction to Case
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
Symbol
Conditions
Min.
Typ.
Max. Units
θJA
Still air
150
° C/W
θJA
1 m/s air flow
140
° C/W
θJA
3 m/s air flow
120
° C/W
40
° C/W
θJC
5
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
Marking Diagram
8
Marking Diagram (Pb free)
5
8
ICS728M
######
YYWW$$
1
5
728MLF
######
YYWW
4
1
4
Notes:
1. ###### is the lot number.
2. YYWW is the last two digits of the year and week that the part was assembled.
3. “LF” denotes Pb (lead) free package.
4. Bottom marking: (origin)
Origin = country of origin of not USA.
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
6
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
Package Outline and Package Dimensions (8-pin SOIC, 150 Mil. Narrow Body)
Package dimensions are kept current with JEDEC Publication No. 95
8
E
Symbol
Millimeters
Min
Max
Inches
Min
Max
A
A1
B
C
D
E
e
H
h
L
a
1.35
1.75
1.10
0.25
0.33
0.51
0.19
0.25
4.80
5.00
3.80
4.00
1.27 Basic
5.80
6.20
0.25
0.50
0.40
1.27
8°
0°
0.0532 0.0688
0.0040 0.0098
0.013
0.020
0.0075 0.0098
.1890
.1968
0.1497 0.1574
0.050 Basic
0.2284 0.2440
0.010
0.020
0.016
0.050
0°
8°
H
INDEX
AREA
1 2
D
A
h x 45
A1
C
-Ce
B
SEATING
PLANE
L
.10 (.004)
C
Ordering Information
Part / Order Number
728M*
728MT*
728MLF
728MLFT
Marking
Shipping Packaging
Package
see page 6
Tubes
Tape and Reel
Tubes
Tape and Reel
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
Temperature
0 to +70°
0 to +70°
0 to +70°
0 to +70°
C
C
C
C
*NOTE: EOL for non-green parts to occur on 5/13/10 per PDN U-09-01
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 Device Technology (IDT) 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 IDT. IDT reserves the right to change any circuitry or specifications without notice. IDT
does not authorize or warrant any IDT product for use in life support devices or critical medical instruments.
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
7
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
Revision History
Rev.
Originator
Date
A
J. Sarma
12/14/04
Release from Prelim to Final; release as General purpose device.
B
J. Sarma
01/25/05
Add marking diagrams; add LF.
11/04/09
Added EOL note for non-green parts.
C
Description of Change
IDT™ / ICS™ LOW COST 27 MHZ 3.3 VOLT VCXO
8
ICS728
REV C 110409
ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
VCXO
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For Sales
For Tech Support
800-345-7015
408-284-8200
Fax: 408-284-2775
ww.idt.com/go/clockhelp
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Integrated Device Technology, Inc.
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© 2006 Integrated Device Technology, Inc. All rights reserved. Product specifications subject to change without notice. IDT and the IDT logo are trademarks of Integrated Device
Technology, Inc. Accelerated Thinking is a service mark of Integrated Device Technology, Inc. All other brands, product names and marks are or may be trademarks or registered
trademarks used to identify products or services of their respective owners.
Printed in USA