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ICS728
LOW COST 27 MHZ 3.3 VOLT VCXO
Description
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. The ICS728 exhibits a moderate VCXO gain of 110 ppm/V typical, when used with a high quality external pullable quartz crystal. 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.
Features
* 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
Block Diagram
VIN
13.5 MHz Pullable Crystal
X1
X2
Voltage Controlled Crystal Oscillator
PLL Frequency Doubler
27 MHz (2x Crystal Frequency)
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Pin Assignment
X1 VDD VI N GN D 1 2 3 4 8 7 6 5 X2 GND DC CLK
8 - pi n ( 1 5 0 mi l ) SOI C
Pin Descriptions
Pin Number
1 2 3 4 5 6 7 8
Pin Name
XI VDD VIN GND CLK DC GND X2
Pin Type
Input Power Input Power Output __ Power Input
Pin Description
Crystal connection. Connect to the external pullable crystal. Connect to +3.3 V (0.01uf decoupling capacitor recommended). Voltage input to VCXO. Zero to 3.3 V analog input which controls the oscillation frequency of the VCXO. Connect to ground. Clock output. Do not connect to this pin Connect to ground. Crystal connection. Connect to the external pullable crystal.
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External Component Selection
The ICS728 requires a minimum number of external components for proper operation.
The third overtone mode of the crystal and all spurs must be >100 ppm distant from 3x the fundamental resonance measured with a physical load of 14 pF. 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 0.01F 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. 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. 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. 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: Where:
6 ( f 3.0V - f t arg et ) + ( f 0V - f t arg et ) Error = 10 x ------------------------------------------------------------------------------ - error xtal f t arg et
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 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 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. 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 25C Temperature Stability Aging Load Capacitance Shunt Capacitance, C0 C0/C1 Ratio Equivalent Series Resistance
ftarget = nominal crystal frequency 20 ppm 30 ppm 20 ppm 14 pf 7 pF Max 250 Max 35 Max 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 capacitance. (Alternately, the crystal may be re-specified to a higher load
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capacitance. Contact ICS 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 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.
Item
Supply Voltage, VDD All Inputs and Outputs Storage Temperature Soldering Temperature 7V
Rating
-0.5 V to VDD+0.5 V -65 to +150C 260C
Recommended Operation Conditions
Parameter
Ambient Operating Temperature Power Supply Voltage (measured in respect to GND) Reference crystal parameters
Min.
0 +3.15
Typ.
Max.
+70 +3.45
Units
C V
Refer to page 3
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DC Electrical Characteristics
VDD=3.3 V 5% , Ambient temperature 0 to +70C, unless stated otherwise
Parameter
Operating Voltage Output High Voltage Output Low Voltage Output High Voltage (CMOS Level) Operating Supply Current Short Circuit Current VIN, VCXO Control Voltage
Symbol
VDD VOH VOL VOH IDD IOS VIA
Conditions
IOH = -12 mA IOL = 12 mA IOH = -4 mA Output = 27 MHz, no load
Min.
3.15 2.4
Typ.
Max.
3.45 0.4
Units
V V V V
VDD-0.4 12 50 0 3.3
mA mA V
AC Electrical Characteristics
VDD = 3.3 V 5%, Ambient Temperature 0 to +70 C, unless stated otherwise
Parameter
Output Frequency Crystal Pullability VCXO Gain Output Rise Time Output Fall Time Output Clock Duty Cycle Maximum Output Jitter, short term
Symbol
FO FP tOR tOF tD tJ
Conditions
0V< VIN < 3.3 V, Note 1 VIN = VDD/2 +1 V, Note 1 0.8 to 2.0 V, CL=15 pF 2.0 to 0.8 V, CL=15 pF Measured at 1.4 V, CL=15 pF CL=15 pF
Min.
+ 110
Typ.
27 120
Max. Units
MHz ppm ppm/V 1.5 1.5 ns ns % ps
40
50 100
60
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
Thermal Characteristics
Parameter
Thermal Resistance Junction to Ambient
Symbol
JA JA JA JC
Conditions
Still air 1 m/s air flow 3 m/s air flow
Min.
Typ.
150 140 120 40
Max. Units
C/W C/W C/W C/W
Thermal Resistance Junction to Case
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Marking Diagram
8 5
Marking Diagram (Pb free)
8 5
ICS728M ###### YYWW$$
1 4 1
728MLF ###### YYWW
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.
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Package Outline and Package Dimensions (8-pin SOIC, 150 Mil. Narrow Body)
Package dimensions are kept current with JEDEC Publication No. 95
8
Symbol
E INDEX AREA H
Millimeters Min Max
Inches Min Max
12 D
A A1 B C D E e H h L a
h x 45
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
A A1
C
-Ce
B SEATING PLANE L
.10 (.004)
C
Ordering Information
Part / Order Number
ICS728M ICS728MT ICS728MLF ICS728MLFT
Marking
see page 6
Shipping Packaging
Tubes Tape and Reel Tubes Tape and Reel
Package
8-pin SOIC 8-pin SOIC 8-pin SOIC 8-pin SOIC
Temperature
0 to +70 C 0 to +70 C 0 to +70 C 0 to +70 C
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.
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Revision History
Rev.
A B
Originator
J. Sarma J. Sarma
Date
12/14/04 01/25/05
Description of Change
Release from Prelim to Final; release as General purpose device. Add marking diagrams; add LF.
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