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MK3727E
LOW COST 27 MHZ 3.3 VOLT VCXO
Description
The MK3727E 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 MK3727E is designed primarily for data and clock recovery applications within end products such as set-top box receivers. The MK3727E exhibits a moderate VCXO gain of 120 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 V.
Features
* MK3727E offers 24-36 MHz output frequency range
(output frequency = 2x crystal frequency) and improved power supply noise rejection
* Uses an inexpensive 12 to 18 MHz external crystal * Ideal for set-top box applications using 13.5 MHz
external pullable crystal to generate lock 27 MHz clock transport video clock
* Ideal for ADSL applications using 17.664 MHz
external pullable crystal to generate locked 35.328 MHz clock physical layer clock
* On-chip VCXO with guaranteed pull range of 115
ppm minimum
* * * *
VCXO input tuning voltage 0 to 3.3 V Packaged in 8 pin SOIC (150 mil wide) Available in Pb (lead) free packaging Exact drop-in replacement for MK3727S
Block Diagram
VIN
12-18 MHz Pullable Crystal
X1
X2
Voltage Controlled Crystal Oscillator
PLL Frequency Doubler
24-36 MHz (2x Crystal Frequency)
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Pin Assignment
X1 VDD VIN GND 1 2 3 4 MK3727E 8 Pin (150 mil) SOIC 8 7 6 5 X2 GND NC CLK
Pin Descriptions
Pin Number
1 2 3 4 5 6 7 8
Pin Name
XI VDD VIN GND CLK NC 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 -- 0 to 3.3 V analog input which controls the oscillation frequency of the VCXO. Connect to ground. Clock output. No internal connection (may connect to ground or VDD). Connect to ground. Crystal connection. Connect to the external pullable crystal.
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External Component Selection
The MK3727E requires a minimum number of external components for proper operation.
Shunt Capacitance, C0 C0/C1 Ratio Equivalent Series Resistance
7 pF Max 250 Max 35 Max
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.
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 MK3727E. 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. Crystals can be made to resonate either at the fundamental frequency, or on the third, fifth, or even higher overtone. VCXO crystals are always fundamental mode, because overtone modes are much less pullable and require additional oscillator circuitry for proper operation. The third overtone mode is not necessarily at exactly three times the fundamental frequency. The mechanical properties of the quartz element dictate the position of the overtones relative to the fundamental, and in a VCXO circuit, the third overtone is not typically exactly three times the fundamental, or the oscillator circuit may excite both the fundamental and overtone modes simultaneously. This will cause a nonlinearity in the transfer curve such as the one in Figure 3. This potential problem is why VCXO crystals are required to be tested for absence of any activity inside a +/-100 ppm window at three times the fundamental frequency.
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 MK3727E 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 MK3727E incorporates on-chip variable load capacitors that "pull" (change) the frequency of the crystal. The crystal specified for use with the MK3727E is designed to have zero frequency error when the total of on-chip + stray capacitance is 14pF. Recommended Crystal Parameters: Initial Accuracy at 25C Temperature Stability Aging Load Capacitance
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. The procedure for determining the value of these capacitors can be found in application note MAN05.
20 ppm 30 ppm 20 ppm 14 pf
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Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK3727E. 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 Ambient Operating Temperature Storage Temperature Soldering Temperature 7V
Rating
-0.5 V to VDD+0.5 V 0 to +70C -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 10 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
VCXO Crystal frequency = 1/2 Output 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.
24 + 115
Typ.
Max. Units
36 MHz ppm
120 1.5 1.5 40 50 100 60
ppm/V ns ns % ps
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
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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
Millimeters Min Max Inches Min Max
Symbol
Index Area
EH
Pin 1
D
h x 45 0
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 0 8
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 Q e b c
Ordering Information
Part / Order Number
MK3727E MK3727ETR MK3727ELF MK3727ELFTR
Marking
MK3727E MK3727E MK3727EL MK3727EL
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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