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MK3720
27 MHZ AND 54 MHZ 3.3 VOLT VCXO
Description
The MK3720D is a drop-in replacement for the MK3720S and MK3720A devices. Compared to these earlier devices the MK3720D offers a wider operating frequency range and improved power supply noise rejection. The MK3720 is a low-cost, low-jitter, high-performance 3.3 Volt VCXO designed to replace expensive 13.5, 27, or 54 MHz VCXOs. The patented on-chip Voltage Controlled Crystal Oscillator accepts a 0 to 3.3 V input voltage to cause the output clocks to vary by 100 ppm. Using ICS' patented VCXO and analog/digital Phase-Locked Loop (PLL) techniques, the device uses an inexpensive external pullable crystal input to produce output clocks of 13.5 MHz, 27 MHz, and 54 MHz. The MK3720D 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.
Features
* MK3720D is a drop-in upgrade to the earlier
MK3720S and MK3720A devices
* * * * * *
Packaged in 8-pin SOIC Available in Pb (lead) free package Operating voltage of 3.3 V (5%) Output clocks of 54, 27, and 13.5 MHz Uses an inexpensive 13.500 MHz external crystal On-chip VCXO (patented) with pull range of 200 ppm (minimum)
* VCXO tuning voltage of 0 to 3.3 V * 12 mA output drive capability at TTL levels * Advanced, low-power, sub-micron CMOS process
MK3720D is Recommended for New Designs
Block Diagram
VDD
V IN 54 M H z 1 3 .5 M H z P u lla b le C ry s ta l X1
V o lta g e C o n tro lle d C ry sta l O s cilla to r P L L /C lo c k S y n th e s is C irc u itry
27 M Hz 1 3 .5 M H z
X2
GND
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MK3720 27 MHZ AND 54 MHZ 3.3 VOLT VCXO
Pin Assignment
X1 V DD VI N GND 1 2 3 4 8 7 6 5 X2 27M 13.5M 54M
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 54M 13.5 27 X2
Pin Type
Input Power Input Power
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.
Output 54 MHz VCXO clock output. Output 13.5 MHz VCXO clock output. Output 27 MHz VCXO clock output. Input Crystal connection. Connect to the external pullable crystal.
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External Component Selection
The MK3720 requires a minimum number of external components for proper operation.
should be no signal traces underneath or close to the crystal.
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.
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.
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 MK3720 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 MK3720 incorporates on-chip variable load capacitors that "pull" (change) the frequency of the crystal. The crystal specified for use with the MK3720 is designed to have zero frequency error when the total of on-chip + stray capacitance is 14 pF. Recommended Crystal Parameters: See application note MAN05 for crystal information. MAN05 is available on the internet at www.icst.com/pdf/man05.pdf. 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 MK3720. There should be no via's between the crystal pins and the X1 and X2 device pins. There
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Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK3720. 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
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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MK3720 27 MHZ AND 54 MHZ 3.3 VOLT VCXO
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 No load
Min.
3.15 2.4
Typ.
Max.
3.45 0.4
Units
V V V V
VDD-0.4 13 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
Crystal Pullability VCXO Gain Output Rise Time Output Fall Time Output Clock Duty Cycle Maximum Output Jitter, short term
Symbol
FP tOR tOF tD tJ
Conditions
0V< VIN < 3.3V, 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, 13.5M CLK CL=15 pF, 27M and 54M CLK
Min.
+ 115
Typ.
120
Max. Units
ppm ppm/V 1.5 1.5 ns ns % ps ps
45
50 80 150
55
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3. Note 2: Original MK3720S and MK3720A provided +100 ppm crystal pullability. Note 3: Original MK3720S and MK3720A provided 100 and 170 ppm/V respectively.
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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 (Note 1)
MK3720D MK3720DTR MK3720DLF MK3720DLFTR
Marking
MK3720D MK3720D MK3720DL MK3720DL
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
Note 1: MK3720D is recommended for new designs. Call factory for information on MK3720A and MK3720S. 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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