DATASHEET
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
Description
The MK3727D 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 MK3727D is designed
primarily for data and clock recovery applications within end
products such as ADSL modems, set-top box receivers,
and telecom systems.
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.
MK3727D
Features
•
24 to 36 MHz output frequency range (output frequency =
2x crystal frequency)
•
Uses an inexpensive 12 to 18 MHz external crystal
•
Ideal for ADSL applications using 17.664 MHz external
pullable crystal to generate locked 35.328 MHz clock
physical layer clock
•
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 ±115 ppm
minimum
•
VCXO input tuning voltage 0 to 3.3 V
•
Packaged in 8-pin SOIC (150 mil wide)
•
Available in Pb-free packaging
Block Diagram
V IN
12 to 1 8 M H z
P ullab le
C rystal
X1
X2
V o lta g e
C o n tro lled
C ry sta l
O s cilla to r
PLL
F re q u e n c y
D o u b ler
24 to 36 M H z
(2x C rystal F re q ue ncy)
IDT™ / ICS™
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
1
MK3727D
REV M 030806
MK3727D
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
VCXO AND SYNTHESIZER
Pin Assignment
X1
VDD
VIN
GND
1
2
3
4
8
7
6
5
X2
GND
NC
CLK
8-Pin (150 mil)
SOIC
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 (0.01 µf 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.
IDT™ / ICS™
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
2
MK3727D
REV M 030806
MK3727D
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
VCXO AND SYNTHESIZER
External Component Selection
The MK3727D requires a minimum number of external
components for proper operation.
the MK3727D. 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.
Crystal Tuning Load Capacitors
Decoupling Capacitor
A decoupling capacitor of 0.01µF must be connected
between VDD and GND, 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 crystal traces should include pads for small fixed
capacitors, one between X1 and ground, and another
between X2 and ground. 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.
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.
Quartz Crystal
The MK3727D 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
MK3727D incorporates on-chip variable load capacitors that
“pull” (change) the frequency of the crystal. The crystal
specified for use with the MK3727D 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
±20 ppm
±30 ppm
±20 ppm
14 pf
7 pF Max
250 Max
35Ω 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
IDT™ / ICS™
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
3
MK3727D
REV M 030806
MK3727D
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
VCXO AND SYNTHESIZER
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK3727D. 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 +70°C
-65 to +150°C
260°C
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
DC Electrical Characteristics
VDD=3.3 V ±5%
, Ambient temperature 0 to +70°C, 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
V
OH
V
OL
V
OH
IDD
I
OS
V
IA
Conditions
I
OH
= -12 mA
I
OL
= 12 mA
I
OH
= -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
IDT™ / ICS™
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
4
MK3727D
REV M 030806
MK3727D
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
VCXO AND SYNTHESIZER
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
F
O
F
P
t
OR
t
OF
t
D
t
J
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, C
L
=15 pF
2.0 to 0.8 V, C
L
=15 pF
Measured at 1.4 V, C
L
=15 pF
C
L
=15 pF
Min.
24
+ 115
Typ.
Max. Units
36
MHz
ppm
120
1.5
1.5
45
50
100
55
ppm/V
ns
ns
%
ps
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
Thermal Characteristics
Parameter
Thermal Resistance Junction to
Ambient
Symbol
θ
JA
θ
JA
θ
JA
θ
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
IDT™ / ICS™
LOW COST 24 TO 36 MHZ 3.3 VOLT VCXO
5
MK3727D
REV M 030806
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