DATASHEET
LOW COST 27 MHZ VCXO
Description
The MK2727 is IDT’s lowest cost, low-jitter,
high-performance VCXO and PLL clock synthesizer
designed to replace expensive 27MHz VCXOs. The on-chip
Voltage Controlled Crystal Oscillator accepts a 0 to 3V input
voltage to cause the output clocks to vary by ±100 ppm.
Using IDT’s patented VCXO and analog Phase-Locked
Loop (PLL) techniques, the device uses an inexpensive
external 13.5 MHz pullable crystal input to produce a 27
MHz output clock.
IDT manufactures the largest variety of Set-Top Box and
multimedia clock synthesizers for all applications. If more
clock outputs are needed, see the MK2731 or MK277x
family of parts. Consult IDT to eliminate VCXOs, crystals
and oscillators from your board.
MK2727
Features
•
•
•
•
•
•
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Packaged in 8-pin narrow SOIC
Uses an inexpensive 13.500 MHz external crystal
On-chip VCXO with pull range of 200 ppm (minimum)
VCXO input tuning voltage 0 to 3.3 V
25 mA output drive capability at TTL levels
Advanced, low-power, sub-micron CMOS process
5 V operating voltage
Block Diagram
VIN
13.5 MHz
Pullable
Crystal
X1
X2
Voltage
Controlled
Crystal
Oscillator
PLL/Clock
Synthesis
Circuitry
27 MHz
IDT™
LOW COST 27 MHZ VCXO
1
MK2727
REV E 051310
MK2727
LOW COST 27 MHZ VCXO
VCXO
External Component Selection
The MK2727 requires a minimum number of external
components for proper operation.
specified for use with the MK2727 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
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.
±20 ppm
±30 ppm
±20 ppm
14 pf
7 pF Max
250 Max
35Ω Max
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
.
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 MK2727. 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
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.
Quartz Crystal
The MK2727 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
MK2727 incorporates on-chip variable load capacitors that
“pull” (change) the frequency of the crystal. The crystal
IDT™
LOW COST 27 MHZ VCXO
3
MK2727
REV E 051310
MK2727
LOW COST 27 MHZ VCXO
VCXO
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK2727. 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
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
+4.75
Typ.
5.0
Max.
+70
+5.25
Units
°
C
V
Refer to page 3
DC Electrical Characteristics
VDD=5 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
= -25 mA
I
OL
= 25 mA
I
OH
= -8 mA
No load
Min.
4.75
2.4
Typ.
Max.
5.25
0.4
Units
V
V
V
V
VDD-0.4
20
±100
0
3
mA
mA
V
IDT™
LOW COST 27 MHZ VCXO
4
MK2727
REV E 051310
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