DATASHEET
LOW COST VCXO
Description
The MK2731-01 is a low cost, low jitter, high-performance
VCXO and PLL clock synthesizer designed to replace
expensive discrete VCXOs, PLLs and oscillators. 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 ICS’s patented VCXO and analog
Phase-Locked Loop (PLL) techniques, the device uses an
inexpensive 10 MHz or 13.5 MHz pullable crystal input to
produce two low skew output clocks.
ICS manufactures a large variety of Set-Top Box and
multimedia clock synthesizers for all applications. If more
clock outputs are needed, see the MK277x family of parts.
Consult ICS to eliminate VCXOs, crystals and oscillators
from your board.
MK2731-01
Features
•
Packaged in 16-pin narrow SOIC
•
Uses an inexpensive 10 or 13.5 MHz crystal
•
On-chip VCXO (patented) with pull range of 200 ppm
(minimum)
•
•
•
•
VCXO tuning voltage of 0 to 3 V
Zero ppm synthesis error in all clocks
Low skew output clocks - 1 ns maximum
CMOS level outputs with 25 mA output drive capability at
TTL levels
•
Advanced, low power, sub-micron CMOS process
•
5 V operating voltage
Block Diagram
S2:0
VIN
X1
3
CLK1
PLL/Clock
Synthesis
Circuitry
CLK2
10 MHz or 13.5
MHz Pullable
Crystal
X2
Voltage
Controlled
Crystal
Oscillator
OE (both outputs)
IDT™ / ICS™
LOW COST VCXO
1
MK2731-01
REV E 021804
MK2731-01
LOW COST VCXO
VCXO
Pin Assignment
X2
X1
VDD
VIN
GND
GND
OE
CLK1
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VDD
NC
S2
VDD
GND
CLK2
S1
S0
Output Clock Select Table
Input S2
10
10
13.5
13.5
13.5
13.5
—
13.5
0
0
0
0
1
1
1
1
S1
0
0
1
1
0
0
1
1
S0
0
1
0
1
0
1
0
1
CLK1
40
40
40
27
33.33
24.576
32
CLK2
80
OFF
OFF
54
66.66
49.152
64
Test use
16-pin narrow (150 mil) SOIC
(All OFF outputs are stopped low)
Pin Descriptions
Pin
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Pin
Name
X2
X1
VDD
VIN
GND
GND
OE
CLK1
S0
S1
CLK2
GND
VDD
S2
NC
VDD
Pin
Type
Output
Input
Power
Input
Power
Power
Input
Output
Input
Input
Output
Power
Power
Input
--
Power
Pin Description
Crystal connection. Connect to a 10 or 13.5 MHz pullable crystal.
Crystal connection. Connect to a 10 or 13.5 MHz pullable crystal.
Connect to +5 V.
Voltage input to VCXO. Zero to 3 V signal which controls the
VCXO frequency.
Connect to ground.
Connect to ground.
Output Enable. Active high. Tri-states both outputs when low.
Clock output 1 determined by status of S2, S1, and S0. See table
above.
Fixed Clock Select 0. Selects outputs per table above.
Fixed Clock Select 1. Selects outputs per table above.
Clock output 2 determined by status of S2, S1, and S0. See table
above.
Connect to ground.
Connect to +5 V.
Fixed Clock Select 2. Selects outputs per table above.
No connect.
Connect to +5 V.
IDT™ / ICS™
LOW COST VCXO
2
MK2731-01
REV E 021804
MK2731-01
LOW COST VCXO
VCXO
External Component Selection
The MK2731-01 requires a minimum number of external
components for proper operation.
Decoupling Capacitors
Decoupling capacitors of 0.01µF should be connected
between VDD and GND, as close to the MK2731-01 as
possible. For optimum device performance, the decoupling
capacitors should be mounted on the component side of the
PCB. Avoid the use of vias in the decoupling circuit.
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.
Series Termination Resistor
When the PCB traces between the clock outputs and the
loads are 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 MK2731-01 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 meeting ICS’ recommended
parameters must be used, and the layout guidelines
discussed in the following section must be followed.
See Application Note MAN05 for a full list of crystal
parameters.
The frequency of oscillation of a quartz crystal is determined
by its “cut” and by the load capacitors connected to it. The
MK2731-01 incorporates on-chip variable load capacitors
that “pull” (change) the frequency of the crystal. The crystal
specified for use with the MK2731-01 is designed to have
zero frequency error when the total of on-chip + stray
capacitance is 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 MK2731-01. There should be no via’s 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
IDT™ / ICS™
LOW COST VCXO
3
MK2731-01
REV E 021804
MK2731-01
LOW COST VCXO
VCXO
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK2731-01. 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
+4.75
Typ.
Max.
+70
+5.25
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)
Input High Voltage (X1 only)
Input High Voltage
Input Low Voltage (X1 only)
Input Low Voltage
Operating Supply Current
Short Circuit Current
VIN, VCXO Control Voltage
Frequency Synthesis Error
Input Capacitance
Symbol
VDD
V
OH
V
OL
V
OH
V
IH
V
IH
V
IL
V
IL
IDD
I
OS
V
IA
Conditions
I
OH
= -25 mA
I
OL
= 25 mA
I
OH
= -8 mA
Min.
4.75
2.4
Typ.
Max.
5.25
0.4
Units
V
V
V
V
VDD-0.4
3.5
2.0
2.5
1.5
0.8
2.5
V
V
V
V
mA
mA
3
0
V
ppm
pF
No load, S2:0 =
000
Each output
0
All clocks
S0, S1, S2, OE
20
±100
C
IN
7
IDT™ / ICS™
LOW COST VCXO
4
MK2731-01
REV E 021804
MK2731-01
LOW COST VCXO
VCXO
AC Electrical Characteristics
VDD = 3.3 V ±5%,
Ambient Temperature 0 to +70° C, unless stated otherwise
Parameter
CLK1 and CLK2 Output
Pullability
Input Crystal Frequency
Input Crystal Accuracy
Output Clock Rise Time
Output Clock Fall Time
Output Clock Duty Cycle
Maximum Absolute Jitter,
short term
Skew of CLK1 (with respect
to CLK2)
Symbol
f
P
Conditions
0V< VIN < 3 V, Note 1
Min.
+100
Typ.
Max. Units
ppm
10 or
13.5
+30
t
OR
t
OF
t
D
t
J
0.8 to 2.0V
2.0 to 0.8V
Measured at 1.4V
C
L
=15pF
Measured at 1.4V
40
50
200
1
1.5
1.5
60
MHz
ppm
ns
ns
%
ps
ns
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.
120
115
105
58
Max. Units
°C/W
°C/W
°C/W
°C/W
Thermal Resistance Junction to Case
IDT™ / ICS™
LOW COST VCXO
5
MK2731-01
REV E 021804
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
