MK3712
3.3 V
OLT
S
ET
-T
OP
B
OX
VCXO
Description
The MK3712 series of devices includes the original
MK3712S and the new MK3712D. The MK3712D is a
drop-in replacement for the MK3712S device.
Compared to the earlier device, the MK3712D offers
improved power supply noise rejection.
The MK3712 is a low cost, low jitter, high performance
3.3 Volt VCXO and PLL clock synthesizer designed to
replace expensive VCXOs and crystals used in Set-Top
Box applications. 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
minimum. Using our analog Phase-Locked Loop (PLL)
techniques, the device uses an external, fundamental
mode 27.0 MHz pullable crystal input to produce output
clocks of 11.0592 MHz, 13.5 MHz, and 27 MHz.
ICS manufactures the largest variety of Set-Top Box
and mulitmedia 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.
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
•
MK3712D is a drop-in replacement for the earlier
MK3712S device
•
Packaged in 8 pin SOIC
•
Operating voltage of 3.3 V (±5%)
•
Fixed output clocks of 11.0592 MHz, 13.5 MHz, and
27 MHz
•
Uses a fundamental mode 27 MHz pullable crystal
•
On-chip patented VCXO with pull range of 200ppm
(minimum)
•
VCXO tuning voltage of 0 to 3.3 V
•
12mA output drive capability at TTL levels
•
Advanced, low power, sub-micron CMOS process
MK3712D is Recommended for New Designs
Block Diagram
VDD
V IN
P LL/C lock
S ynthesis
C ircuitry
V oltage
C ontrolled
C rystal
O scillator
11.0592 M H z
27 M H z
P ullable
C rystal
X1
27 M H z
/2
13.5 M H z
X2
G ND
MDS 3712 B
In tegr ated C ir cu it S yst ems
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5 25 Ra ce Str eet, San Jose, C A 95 126
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Revision 091801
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MK3712
3.3 V
OLT
S
ET
-T
OP
B
OX
VCXO
Pin Assignment
X1
VDD
VIN
GND
1
2
3
4
8
7
6
5
X2
27M
11.0592M
13.5M
MK3712S
MK3712D
8 Pin (150 mil) SOIC
Pin Descriptions
Pin
Number
1
2
3
4
5
6
7
8
Pin
Name
XI
VDD
VIN
GND
13.5M
11.0592M
27M
X2
Pin
Type
Input
Power
Input
Power
Output
Output
Output
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. Zero to 3.3 V analog input which controls the
oscillation frequency of the VCXO.
Connect to ground.
13.5 MHz VCXO clock output.
11.0592 MHz clock output.
27 MHz VCXO clock output.
Crystal connection. Connect to the external pullable crystal.
MDS 3712 B
Int egrat ed C ircuit Syste ms
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525 R ace S tr eet, San Jose, CA 95126
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Revision 091801
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MK3712
3.3 V
OLT
S
ET
-T
OP
B
OX
VCXO
External Component Selection
The MK3712 requires a minimum number of external
components for proper operation.
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.
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 MK3712. 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
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.
To determine the need for and value of the crystal
adjustment capacitors, you will need a PC board of
your final layout, a frequency counter capable of about
1 ppm resolution and accuracy, two power supplies,
and some samples of the crystals which you plan to
use in production, along with measured initial accuracy
for each crystal at the specified crystal load
capacitance, CL.
To determine the value of the crystal capacitors:
1. Connect VDD of the MK3712 to 3.3V. Connect pin 3
of the MK3712 to the second power supply. Adjust the
voltage on pin 3 to 0V. Measure and record the
frequency of the CLK output.
2. Adjust the voltage on pin 3 to 3.3V. Measure and
record the frequency of the same output.
To calculate the centering error:
Series Termination Resistor
When the PCB trace 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 MK3712 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 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 MK3712 incorporates on-chip
variable load capacitors that “pull” (change) the
frequency of the crystal. The crystal specified for use
with the MK3712 is designed to have zero frequency
error when the total of on-chip + stray capacitance is
14pF.
Recommended Crystal Parameters:
Initial Accuracy at 25
°
C
Temperature Stability
Aging
Load Capacitance
Shunt Capacitance, C0
C0/C1 Ratio
Equivalent Series Resistance
6
(
f
3.0V
–
f
t arg et
)
+
(
f
0V
–
f
t arg et
)
Error = 10 x ------------------------------------------------------------------------------
–
error
xtal
f
t arg et
Where:
±20 ppm
±30 ppm
±20 ppm
14 pf
7 pF Max
250 Max
35
Ω
Max
f
target
= nominal crystal frequency
error
xtal
=actual initial accuracy (in ppm) of the crystal
being measured
If the centering error is less than ±25 ppm, no
adjustment is needed. If the centering error is more
than 25ppm negative, the PC board has excessive
stray capacitance and a new PCB layout should be
MDS 3712 B
Int egrat ed C ircuit Syste ms
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MK3712
3.3 V
OLT
S
ET
-T
OP
B
OX
VCXO
considered to reduce stray capacitance. (Alternately,
the crystal may be re-specified to a higher load
capacitance. Contact ICS MicroClock for details.) If the
centering error is more than 25ppm positive, add
identical fixed centering capacitors from each crystal
pin to ground. The value for each of these caps (in pF)
is given by:
External Capacitor =
2 x (centering error)/(trim sensitivity)
Trim sensitivity is a parameter which can be supplied
by your crystal vendor. If you do not know the value,
assume it is 30 ppm/pF. After any changes, repeat the
measurement to verify that the remaining error is
acceptably low (typically less than ±25ppm).
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK3712. 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
-0.5V to VDD+0.5V
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
MDS 3712 B
Int egrat ed C ircuit Syste ms
q
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525 R ace S tr eet, San Jose, CA 95126
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Revision 091801
t el (40 8) 295 -9800
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w ww. ic s t .c o m
MK3712
3.3 V
OLT
S
ET
-T
OP
B
OX
VCXO
DC Electrical Characteristics
VDD=3.3V ±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
No load
Min.
3.15
2.4
Typ.
Max.
3.45
0.4
Units
V
V
V
V
VDD-0.4
11
±50
0
3.3
mA
mA
V
AC Electrical Characteristics
VDD = 3.3V ±5%
, Ambient Temperature 0 to +70° C, unless stated otherwise
Parameter
Crystal Pullability
MK3712D
MK3712S
VCXO Gain
MK3712D
MK3712S
Output Rise Time
Output Fall Time
Output Clock Duty Cycle
Maximum Output Jitter,
short term
t
OR
t
OF
t
D
t
J
VIN = VDD/2 + 1V, Note 1
VIN = VDD/2 + 1V, Note 1
0.8 to 2.0V, C
L
=15pF
2.0 to 0.8V, C
L
=15pF
Measured at 1.4V, C
L
=15pF
C
L
=15pF
40
50
400
120
140
1.5
1.5
60
ppm/V
ppm/V
ns
ns
%
ps
F
P
F
P
0V< VIN < 3.3V, Note 1
0V< VIN < 3.3V, Note 1
+ 115
+ 100
ppm
ppm
Symbol
Conditions
Min.
Typ.
Max. Units
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
MDS 3712 B
Int egrat ed C ircuit Syste ms
q
5
525 R ace S tr eet, San Jose, CA 95126
q
Revision 091801
t el (40 8) 295 -9800
q
w ww. ic s t .c o m
Microchip MCU
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