DATASHEET
USB-DVR CLOCK SOURCE
Description
The MK2746-01 is a low cost, low jitter, high performance
clock synthesizer for USB-DVR based applications. Using
analog Phase Locked Loop (PLL) techniques, the device
accepts a 27 MHz fundamental mode crystal or clock input
to produce multiple output clocks for USB and Video
applications.
IDT manufacturers the largest variety of DVD, set top box,
and multimedia clock synthesizers for all applications.
MK2746-01
Features
•
Packaged in 16 pin TSSOP
•
Operating voltage of 3.3 V
•
Provides three fixed outputs of 27 MHz, 24.576 MHz
(Video), and 24 MHz (USB).
•
Advanced, low power, sub-micron CMOS process
•
RoHS 5 (green) or RoHS 6 (green and lead free)
compliant package
Block Diagram
VDD
4
24.576M Video decoder clock..
PLL / Clock
Circuit
24M USB Clock
27 MHz crystal
or clock
X1/ICLK
X2
Clock Buffer/
Crystal
Ocsillator
3
27M Video Clock
4
G ND
External crystal capacitors may be required
OE
IDT™
USB-DVR CLOCK SOURCE
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MK2746-01
REV E 051310
MK2746-01
USB-DVR CLOCK SOURCE
CLOCK SYNTHESIZER
Pin Assignment
X2
X1/ICLK
VDD
GND
24M
VDD
OE
24.576M
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
27M
27M
27M
VDD
GND
GND
VDD
GND
16 pin (173 mil) TSSOP
Pin Descriptions
Pin
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Pin
Name
X2
X1/ICLK
VDD
GND
24M
VDD
OE
24.576M
GND
VDD
GND
GND
VDD
27M
27M
27M
Pin
Type
Input
Input
Power
Power
Output
Power
Input
Output
Power
Power
Power
Power
Power
Output
Output
Output
Pin Description
Connect to a 27 MHz fundamental mode crystal. Leave open for clock input.
Connect to a 27 MHz fundamental mode crystal or clock.
Connect to +3.3 V.
Connect to ground.
24MHz USB clock output . Internal pull-down to low when OE is low.
Connect to +3.3 V.
Output enable (OE high enables outputs). Internal pull-up.
24.576 MHz clock output. Internal pull-down to low when OE is low.
Connect to ground.
Connect to +3.3 V.
Connect to ground.
Connect to ground.
Connect to +3.3 V.
27 MHz clock output. Internal pull-down to low when OE is low.
27 MHz clock output. Internal pull-down to low when OE is low.
27 MHz clock output. Internal pull-down to low when OE is low.
External Component Selection
The MK2746-01 requires a minimum number of external
components for proper operation.
capacitors should be mounted on the component side of the
PCB. Avoid the use of vias in the decoupling circuit.
Decoupling Capacitors
Decoupling capacitors of 0.01µF should be connected
between VDD and GND as close to the MK2746-01 as
possible. For optimum device performance, the decoupling
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
IDT™
USB-DVR CLOCK SOURCE
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MK2746-01
REV E 051310
MK2746-01
USB-DVR CLOCK SOURCE
CLOCK SYNTHESIZER
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
.
be kept as short as possible, as should the PCB trace to the
ground via. Distance of the ferrite bead and bulk decoupling
from the device is less critical.
2) The external crystal should be mounted just next to the
device with short traces. The X1 and X2 traces should not
be routed next to each other with minimum spaces, instead
they should be separated and away from other traces.
3) To minimize EMI the 33Ω series termination resistor, if
needed, should be placed close to the clock output.
4) An optimum layout is one with all components on the
same side of the board, minimizing vias through other signal
layers (the ferrite bead and bulk decoupling capacitor can be
mounted on the back). Other signal traces should be routed
away from the MK2746-01-01. This includes signal traces
just underneath the device, or on layers adjacent to the
ground plane layer used by the device.
Crystal Tuning Load Capacitors
For a crystal input, a parallel resonant fundamental mode
crystal should be used. Crystal capacitors must be
connected between each of the pins X1 and X2 to ground.
The value (in pF) of these crystal caps should equal
(CL-6)*2. In this equation CL is equal to the crystal load
capacitance in pF. As an example, for a crystal with an 18pF
load capacitance, each crystal capacitor would be 24pF
[(18-6)*2]=24.
PCB Layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
1) The 0.01µF decoupling capacitor should be mounted on
the component side of the board as close to the VDD pin as
possible. No vias should be used between decoupling
capacitor and VDD pin. The PCB trace to VDD pin should
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK2746-01. 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
-0.5V 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)
Min.
0
+3.0
Typ.
Max.
+70
+3.6
Units
°
C
V
IDT™
USB-DVR CLOCK SOURCE
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MK2746-01
REV E 051310
MK2746-01
USB-DVR CLOCK SOURCE
CLOCK SYNTHESIZER
DC Electrical Characteristics
VDD=3.3V ±10%
, Ambient temperature 0 to +70° C, unless stated otherwise
Parameter
Operating Voltage
Input High Voltage
Input Low Voltage
Input High Voltage
Input Low Voltage
Output High Voltage
Output Low Voltage
Output High Voltage (CMOS
Level)
Operating Supply Current
Short Circuit Current
Input Capacitance
Nominal Output Impedance
On Chip Pull Up Resistor
On Chip Pull Down Resistor
Symbol
VDD
V
IH
V
IL
V
IH
V
IL
V
OH
V
OL
V
OH
IDD
I
OS
C
IN
Z
OUT
R
PU
R
PD
Conditions
Min.
3.0
2.0
Typ.
Max.
3.6
0.8
Units
V
V
V
V
V
V
V
V
ICLK
ICLK
I
OH
= -20 mA
I
OL
= 20 mA
I
OH
= -4 mA
No load, OE=1
No load, OE=0
(VDD/2)-1
2.4
VDD/2
VDD/2
(VDD/2)+1
0.4
VDD-0.4
21
15
±50
5
20
510
240
mA
mA
mA
pF
Ω
kΩ
kΩ
AC Electrical Characteristics
VDD = 3.3V ±10%
, Ambient Temperature 0 to +70° C, unless stated otherwise
Parameter
Input Frequency
Output Rise Time
Output Fall Time
Output Clock Duty Cycle
Maximum Output Jitter,
short term
t
OR
t
OF
t
D
t
J
20% to 80% of VDD, Note 1
80% to 20% of VDD, Note 1
at VDD/2, Note 1
All clocks, except REF clocks
Note 1
REF clocks, Note 1
Output Enable time
Output Disable time
Note 1: Measured with 15pF load.
OE high to valid output (PLL
running)
OE low to output disable
45
Symbol
Conditions
Min.
Typ.
27
1.2
1.2
50
+75
+150
Max. Units
MHz
1.8
1.8
55
ns
ns
%
ps
ps
20
20
ns
ns
IDT™
USB-DVR CLOCK SOURCE
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MK2746-01
REV E 051310
MK2746-01
USB-DVR CLOCK SOURCE
CLOCK SYNTHESIZER
Package Outline and Package Dimensions
(16 pin TSSOP, 4.40 mm Body, 0.65 mm Pitch)
Package dimensions are kept current with JEDEC Publication No. 95
16
Millimeters
Symbol
Min
Max
Inches
Min
Max
E1
IN D EX
AR EA
E
1
2
D
A
A1
A2
b
C
D
E
E1
e
L
α
aaa
--
1.20
0.05
0.15
0.80
1.05
0.19
0.30
0.09
0.20
4.90
5.1
6.40 BASIC
4.30
4.50
0.65 Basic
0.45
0.75
0°
8°
--
0.10
--
0.047
0.002
0.006
0.032
0.041
0.007
0.012
0.0035 0.008
0.193
0.201
0.252 BASIC
0.169
0.177
0.0256 Basic
0.018
0.030
0°
8°
--
0.004
A
2
A
1
A
c
-C -
e
b
S E A TIN G
P LA N E
L
aaa
C
Ordering Information
Part / Order Number
MK2746-01GLF
MK2746-01GLFT
Marking
274601GL
274601GL
Shipping Packaging
Tubes
Tape and Reel
Package
16 pin TSSOP
16 pin TSSOP
Temperature
0 to +70° C
0 to +70° C
"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 Device Technology (IDT) 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 IDT. IDT reserves the right to change any circuitry or specifications without notice. IDT
does not authorize or warrant any IDT product for use in life support devices or critical medical instruments.
IDT™
USB-DVR CLOCK SOURCE
5
MK2746-01
REV E 051310
模拟电子
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