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MK2746-01
USB-DVR CLOCK
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. ICS manufacturers the largest variety of DVD, set top box, and multimedia clock synthesizers for all applications.
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
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
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MK2746-01 USB-DVR CLOCK SOURCE
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. decoupling 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 0.01mF should be connected between VDD and GND as close to the MK2746-01 as possible. For optimum device performance, the
Series Termination Resistor
When the PCB traces between the clock outputs and the loads are over 1 inch, series termination should be
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MK2746-01 USB-DVR CLOCK SOURCE
used. To series terminate a 50W trace (a commonly used trace impedance) place a 33W resistor in series with the clock line, as close to the clock output pin as possible. The nominal impedance of the clock output is 20W.
decoupling capacitor and VDD pin. The PCB trace to VDD pin should 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 33W 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. 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 0.01F 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
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK2746-01. 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
-0.5V to VDD+0.5V 0 to +70C -65 to +150C 260C
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
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MK2746-01 USB-DVR CLOCK SOURCE
DC Electrical Characteristics
VDD=3.3V 10% , Ambient temperature 0 to +70C, 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 VIH VIL VIH VIL VOH VOL VOH IDD IOS CIN ZOUT RPU RPD
Conditions
Min.
3.0 2.0
Typ.
Max.
3.6 0.8
Units
V V V V V V V V
ICLK ICLK IOH = -20 mA IOL = 20 mA IOH = -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
W
kW kW
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 tOR tOF tD tJ 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
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MK2746-01 USB-DVR CLOCK SOURCE
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 a 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
-Ce
b S E A T IN G P LAN E
L
aaa C
Ordering Information
Part / Order Number
MK2746-01G MK2746-01GT
Marking
MK2746-01G MK2746-01G
Shipping packaging
Tubes Tape and Reel
Package
16 pin TSSOP 16 pin TSSOP
Temperature
0 to +70 C 0 to +70 C
While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems (ICS) 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 ICS. ICS reserves the right to change any circuitry or specifications without notice. ICS does not authorize or warrant any ICS product for use in life support devices or critical medical instruments.
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