MK2746G Datasheet MK2746G, MK2746GTR | P1-P3

DATASHEET

DVD/MPEG CLOCK SOURCE MK2746

IDT™

DVD/MPEG CLOCK SOURCE 1

MK2746 REV B 122109

Description

The MK2746 is a low cost, low jitter, high performance clock

synthesizer for DVD and other MPEG2 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 including the

processor clock, audio clock, bus driver clock, SDRAM

clock and a Video clock. The audio clocks are frequency

locked to the 27 MHz input using our patented zero ppm

error techniques, allowing audio and video to track exactly,

thereby eliminating the need for large buffer memory.

IDT manufacturers the largest variety of DVD, set top box,

and multimedia clock synthesizers for all applications.

Block Diagram

Features

• Packaged in 16 pin TSSOP

• Operating voltage of 3.3 V

• Provides tight jitter controlled selectable processor clock

per table.

• Provides selectable audio clock per table.

• Provides fixed outputs of 27 MHz (Video), 50 MHz

(DSP/Bus clock) and 133.33 MHz (SDRAM).

• Advanced, low power, sub-micron CMOS process

NOTE: EOL for non-green parts to occur on 5/13/10

per PDN U-09-01

27M Video Clock

Clock Buffer/

Crystal

Ocsillator

PS1:0

133.33 M SDRAM Clock

Processor

(Tight Jitter)

VDD

GND

PLL / Clock

Circuit

50M Bus Clock

Audio

AS1:0

27 MHz crystal

or clock

MK2746

DVD/MPEG CLOCK SOURCE VCXO AND SYNTHESIZER

IDT™

DVD/MPEG CLOCK SOURCE 2

MK2746 REV B 122109

Pin Assignment Clock Output Select Table in MHz

0 = connect directly to GND

1 = connect directly to VDD

Pin Descriptions

VDD

X1/ICLK

VDD

27M

GND

AS0

PCLK

PS0

ACLK

AS1

VDD

133.33M

GND

PS1

50M

16 pin (173 mil) TSSOP

AS1 AS0 Audio CLK

0 0 12.288

0 1 11.2896

1 0 18.432

1 1 8.192

PS1 PS0 Processor

CLK

00 66.66

01 41.66

10 50

11 58.33

Number

Name

Type

Pin Description

1 X2 Input Connect to a 27 MHz fundamental mode crystal. Leave open for clock input.

2 X1/ICLK Input Connect to a 27 MHz fundamental mode crystal or clock.

3 VDD Power Connect to +3.3 V.

4 GND Power Connect to ground

5 PCLK Output Processor clock output. Determined by the status of PS1, PS0 per table

above.

6 PS0 Input Processor Clock select 0. Selects processor clock per table above.

7 133.33M Output SDRAM clock output.

8 PS1 Input Processor Clock select 1. Selects processor clock per table above.

9 50M Output 50 MHz clock output.

10 GND Power Connect to ground.

11 VDD Power Connect to +3.3 V.

12 AS1 Input Audio clock select 1. Selects audio clock per table above.

13 ACLK Output Audio clock output determined by the status of PS1, PS0.

14 AS0 Input Audio clock select 0. Selects audio clock per table above.

15 27M Output 27 MHz clock output.

16 VDD Power Connect to +3.3 V.

MK2746

DVD/MPEG CLOCK SOURCE VCXO AND SYNTHESIZER

IDT™

DVD/MPEG CLOCK SOURCE 3

MK2746 REV B 122109

External Component Selection

The MK2746 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 MK2746 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.

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.

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 18 pF

load capacitance, each crystal capacitor would be 24 pF

[(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

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. This includes signal traces just

underneath the device, or on layers adjacent to the ground

plane layer used by the device.

Absolute Maximum Ratings

Stresses above the ratings listed below can cause permanent damage to the MK2746. 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 Rating

Supply Voltage, VDD 7 V

All Inputs and Outputs -0.5 V to VDD+0.5 V

Ambient Operating Temperature 0 to +70° C

Storage Temperature -65 to +150° C

Soldering Temperature 260° C

P1-P3 P4-P6

MK2746G

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MK2746G

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