MK2011

Fast Ethernet Clock Source

MDS 2011 B

2

Revision 120597

Printed 11/15/00

MicroClock Division of ICS•1271 Parkmoor Ave.•San Jose•CA•95126•(408)295-9800tel•(408)295-9818fax

I C R O

Number

Name

Type

Description

1

X1/ICLK

I

Crystal Connection. Connect to a 20.000 MHz crystal or clock.

2

VDD

P

Connect to +5V.

3

GND

P

Connect to ground.

4

25M

O

25.000 MHz clock output.

5

50M

O

50.000 MHz clock output.

6

GND

P

Connect to ground.

7

20M

O

20.000 MHz buffered crystal clock output.

8

X2

O

Crystal Connection to a 20.000 MHz crystal, or leave unconnected for clock input.

Pin Descriptions

Key: I = Input, O = output, P = power supply connection

Pin Assignment

20.00 MHz in

(crystal caps not

shown)

Pin 1

33

Ω (optional)

2

3

5

6

7

0.1µF

25MHz out

50MHz out

G

V

33

Ω (optional)

Suggested Layout

4

8

External Components/Crystal Selection

A minimum number of external components are required for proper oscillation. For a crystal input, one

22pF load capacitor should be connected to each of the X1 and X2 pins and ground, and a parallel

resonant 20.000 MHz, 16pF load, crystal is recommended. The frequency tolerance of the crystal should

be 50ppm or better. For a clock input, connect to X1 and leave X2 unconnected. A decoupling capacitor of

0.1µF should be connected between VDD and GND on pins 2 and 3, and 33

Ω terminating resistors

should be used on clock outputs with traces longer than 1 inch.

33

Ω (optional)

20MHz

out

1

8

2

3

4

7

6

5

X1/ICLK

20M

GND

X2

VDD

GND

50M

8 pin SOIC

25M