Peak Reducing EMI Solution

2 of 7

September 2004

ASM3P2180A

rev 1.0

Notice: The information in this document is subject to change without notice.

Pin Diagram

Modulation Width Selection

SS%

Output

0

FIN

≥ FOUT ≥ FIN – 1.25%

1

FIN

≥ FOUT ≥ FIN – 2.4%

Frequency Range Selection

FS1

Modulation Rate

0

6

≤ FIN ≤10

1

18

≤ FIN ≤ 30

Pin Description

Pin#

Pin Name

Type

Description

1

CLKIN / X1

I

Crystal connection or external reference frequency input. This pin has

dual functions. It can be connected to either an external crystal or an

external reference clock.

2

NC / X2

O

Crystal connection. Connection for an external crystal. If using an

external reference, this pin must be left unconnected.

3

GND

P

Ground to entire chip.

4

SS%

I

Modulation width selection. When spread spectrum feature is turned

on, this pin is used to select the amount of variation and peak EMI

reduction that is desired on the output signal. Internal pull-up resistor.

5

CLKOUT

O

Output modulated frequency. Copy of the un-modulated input clock.

6

VDD

P

Power supply for the entire chip (3.3V).

7

FS1

I

Frequency selection bit 1. This pin selects the frequency range of

operation. (Refer to the Frequency Range Selection Table). This pin

has an internal pull-up resistor.

8

NC

-

No connect.

CLKOUT

NC

VDD

FS1

1

2

3

4

5

6

7

8

CLKIN / X1

NC / X2

GND

SS%

ASM3P2180A