W185

2

Pin Definitions

Pin Name

Pin No.

Pin

Type

Pin Description

CLK0:5

9, 11, 12, 13,

15, 17

O

Modulated Frequency Outputs: Frequency modulated copies of the unmod-

ulated input clock (SSON# asserted).

CLKIN or X1

3

I

Crystal Connection or External Reference Frequency Input: This pin has

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

external reference clock.

NC or X2

4

I

Crystal Connection: If using an external reference, this pin must be left un-

connected.

SS%

6

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. This pin has an internal pull-up resistor.

Reset

23

I

Modulation Profile Restart: A rising edge on this input restarts the modulation

pattern at the beginning of its defined path. This pin has an internal pull-down

resistor.

REFOUT

1

O

Non-Modulated Output: This pin provides a copy of the reference frequency.

This output will not have the Spread Spectrum feature enabled regardless of

the state of logic input SSON#.

EN1:2

18, 7

I

Output Enable Select Pins: These pins control the activity of specific output

buffers. See Table 3 on page 1.

SSON#

24

I

Spread Spectrum Control (Active LOW): Asserting this signal (active LOW)

turns the internal modulation waveform on. This pin has an internal pull-down

resistor.

FS1:2

22, 2

I

Frequency Selection Bit 1 and 2: These pins select the frequency of opera-

tion. Refer to Table 1. These pins have internal pull-up resistors.

VDD

10, 16, 20, 21

P

Power Connection: Connected to 3.3V or 5V power supply.

GND

5, 8, 14

G

Ground Connection: This should be connected to the common ground plane.

NC

19

NC

No Connect: This pin should be left floating.