W155 查看數據表（PDF） - Cypress Semiconductor

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产品描述 (功能)

比赛名单

W155

Spread Spectrum Frequency Timing Generator

Cypress Semiconductor 

W155

Pin Definitions

Pin Name

Pin No.

USBCLK/

14

SS%

SYSCLK

FS0:3

SSON#

X1

X2

TEST

VDD

GND

12

10, 8, 7, 5

9

2

3

16

1, 6, 15

4, 11, 13

Pin Type

I/O

O

I

I

I

I

I

P

G

Pin Description

USB Clock Output/Modulation Width Selection Input: When an input; if spread

spectrum feature is enabled, this pin is used to select the amount of frequency

variation on the SYSCLK output (see Table 2). Wider variations result in greater

peak EMI reduction. When an output: supplies a non-spread 48-MHz signal for

USB support.

System Clock Output: Frequency is selected per Table 1. Spread spectrum fea-

ture is controlled by pins 9 & 14.

Frequency Select Pins: These pins set the frequency of the signal provided at

the SYSCLK output.

Spread Spectrum Control (active LOW): Pulling this input signal HIGH turns the

internal modulating waveform off. This pin has an internal pull-down resistor.

Crystal Connection or External Reference Frequency Input: This pin has dual

functions. It can be used as either an external crystal connection, or as an external

reference frequency input.

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

nected.

Test Mode: For normal operation, tie this pin to ground.

Power Connection: Connected to either 3.3V or 5.0V power supply. All VDD pins

must be the same voltage level.

Ground Connection: Connect to the common system ground plane.

2

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