W155 datasheet(2/6 Pages) CYPRESS

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W155

Pin Definitions

Pin Name

Pin No.

Pin Type

Pin Description

USBCLK/

SS%

I/O

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.

SYSCLK

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

ture is controlled by pins 9 & 14.

FS0:3

10, 8, 7, 5

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

the SYSCLK output.

SSON#

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

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

VDD

1, 6, 15

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

must be the same voltage level.

GND

4, 11, 13

Ground Connection: Connect to the common system ground plane.

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