CY25404

Document #: 001-43258 Rev. *C

Page 4 of 13

General Description

Four Configurable PLLs

The CY25404 has four programmable PLLs that can be used to

generate output frequencies ranging from 3 to 166 MHz. The

advantage of having four PLLs is that a single device generates

up to four independent frequencies from a single crystal.

Input Reference Clocks

The input to the CY25404 can be either a crystal or a clock

signal. The input frequency range for crystals is 8 MHz to 48

MHz, while that for clock signals is 8 MHz to 166 MHz. The

required voltage level for the input reference clock (EXCLKIN) is

shown in the DC and AC Electrical Specification tables.

This device has programmable power supply option and it can

be programmed to operate at any voltage 2.5 V, 3.0 V, or 3.3 V.

Output Bank Settings

There are nine clock outputs grouped in three output driver

banks. The Bank 1, Bank 2, and Bank 3 correspond to (CLK1,

CLK2, CLK3), (CLK4, CLK5, CLK6), and (CLK7, CLK8, CLK9)

respectively. Separate power supplies are used for each of these

banks and they can be any of 2.5 V, 3.0 V, or 3.3 V. These

multiple choice of output clock voltage levels.

Output Source Selection

These devices have programmable input sources for each of its

nine clock outputs (CLK1–9). There are five available clock

sources for these outputs. These clock sources are:

XIN/EXCLKIN, PLL1, PLL2, PLL3, or PLL4. Output clock source

selection is done using four out of five crossbar switch. Thus, any

one of these five available clock sources can be arbitrarily

selected for the clock outputs. This gives user a flexibility to have

up to four independent clock outputs.

Spread Spectrum Control

Two of the four PLLs (PLL3 and PLL4) have spread spectrum

capability for EMI reduction in the system. The device uses a

Cypress proprietary PLL and spread spectrum clock (SSC)

technology to synthesize and modulate the frequency of the PLL.

The spread spectrum feature can be turned on or off using a

multifunction control pin (CLK7/SSON). It can be programmed to

either center spread range from ±0.125% to ±2.50% or down

spread range from –0.25% to –5.0% with Lexmark or Linear

profile.

Frequency Select

There are three multifunction frequency select pins (FS0, FS1

and FS2) that provide an option to select eight different sets of

frequencies among each of the four PLLs. Each output has

programmable output divider options.

Glitch-Free Frequency Switch

When the frequency select pin (FS) is used to switch frequency,

the outputs are glitch-free provided frequency is switched using

output dividers. This feature enables uninterrupted system

operation while clock frequency is being switched.

Output Enable Mode

There is a multifunction programmable pin 10, OE/FS1 that can

be programmed to operate as output enable (OE) mode. OE is

a high-true input and individual clock outputs can be

programmed to be sensitive to this OE pin. If activated it shuts

off the output drivers, resulting in minimum power consumption

for the device.

Output Drive Strength

The DC drive strength of the individual clock output can be

and fall times for different drive strength settings.

Generic Configuration and Custom Frequency

There is a generic set of output frequencies available from the

factory that can be used for the device evaluation purposes. The

device, CY25404 can be custom programmed to any desired

frequencies and listed features. For customer specific

programming, please contact local cypress field application

engineer (FAE) or sales representative.

Table 2. Output Drive Strength

Output Drive Strength

Rise/Fall Time (ns)

(Typical Value)

Low

6.8

Mid Low

3.4

Mid High

2.0

High

1.0