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CY25818/19

Document #: 38-07362 Rev. *B

Page 2 of 7

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Overview

The Cypress CY25818/19 products are Spread Spectrum
Clock Generator (SSCG) ICs used for the purpose of reducing
EMI found in today’s high-speed digital electronic systems.
The devices use a Cypress proprietary phase-locked loop
(PLL) and Spread Spectrum Clock (SSC) technology to
synthesize and modulate the frequency of the input clock. By
frequency modulating the clock, the measured EMI at the
fundamental and harmonic frequencies is greatly reduced.
This reduction in radiated energy can significantly reduce the
cost of complying with regulatory agency requirements and
improve time to market without degrading system perfor-
mance.

The input frequency range is 8–16 MHz for the CY25818 and
16–32 MHz for the CY25819. Both products accept external
clock, crystal, or ceramic resonator inputs.

The CY25818/19 provide separate modulated (SSCLK) and
unmodulated reference (REFCLK) clock outputs which are the
same frequency as the input clock frequency. Down spread
frequency modulation can be selected by the user, based on
three discrete values of Spread%. A separate power down
function is also provided.

The CY25818/19 products are available in an 8-pin SOIC
(150-mil) package with a commercial operating temperature
range of 0–70

°

C. Contact Cypress for availability of –40 to

+85

°

C industrial temperature range operation or TSSOP

package versions. Refer to the CY25568, CY25811,
CY25812, and CY25814 products for other functions such as
clock multiplication of 1×, 2×, or 4× to generate a wide range
of Spread Spectrum output clocks from 4 to 128 MHz.

Input Frequency Range and Selection

CY25818/19 input frequency range is 8–32 MHz. This range
is divided into two segments, as given in 

Table 1

Spread% Selection

CY25818/19 SSCG products provide Down-Spread frequency
modulation. The amount of Spread% is selected by using
3-Level S0 digital input. Spread% values are given in 

Table 2

.

Pin Description

Pin

Name

Description

1

XIN/CLK

Clock, Crystal, or Ceramic Resonator Input Pin.

2

Vss

Power Supply Ground.

3

S0

Digital Spread% Control Pin. 3-Level input (H-M-L). Default = M.

4

SSCLK

Modulated Spread Spectrum Output Clock. The output frequency is referenced to input frequency. Refer 
to 

Table 2

 for the amount of modulation (Spread%).

5

REFCLK

Unmodulated Reference Clock Output. The unmodulated output frequency is the same as the input 
frequency.

6

PD#

Power-Down Control Pin. Default = H (Vdd).

7

Vdd

Positive Power Supply.

8

XOUT

Clock, Crystal, or Ceramic Resonator Output Pin. Leave this pin unconnected if an external clock is used 
at X

IN

 pin.

Table 1. Input and Output Frequency Selection

Product

Input/Output Frequency Range

CY25818

8–16 MHz

CY25819

16–32 MHz

Table 2. Spread% Selection

XIN (MHz)

Product

S0 = 1

S0 = 0

S0 = M

Down (%)

Down (%)

Down (%)

8–10

CY25818

–3.0

–2.2

–0.7

10–12

CY25818

–2.7

–1.9

–0.6

12–14

CY25818

–2.5

–1.8

–0.6

14–16

CY25818

–2.3

–1.7

–0.5

16–20

CY25819

–3.0

–2.2

–0.7

20–24

CY25819

–2.7

–1.9

–0.6

24–28

CY25819

–2.5

–1.8

–0.6

28–32

CY25819

–2.3

–1.7

–0.5

[+] Feedback 

Содержание CY25818

Страница 1: ...3 mW typ 32 MHz Low cycle to cycle jitter SSCLK 250 ps typ REFOUT 275 ps typ Available in 8 pin 150 mil SOIC package Applications Printers and MFPs LCD panels and notebook PCs Digital copiers PDAs Aut...

Страница 2: ...versions Refer to the CY25568 CY25811 CY25812 and CY25814 products for other functions such as clock multiplication of 1 2 or 4 to generate a wide range of Spread Spectrum output clocks from 4 to 128...

Страница 3: ...iven by the following formula fmod fIN DR where fmod is the Modulation Rate fIN is the Input Frequency and DR is the Divider Ratio as given in Table 3 Maximum Ratings 1 2 Supply Voltage Vdd 5 5V Input...

Страница 4: ...CLK and REFCLK 0 4V to 2 4V 2 0 3 0 4 0 ns tfall1 Clock Fall Time SSCLK and REFCLK 0 4V to 2 4V 2 0 3 0 4 0 ns CDCin Input Clock Duty Cycle XIN 20 50 80 CDCout Output Clock Duty Cycle SSCLK and REFCLK...

Страница 5: ...cs This results in additional EMI reduction in electronic systems Application Schematic Notes 3 XIN 16 0 MHz S0 1 SSCLK 16 0 MHz BW 2 14 4 Xin 32 0MHz S0 1 SSCLK 32 0 MHz BW 2 15 Figure 6 CY25818 Spre...

Страница 6: ...awing and Dimensions All product and company names mentioned in this document may be the trademarks of their respective holders Ordering Information Part Number Package Type Product Flow CY25818SC 8 p...

Страница 7: ...18 19 Spread Spectrum Clock Generator Document Number 38 07362 REV ECN NO Issue Date Orig of Change Description of Change 112462 03 21 02 OXC New Data Sheet A 122701 12 28 02 RBI Added power up requir...

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