IMIFS741 データシートの表示（PDF） - Unspecified

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IMIFS741

Low EMI Spectrum Spread Clock

Unspecified 

Approved Product

FS741

Low EMI Spectrum Spread Clock

SSCG Modulation Profile

The modulation rate of the FS741 is determined by the input frequency and the operating range. The input

frequency is divided by a fixed number, depending on the operating range

that is selected. The modulation rate of the FS741 can be determined from

the chart at the right.

Xin Range

4 - 8 MHz

Mod. rate

divider

60

Example:

Freq. of Xin = 25 MHz

Operating Range = 16 - 40 MHz

Modrate = Fxin/240 = 104.166 Khz.

8 - 16 MHz

120

16 - 40 MHz

240

40 - 68 MHz

480

Table 8

With the correct loop filter connected to pin 4, the following profile will provide the best EMI reduction. This profile

can be seen on a Time Domain Analyzer.

+ .5%

1.0% Xin

Total

Fc = 25 MHz

- .5%

Modrate = 104.166 Khz

1.92

3.84

5.76

7.68

9.60

11.52

TIME (microseconds)

13.44

15.36

17.28

19.20

Figure 5. Frequency Profile in Time Domain

International Microcircuits, Inc.

525 Los Coches St., Milpitas, 95035 408-263-6300, FAX 408-263-6571

http:/www.imicorp.com

4/5/1999

Rev. 2.1

Page 9 of 16

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