June 2005

P2779A

rev 0.1

Low-Cost Notebook EMI Reduction IC

2 of 8

Notice: The information in this document is subject to change without notice.

Pin Configuration

Pin Description

Pin#

Pin Name

Type

Description

1

XIN / CLKIN

I

Connect to crystal or clock input.

2

XOUT

O

Crystal output.

3

PD

I

Power-down control pin. Pull low to enable power-down mode.

This pin has an internal pull-up resistor.

1

4

LF

I

External loop filter for the PLL. By changing the value of the CRC circuit,

the percentage spread can be adjusted accordingly.

(See Loop Filter Selection Table for detail values.)

5

VSS

P

Ground connection. Connect to system ground.

6

ModOUT

O

Spread spectrum clock output.

7

REF

O

Provides a reference clock output of the input frequency.

8

VDD

P

Connect to +3.3 V.

Note: 1. Connect to VDD if not used.

Loop Filter Selection Table VDD 3.3 V

BW = ± 0.50%

BW = ± 0.75%

BW = ± 1.00%

BW = ± 1.25%

Input

(MHz)

FS1

FS0

C1

(pF)

C2

(pF)

R1

(Ω)

C1

(pF)

C2

(pF)

R1

(Ω)

C1

(pF)

C2

(pF)

R1

(Ω)

C1

(pF)

C2

(pF)

R1

(Ω)

20

1

0

270

100,000

330

270

100,000

560

270

100,000

750

560

100,000

910

21-22

1

0

270

100,000

390

270

100,000

620

270

100,000

866(1%)

560

100,000

1,100

23-24

1

0

270

100,000

510

270

100,000

750

270

10,000

1,000

680

6,800

1,200

25-26

1

0

270

100,000

560

270

100,000

820

270

12,000

1,200

470

4,700

1,200

27-28

1

0

270

100,000

620

270

100,000

1,000

270

6,800

1,200

330

3,300

1,200

29-30

1

0

270

100,000

750

270

100,000

1,100

270

3,900

1,200

330

3,300

1,500

31-32

1

0

270

100,000

820

270

100,000

1,200

270

12,000

2,200

680

6,800

2,200

33-34

1

0

270

100,000

910

270

100,000

1,300

270

10,000

2,200

390

3,900

2,200

35-36

1

0

270

100,000

1,000

270

100,000

1,500

270

5,600

2,200

270

2,700

2,200

37-38

1

0

270

100,000

1,200

270

100,000

1,600

270

3,300

2,200

270

2,700

2,700

Please contact factory for loop filter values if desired spread settings are not listed.

C2

C1

R1

Pin 4 LF

REF

VSS

1

2

3

4

5

6

7

8

P2779A

XIN/ CLKIN

XOUT

PD

LF

VDD

ModOUT