I2784A-08ST - Alliance Semiconductor

July 2005 P2781/82/84

rev 1.5

Alliance Semiconductor

2575, Augustine Drive • Santa Clara, CA • Tel: 408.855.4900 • Fax: 408.855 .4999 • www.alsc.com

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

General Purpose EMI Reduction IC

Features

 Provides up to 15dB of EMI suppression

 FCC approved method of EMI attenuation

 Generates a 1X, 2X, and 4X low EMI spread

spectrum clock of the input frequency

 Input frequency range from 3 to 78MHz

 External loop filter for spread % adjustment

 Spreading ranges from ±0.25% to ±5.0%

 Ultra low cycle-to-cycle jitter

 Zero-cycle slip

 3.3V operating voltage range

 10 mA output drives

 TTL or CMOS compatible outputs

 Ultra-low power CMOS design

 P278XA is available in 8 pin SOIC and TSSOP

Packages

 Available for industrial and automotive

temperature ranges.

Product Description

The P278xA is a versatile spread spectrum frequency

modulator designed specifically for digital camera and

other digital video and imaging applications. The P278xA

reduces electromagnetic interference (EMI) at the clock

source, which provides system wide reduction of EMI of

all clock dependent signals. The P278xA allows

significant system cost savings by reducing the number of

circuit board layers and shielding that are traditionally

required to pass EMI regulations.

The P278xA uses the most efficient and optimized

modulation profile approved by the FCC. The P278xA

modulates the output of a single PLL in order to “spread”

the bandwidth of a synthesized clock and, more

importantly, decreases the peak amplitudes of its

harmonics. This results in significantly lower system EMI

compared to the typical narrow band signal produced by

oscillators and most frequency generators. Lowering EMI

by increasing a signal’s bandwidth is called spread

spectrum clock generation.

Applications

The P278xA is targeted towards MFP, xDSL, fax modem,

set-top box, USB controller, DSC, and embedded systems.

Block Diagram

Crystal

Oscillator

Frequency

Divider

Feedback

Divider

Phase

Detector

Modulation

Output

Divider

VCO

XIN /CLKIN

XOUT

FS0 FS1 LF VDD

VSS

PLL

ModOUT

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

Pin Configuration

Pin Description (P278XA)

Pin# Pin Name Type Description

1 XIN/CLKIN I Connect to crystal or clock input. This pin has dual functions. It can be connected

either to an external crystal or an external reference clock.

2 XOUT O Crystal connection. If using an external reference, this pin must be left

unconnected.

3 FS1 I

Digital logic input used to select input frequency range

(see the Input Frequency Selection Table). This pin has an internal pull-up

resistor.

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 the Loop Filter Selection

Table for detail value.

5 VSS I Ground Connection. Connect to system ground.

6 ModOUT O Spread Spectrum Clock Output.

7 FS0 I

Digital logic input used to select input frequency range

(see the Input Frequency Selection Table). This pin has an internal pull-up

resistor.

8 VDD P Connect to +3.3 V

Input Frequency Selection Table

Output Frequency Scaling (MHz)

FS1 FS0 Input (MHz) P2781A P2782A P2784A Modulation Rate (KHz)

0 0 3 to 9 3 to 9 6 to 18 12 to 36 Fin / 128

0 1 10 to 19 10 to 19 20 to 38 40 to 76 Fin / 256

1 0 20 to 38 20 to 38 40 to 76 80 to 152 Fin / 512

1 1 39 to 78 39 to 78 78 to 156 156 to 312 Fin / 1024

1

2

3

4

8

7

6

5

XIN / CLKIN

XOUT

FS1

LF

VDD

FS0

ModOUT

VSS

P278XA-08S

P278XA-08T

Standard pin Configuration offered in both

8 pin SOIC and TSSOP Packages

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

Loop Filter Selection Table VDD 3.3V

Contact Alliance for loop values that are not listed in the table and for component

selection values for industrial and automotive temperatures.

BW = ±0.50%1 BW = ±0.75%1 BW = ±1.00%1 BW = ±1.25%1

Input

MHz FS1 FS0 C1

(pF) C2

(pF) R1

(ohm) C1

(pF) C2

(pF) R1

(ohm) C1

(pF) C2

(pF) R1

(ohm) C1

(pF) C2

(pF) R1

(ohm)

3 0 0 270 330,000 220 270 330,000 300 270 100,000 390 560 100,000 510

4 0 0 270 100,000 270 270 100,000 390 270 100,000 560 560 100,000 680

5 0 0 270 100,000 390 270 100,000 560 270 100,000 750 560 100,000 910

6 0 0 270 100,000 510 270 100,000 750 270 10,000 1,000 680 6,800 1,200

7 0 0 270 100,000 620 270 100,000 1,000 270 5,600 1,200 330 3,300 1,200

8 0 0 270 100,000 820 270 100,000 1,200 270 12,000 2,200 680 6,800 2,200

9 0 0 270 100,000 1,000 270 100,000 1,500 270 5,600 2,200 270 2,700 2,200

10 0 1 270 100,000 330 270 100,000 510 270 100,000 750 560 100,000 910

11 0 1 270 100,000 390 270 100,000 560 270 100,000 866(1%) 560 100,000 1,100

12 0 1 270 100,000 510 270 100,000 750 270 10,000 1,000 680 6,800 1,200

13 0 1 270 100,000 560 270 100,000 820 270 12,000 1,200 470 4,700 1,200

14 0 1 270 100,000 620 270 100,000 1,000 270 5,600 1,200 330 3,300 1,200

15 0 1 270 100,000 750 270 100,000 1,100 270 3,900 1,200 330 3,300 1,500

16 0 1 270 100,000 820 270 100,000 1,200 270 12,000 2,200 680 6,800 2,200

17 0 1 270 100,000 910 270 100,000 1,300 270 10,000 2,200 390 3,900 2,200

18 0 1 270 100,000 1,000 270 100,000 1,500 270 5,600 2,200 270 2,700 2,200

19 0 1 270 100,000 1,200 270 100,000 1,600 270 3,300 2,200 270 2,700 2,700

20 0 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

39-42 1 1 270 100,000 330 270 100,000 560 270 100,000 750 560 100,000 910

43-46 1 1 270 100,000 390 270 100,000 620 270 100,000 866 (1%) 560 100,000 1,100

47-50 1 1 270 100,000 510 270 100,000 750 270 10,000 1,000 680 6,800 1,200

51-54 1 1 270 100,000 560 270 100,000 820 270 12,000 1,200 470 4,700 1,200

55-58 1 1 270 100,000 620 270 100,000 1,000 270 6,800 1,200 330 3,300 1,200

59-62 1 1 270 100,000 750 270 100,000 1,100 270 3,900 1,200 330 3,300 1,500

63-66 1 1 270 100,000 820 270 100,000 1,200 270 12,000 2,200 680 6,800 2,200

67-70 1 1 270 100,000 910 270 100,000 1,300 270 8,200 2,200 390 3,900 2,200

71-74 1 1 270 100,000 1,000 270 100,000 1,600 270 5,600 2,200 270 2,700 2,200

75-78 1 1 270 100,000 1,200 270 100,000 1,800 270 3,300 2,200 270 2,700 2,700

1 The BW value is representative of typical conditions

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

Spread Spectrum Selection

The P278xA performs Zero Cycle Slip when set at low percentage spreading. This allows no occurrence of system timing

error. The optimal setting should minimize system EMI to the fullest without affecting system performance. The spreading is

described as a percentage deviation of the center frequency.

(Note: the center frequency is the frequency of the external reference input on CLKIN, Pin 1.)

The P2781A is designed for PC peripheral, networking, notebook PC, and LCD monitor applications. It is optimized for

operation between 3 to 78MHz range. In the following application schematic example, the P2781A spread percentage

selection is determined by the external LF value specified in the Loop Filter Selection Table. The Input Frequency Selection

Table specifies the input frequency range. The external LF allows the user to fine tune the spread percentage to optimize the

EMI reduction benefits of the spread spectrum.

Note: Both logic input pins FS1 and FS0 have to be connected to either VDD or VSS. Do not leave them floating.

1

2

3

4

8

7

6

5

VDD

FS0

ModOUT

VSSLF

FS1

XOUT

XIN/CLKIN

P2781A

+3.3V

Modulated 16MHz Clock

To target Chip

16 MHz

0.1µF

C2 C1

R1

0 Ohm

2.2 K

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

Absolute Maximum Ratings

Symbol Parameter Rating Unit

VDD Supply voltage, DC (VSS – 0.5) to 7 V

VI Input voltage, DC (VSS-0.5) to (VDD+0.5) V

VO Output voltage, DC (VSS-0.5) to (VDD + 0.5) V

IIK Input clamp current (VI<0 or VI>VDD) -50 to +50 mA

IOK Output clamp current (VI<0 or VI>VDD) -50 to +50 mA

TS Storage temperature -65 to +125 °C

TA Ambient temperature range, under bias -55 to 125 °C

TJ Junction temperature 150 °C

Lead temperature (soldering 10 sec) 260 °C

Input static discharge voltage protection

(As per JEDEC STD22- A114-B) 2 kV

Note: These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for extended periods may affect device

reliability.

DC Electrical Characteris tics

(Test condition: All parameters are measured at room temperature (+25°C) unless otherwise stated)

Symbol Parameter Min Typ Max Unit

VIL Input low voltage VSS – 0.3 - 0.8 V

VIH Input high voltage 2.0 - VDD +0.3 V

IIL Input low current

(internal input pull-up resistor on FS0 and FS1) - 60 - µA

IIH Input high current

(internal input pull-up resistor on FS0 and FS1) - 60 - µA

IXOL XOUT output low current - 10 - mA

IXOH XOUT output high current - 10 - mA

VOL Output low voltage (VDD = 3.3V, IOL = 20mA) - - 0.4 V

VOH Output high voltage (VDD = 3.3V, IOH = 20mA) 2.5 - - V

IDD Static supply current - 3 - mA

ICC Typical dynamic supply current

(25pF scope probe loading) 5.2 at 3MHz - 21.2 at 82MHz mA

VDD Operating voltage 3.0 3.3 3.6 V

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

AC Electrical Characteris tics

Symbol Parameter Min Typ Max Unit

fIN Input frequency: P278XA 3 - 78 MHz

fOUT Output frequency:

P2781A

P2782A

P2784A

3

6

12

-

78

156

312

MHz

tLH

P278XA

Output rise time (measured at 0.8 V to 2.0 V,

25pF scope probe loading) - 1 - nS

tHL

P278XA

Output fall time (measured at 2.0 V to 0.8 V, 25

pF scope probe loading) - 1 - nS

tJC

P2781A

Jitter (cycle to cycle, ± 6sigma, 1000 sweeps,

± 0.5% spread, I/O frequency = 16MHz) - ±250 - pS

tD

P2781A

Output duty cycle deviation (error from 50% duty

cycle, 25pF scope probe loading) ±1 at 3MHz - ±2 at 82MHz %

∆F

P278XA

Frequency deviation tolerance from BW% stated

in the Loop Filter Selection Table -20 0 +20 %

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

Package Information

Mechanical Package Outline 8-Pin SOIC Package

D

EH

D

A1

A2

A

θ

L

C

B

e

Dimensions

Inches Millimeters

Symbol

Min Max Min Max

A1 0.004 0.010 0.10 0.25

A 0.053 0.069 1.35 1.75

A2 0.049 0.059 1.25 1.50

B 0.012 0.020 0.31 0.51

C 0.007 0.010 0.18 0.25

D 0.193 BSC 4.90 BSC

E 0.154 BSC 3.91 BSC

e 0.050 BSC 1.27 BSC

H 0.236 BSC 6.00 BSC

L 0.016 0.050 0.41 1.27

θ 0° 8° 0° 8°

Note: Controlling dimensions are millimeters

SOIC - 0.074 grams unit weight

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

E

H

A

A1

A2

D

B

C

L

θ

e

Mechanical Package Outline 8-Pin TSSOP Package

Dimensions

Inches Millimeters

Symbol

Min Max Min Max

A 0.043 1.10

A1 0.002 0.006 0.05 0.15

A2 0.033 0.037 0.85 0.95

B 0.008 0.012 0.19 0.30

c 0.004 0.008 0.09 0.20

D 0.114 0.122 2.90 3.10

E 0.169 0.177 4.30 4.50

e 0.026 BSC 0.65 BSC

H 0.252 BSC 6.40 BSC

L 0.020 0.028 0.50 0.70

θ 0° 8° 0° 8°

Note: Controlling dimensions are millimeters

TSSOP - 0.0325 grams unit weight

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

Ordering Codes

Ordering # Marking Package Type QTY / Reel Temperature

P278XA-08ST P278XA 8 PIN SOIC, TUBE See flow

P278XA-08SR P278XA 8 PIN SOIC, TAPE & REEL 2,500 See flow

P278XA-08TT P278XA 8 PIN TSSOP, TUBE See flow

P278XA-08TR P278XA 8 PIN TSSOP, TAPE & REEL 2,500 See flow

P278XAF-08ST P278XAF 8 PIN SOIC, TUBE, Pb Free See flow

P278XAF-08SR P278XAF 8 PIN SOIC, TAPE AND REEL,Pb Free 2,500 See flow

P278XAF-08TT P278XAF 8 PIN TSSOP, TUBE, Pb Free See flow

P278XAF-08TR P278XAF 8 PIN TSSOP, TAPE AND REEL, Pb Free 2,500 See flow

P278XAG-08ST P278XAG 8 PIN SOIC, TUBE, Green See flow

P278XAG-08SR P278XAG 8 PIN SOIC, TAPE AND REEL, Green 2,500 See flow

P278XAG-08TT P278XAG 8 PIN TSSOP, TUBE, Green See flow

P278XAG-08TR P278XAG 8 PIN TSSOP, TAPE AND REEL, Green 2,500 See flow

I278XA-08ST I278XA 8 PIN SOIC, TUBE See flow

I278XA-08SR I278XA 8 PIN SOIC, TAPE & REEL 2,500 See flow

I278XA-08TT I278XA 8 PIN TSSOP, TUBE See flow

I278XA-08TR I278XA 8 PIN TSSOP, TAPE & REEL 2,500 See flow

I278XAF-08ST I278XAF 8 PIN SOIC, TUBE, Pb Free See flow

I278XAF-08SR I278XAF 8 PIN SOIC, TAPE AND REEL,Pb Free 2,500 See flow

I278XAF-08TT I278XAF 8 PIN TSSOP, TUBE, Pb Free See flow

I278XAF-08TR I278XAF 8 PIN TSSOP, TAPE AND REEL, Pb Free 2,500 See flow

I278XAG-08ST I278XAG 8 PIN SOIC, TUBE, Green See flow

I278XAG-08SR I278XAG 8 PIN SOIC, TAPE AND REEL, Green 2,500 See flow

I278XAG-08TT I278XAG 8 PIN TSSOP, TUBE, Green See flow

I278XAG-08TR I278XAG 8 PIN TSSOP, TAPE AND REEL, Green 2,500 See flow

X278XA-08ST X278XA 8 PIN SOIC, TUBE See flow

X278XA-08SR X278XA 8 PIN SOIC, TAPE & REEL 2,500 See flow

X278XA-08TT X278XA 8 PIN TSSOP, TUBE See flow

X278XA-08TR X278XA 8 PIN TSSOP, TAPE & REEL 2,500 See flow

X278XAF-08ST X278XAF 8 PIN SOIC, TUBE, Pb Free See flow

X278XAF-08SR X278XAF 8 PIN SOIC, TAPE AND REEL, Pb Free 2,500 See flow

X278XAF-08TT X278XAF 8 PIN TSSOP, TUBE, Pb Free See flow

X278XAF-08TR X278XAF 8 PIN TSSOP, TAPE AND REEL, Pb Free 2,500 See flow

X278XAG-08ST X278XAG 8 PIN SOIC, TUBE, Green See flow

X278XAG-08SR X278XAG 8 PIN SOIC, TAPE AND REEL, Green 2,500 See flow

X278XAG-08TT X278XAG 8 PIN TSSOP, TUBE, Green See flow

X278XAG-08TR X278XAG 8 PIN TSSOP, TAPE AND REEL, Green 2,500 See flow

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

Device Ordering Information

P278XA F- 08 XX

Licensed under US patent #5,488,627, #6,646,463 and #5,631,920

Package:

ST – SOIC, TUBE

SR - SOIC, T/R

TT – TSSOP, TUBE

TR - TSSOP, T/R

DEVICE NUMBER

Flow:

P = Commercial Temperature Range (0°C to 70°C)

I = Industrial Temperature Range (-40°C to 85°C)

X = Automotive Tem

p

erature Ran

g

e

(

-40°C to 125°C

)

Pin Count

F = LEAD FREE or RoHS COMPLIANT PART

G = GREEN

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

trademarks or registered trademarks of Alliance. All other brand and product names may be the trademarks of their

respective companies. Alliance reserves the right to make changes to this document and its products at any time without

notice. Alliance assumes no responsibility for any errors that may appear in this document. The data contained herein

represents Alliance's best data and/or estimates at the time of issuance. Alliance reserves the right to change or correct this

data at any time, without notice. If the product described herein is under development, significant changes to these

specifications are possible. The information in this product data sheet is intended to be general descriptive information for

potential customers and users, and is not intended to operate as, or provide, any guarantee or warrantee to any user or

customer. Alliance does not assume any responsibility or liability arising out of the application or use of any product

described herein, and disclaims any express or implied warranties related to the sale and/or use of Alliance products

including liability or warranties related to fitness for a particular purpose, merchantability, or infringement of any intellectual

property rights, except as express agreed to in Alliance's Terms and Conditions of Sale (which are available from Alliance).

All sales of Alliance products are made exclusively according to Alliance's Terms and Conditions of Sale. The purchase of

products from Alliance does not convey a license under any patent rights, copyrights; mask works rights, trademarks, or any

other intellectual property rights of Alliance or third parties. Alliance does not authorize its products for use as critical

components in life-supporting systems where a malfunction or failure may reasonably be expected to result in significant

injury to the user, and the inclusion of Alliance products in such life-supporting systems implies that the manufacturer

assumes all risk of such use and agrees to indemnify Alliance against all claims arising from such use.

Alliance Semiconductor Corporation

2575, Augustine Drive,

Santa Clara, CA 95054

Tel# 408-855-4900

Fax: 408-855-4999

www.alsc.com

Part Number: P2781/82/84

Document Version: 1.5

Note: This product utilizes US Patent # 6,646,463 Impedance Emulator Patent issued to Alliance Semiconductor, dated 11-11-2003