A2184A-08SR - Alliance Semiconductor

October 2003 P2781/82/84

rev 1.0

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 15 dB 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 78 MHz

 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

 Available in 8 pin SOIC and TSSOP

 Available for industrial and automotive

temperature ranges.

Product Description

The P278xx is a versatile spread spectrum

frequency modulator designed specifically for digital

camera and other digital video and imaging

applications. The P278xx reduces electromagnetic

interference (EMI) at the clock source, which

provides system wide reduction of EMI of all clock

dependent signals. The P278xx allows significant

system cost savings by reducing the number of

circuit board layers and shielding that are

traditionally required to pass EMI regulations.

The P278xx uses the most efficient and

optimized modulation profile approved by the

FCC.

The P278xx 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 P278xx is targeted towards MFP, xDSL, fax

modem, set-top box, USB controller, DSC, and

embedded systems.

Block Diagram

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 2 of 9

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.

2 XOUT I Crystal output

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) P2781X P2782X P2784X 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

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 3 of 9

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)

(ohm)

(pF)

(ohm)

(pF)

(ohm)

(pF)

(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

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 4 of 9

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 78 MHz 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.

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 5 of 9

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

Absolute Maximum Ratings

Symbol Parameter Rating Unit

VDD, VIN Voltage on any pin with respect to GND -0.5 to + 7.0 V

TSTG Storage temperature -65 to +125 °C

TA Operating temperature 0 to +70 °C

DC Electrical Characteristics

Symbol Parameter Min Typ Max Unit

VIL Input low voltage GND – 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) – 0 – µA

IXOL XOUT output low current – 10 – mA

IXOH XOUT output high current – 10 – mA

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

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

IDD Static supply current - 3 - mA

ICC Typical dynamic supply current (25 pF scope probe

loading) 5.2 at 3 MHz – 21.2 at 82 MHz mA

VDD Operating voltage 3.0 3.3 3.6 V

AC Electrical Characteristics

Symbol Parameter Min Typ Max Unit

fIN Input frequency: P278XX 3 78 MHz

fOUT Output frequency:

P2781X

P2782X

P2784X

156

312

MHz

tLH

P278XX

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

25 pF scope probe loading) 1 ns

tHL

P278XX

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

25 pF scope probe loading) 1 ns

tJC

P2781X

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

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

P2781X

Output duty cycle deviation (error from 50%

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

∆F

P278XX

Frequency deviation tolerance from BW%

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

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 6 of 9

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

Package Information

Mechanical Package Outline 8-Pin SOIC

Dimensions in inches Dimensions in millimeters

Symbol Min Nor Max Min Nor Max

A 0.057 0.064 0.071 1.45 1.63 1.80

A1 0.004 0.007 0.010 0.10 0.18 0.25

A2 0.053 0.061 0.069 1.35 1.55 1.75

B 0.012 0.016 0.020 0.31 0.41 0.51

C 0.004 0.006 0.01 0.10 0.15 0.25

D 0.186 0.194 0.202 4.72 4.92 5.12

E 0.148 0.156 0.164 3.75 3.95 4.15

e 0.050 BSC 1.27 BSC

H 0.224 0.236 0.248 5.70 6.00 6.30

L 0.012 0.020 0.028 0.30 0.50 0.70

a 0° 5° 8° 0° 5° 8°

Note: Controlling dimensions are millimeters

SOIC - 0.074 grams unit weight

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 7 of 9

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

Mechanical Package Outline 8-Pin TSSOP

Dimensions in inches Dimensions in millimeters

Symbol Min Nor Max Min Nor Max

0.047

1.10

A1 0.002 0.006 0.05 0.15

A2 0.031 0.039 0.041 0.80 1.00 1.05

B 0.007 0.012 0.19 0.30

C 0.004 0.008 0.09 0.20

D 0.114 0.118 0.122 2.90 3.00 3.10

E 0.169 0.173 0.177 4.30 4.40 4.50

e 0.026 BSC 0.65 BSC

H 0.244 0.252 0.260 6.20 6.40 6.60

L 0.018 0.024 0.030 0.45 0.60 0.75

a 0°

5° 8° 0°

5° 8°

Note: Controlling dimensions are millimeters

TSSOP -0.034 grams unit weight

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 8 of 9

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

Ordering Codes

Ordering

Number Marking Package Type QTY / Reel Temperature

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

X278XB-08TT X278XB 8 PIN TSSOP, TUBE See flow

X278XB-08TR X278XB 8 PIN TSSOP, TAPE & REEL 2,500 See flow

Device Ordering Information

X278XX X- 08 XX

Package:

ST – SOIC, TUBE

SR - SOIC, T/R

TT – TSSOP, TUBE

TR - TSSOP, T/R

F = Pb FREE

DEVICE NUMBER

Flow:

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

I = Industrial Temperature Range (-25°C to 85°C)

A = Automotive Tem

erature Ran

(

-40°C to 125°C

)

Pin Count

October 2003 P2781/82/84

rev 1.0

General Purpose EMI Reduction IC 9 of 9

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

2595, Augustine Drive,

Santa Clara, CA 95054

Tel# 408-855-4900

Fax: 408-855-4999

www.alsc.com

Part Number: P2781/82/84

Document Version: 1.0