August 2004 ASM3P2579A
rev 2.0
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.
Low Power Peak EMI Reducing Solution
Features
Generates an EMI optimized clocking signal at the
output.
Integrated loop filter components.
Operates with a 3.3V ±0.3V supply.
Operating current less than 6mA.
Low power CMOS design.
Input frequency range: 15MHz to 40MHz.
Generates a 1X low EMI spread spectrum clock of
the input frequency.
Spread Spectrum Enable Control.
Frequency deviation: ±1%.
Available in 6-pin TSOT-23, 8-pin SOIC and 8-pin
TSSOP packages.
Product Description
The ASM3P2579A is a versatile spread spectrum
frequency modulator designed specifically for a wide
range of clock frequencies. The ASM3P2579A reduces
electromagnetic interference (EMI) at the clock source,
allowing system wide reduction of EMI of all clock
dependent signals. The ASM3P2579A allows significant
system cost savings by reducing the number of circuit
board layers ferrite beads, shielding that are traditionally
required to pass EMI regulations.
The ASM3P2579A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all digital method.
The ASM3P2579A 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 ASM3P2579A is targeted towards all portable
devices with very low power requirements like MP3
players and digital still cameras.
Key Specifications
Description Specification
Supply voltages VDD = 3.3V ±0.3V
Frequency Range 15MHz < CLKIN < 40MHz
Cycle-to-Cycle Jitter 300 ps (maximum)
Output Duty Cycle 40/60% (worst case)
Output Rise and Fall Time 1.1 ns (maximum)
Modulation Rate Equation FIN/640
Frequency Deviation ±1%
Block Diagram
XIN
ModOUT
VSS
Frequency
Divider
Feedback
Divider
Modulation
Phase
Detector
Loop
Filter
VCO Output
Divider
PLL
VDD
Crystal
Oscillator
XOUT
SSON
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XOUT
1
2
34
5
6
ASM3P2579A
SSON
XIN/CLKIN VDD
ModOUT
VSS
Pin Configuration (6-pin TSOT-23)
Pin Description
Pin# Pin Name Type Description
1SSON IWhen SSON is high, it turns on the spread spectrum feature and when low, it turns off
the spread spectrum feature. When Spread Spectrum feature is not required, connect
the pin to ground.
2XOUT OCrystal connection. If using an external reference, this pin must be left unconnected.
3XIN/CLKIN ICrystal connection or external reference frequency input. This pin has dual functions. It
can be connected either to an external crystal or an external reference clock.
4VDD PPower supply for the entire chip (3.3V)
5ModOUT OSpread spectrum clock output.
6VSS PGround connection.
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XIN/CLKIN
VSS
ModOUT
NC
XOUT
1
2
3
45
6
7
8
ASM3P2579A
SSON
NC
VDD
Pin Configuration (8-pin SOIC and TSSOP)
Pin Description
Pin# Pin Name Type Description
1XIN/CLKIN ICrystal connection or external reference frequency input. This pin has dual functions. It
can be connected either to an external crystal or an external reference clock.
2XOUT OCrystal connection. If using an external reference, this pin must be left unconnected.
3 I When SSON is high, it turns on the spread spectrum feature and when low, it turns off
the spread spectrum feature. When Spread Spectrum feature is not required, connect
the pin to ground.
4 NC - No connect.
5VSS PGround connection.
6ModOUT OSpread spectrum clock output.
7 NC - No connect.
8VDD PPower supply for the entire chip (3.3V)
Modulation Profile
Specification
Description Specification
Frequency Range 15MHz < CLKIN < 40MHz
Modulation Equation FIN/640
Frequency Deviation ±1%
SSON
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Absolute Maximum Ratings
Symbol Parameter Rating Unit
VDD, VIN Voltage on any pin with respect to Ground 0.5 to +7.0 V
TSTG Storage temperature -65 to +125 °C
TAOperating temperature 0 to 70 °C
Note: These are stress ratings only and are not implied for functional use. Exposure to absolute maximum ratings
for prolonged periods of time may affect device reliability.
DC Electrical Characteristics
(Test condition: All parameters are measured at room temperature (25°C) unless otherwise stated)
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 – – -35 µA
IIH Input high current – – 35 µA
IXOL XOUT output low current (@4.0V, VDD=3.3V) - 3 - mA
IXOH XOUT output high current (@2.5V, VDD=3.3V) - 3 - 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* – – 1.5 mA
IPD Power-down current** – – 1.0 µA
ICC Dynamic supply current (3.3V, 40MHz and 15pF
loading) – – 6 mA
VDD Operating voltage 3.0 3.3 3.6 V
tON Power-up time (first locked cycle after power-up)*** – – 10 mS
ZOUT Clock output impedance – 50 – ù
*XIN/CLKIN pin is pulled low
**PD pin is pulled low
***VDD and XIN/CLKIN input are stable, PD pin is made high from low.
AC Electrical Characteristics
Symbol Parameter Min Typ Max Unit
CLKIN Input frequency 15 - 40 MHz
ModOUT Output frequency 15 - 40 MHz
tLH* Output rise time (measured at 0.8V to 2.0V) 0.5 0.7 1.1 ns
tHL*Output fall time (measured at 2.0V to 0.8V) 0.5 0.7 1.0 ns
tJC Jitter (cycle to cycle) - - 360 ps
tDOutput duty cycle 45 50 55 %
*tLH and tHL are measured into a capacitive load of 15pF
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Package Information
6-pin TSOT-23
BC
b
D
A1
A2 A
e
L
H
Dimensions in millimeters Dimensions in inches
Symbol
Min Max Min Max
A-1.00 -0.040
A1 0 0.10 00.004
A2 0.87 REF 0.034 REF
B1.40 1.80 0.055 0.071
b0.30 0.50 0.012 0.019
C2.50 3.00 0.0980.118
D2.70 3.10 0.106 0.122
e0.95 BSC 0.037 BSC
H0.10 0.35 0.004 0.014
LMIN 0.20 MIN 0.008
0° 8° 0° 8°
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D
EH
D
A1
A2 A
L
C
B
e
8-Pin SOIC
Symbol Dimensions in inches Dimensions in millimeters
Min Max Min Max
A0.057 0.071 1.45 1.80
A1 0.004 0.010 0.10 0.25
A2 0.053 0.069 1.35 1.75
B0.012 0.020 0.31 0.51
C0.004 0.01 0.10 0.25
D0.186 0.202 4.72 5.12
E0.148 0.164 3.75 4.15
e0.050 BSC 1.27 BSC
H0.224 0.248 5.70 6.30
L0.012 0.028 0.30 0.70
θ0° 8° 0° 8°
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E
H
A
A1
A2
D
B
C
L
e
8-Pin TSSOP
Dimensions in inches Dimensions in millimeters
Symbol Min Max Min Max
A0.047 1.10
A1 0.002 0.006 0.05 0.15
A2 0.031 0.041 0.80 1.05
B0.007 0.012 0.19 0.30
C0.004 0.008 0.09 0.20
D0.114 0.122 2.90 3.10
E0.169 0.177 4.30 4.50
e0.026 BSC 0.65 BSC
H0.244 0.260 6.20 6.60
L0.018 0.030 0.45 0.75
θ0° 8° 0° 8°
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Ordering Information
Part Number Marking Package Type Temperature
ASM3P2579AF-06OR A4LL 6-Pin TSOT-23, TAPE & REEL 0°C –70øC
ASM3P2579AF-08TT ASM3P2579AFT 8-Pin TSSOP, TUBE 0øC –70øC
ASM3P2579AF-08TR ASM3P2579AFT 8-Pin TSSOP, TAPE & REEL 0øC –70øC
ASM3P2579AF-08ST ASM3P2579AFS 8-Pin SOIC, TUBE 0øC –70øC
ASM3P2579AF-08SR ASM3P2579AFS 8-Pin SOIC, TAPE & REEL 0øC –70øC
ASM3P2579A-06OR A1LL 6-Pin TSOT-23, TAPE & REEL 0øC –70øC
ASM3P2579A-08TT ASM3P2579AT 8-Pin TSSOP, TUBE 0øC –70øC
ASM3P2579A-08TR ASM3P2579AT 8-Pin TSSOP, TAPE & REEL 0øC –70øC
ASM3P2579A-08ST ASM3P2579AS 8-Pin SOIC, TUBE 0øC –70øC
ASM3P2579A-08SR ASM3P2579AS 8-Pin SOIC, TAPE & REEL 0øC –70øC
Device Ordering Information
A S M 3 P 2 5 7 9 A F - 0 8 T R
Licensed under U.S Patent Nos 5,488,627 and 5,631,921
OR - SOT23/T/R SR - SOIC, T/R
TT –TSSOP, TUBE QR – QFN, T/R
TR - TSSOP, T/R QT - QFN, TUBE
VT – TVSOP, TUBE BT - BGA, TUBE
VR – TVSOP, T/R BR – BGA, T/R
ST – SOIC, TUBE
PIN COUNT
X = Automotive I = Industrial P or n/c = Commercial
1 – reserved 6 – power management
2 - Non PLL based 7 – power management
3 – EMI Reduction 8 – power management
4 – DDR support products 9 – Hi performance
5
–
STD Zero Delay Buffer
0
-
reserved
Alliance Semiconductor Mixed Signal Product
PART NUMBER
LEAD FREE PART
August 2004 ASM3P2579A
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Note: This product utilizes US Patent # 6,646,463 Impedance Emulator Patent issued to Alliance Semiconductor, dated 11-11-2003
© Copyright 2003 Alliance Semiconductor Corporation. All rights reserved. Our three-point logo, our name and Intelliwatt are
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Alliance Semiconductor Corporation
2595, Augustine Drive,
Santa Clara, CA 95054
Tel# 408-855-4900
Fax: 408-855-4999
www.alsc.com
Copyright ÿ Alliance Semiconductor
All Rights Reserved
Preliminary Information
Part Number: ASM3P2579A
Document Version: v 2.0 8_30_2004