August 2005 ASM3P2579A
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.
Low Power Peak EMI Reducing Solution
Features
Generates an EMI optimized clock signal at the
output.
Integrated loop filter components.
Operates with a 3.3 / 2.5V Supply.
Operating current less than 4mA.
Low power CMOS design.
Input frequency range: 12MHz to 30MHz for 2.5V
: 12MHz to 30MHz for 3.3V
Generates a 1X low EMI spread spectrum clock of
the input frequency.
Spread Spectrum Enable Control.
Frequency deviation: ±1% @ 24MHz
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/2.5V
Cycle-to-Cycle Jitter 200pS (Max)
Output Duty Cycle 45/55% (worst case)
Modulation Rate Equation FIN/640
Frequency Deviation ±1% @ 24MHz
Block Diagram
ModOUT
VSS
XIN
Frequency
Divide
r
Feedback
Divide
r
Modulation
Phase
Detecto
r
Loop
Filte
r
VCO Output
Divide
r
PLL
Crystal
Oscillator
XOUT
SSON
VDD
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Notice: The information in this document is subject to change without notice.
VDD
ModOUT
XIN/CLKIN
XOUT
1
2
3 4
5
6
ASM3P2579A
SSON VSS
Pin Configuration (6-pin TSOT-23 Package)
Pin Description
Pin# Pin Name Type Description
1 SSON I
When SSON is HIGH, the spread spectrum is enabled and when LOW, it turns off the
spread spectrum. Connect the pin to ground When Spread Spectrum feature is not
required.
2 XOUT O Crystal connection. If using an external reference, this pin must be left unconnected.
3 XIN/CLKIN I Crystal 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.
4 VDD P Power supply for the entire chip
5 ModOUT O Spread spectrum clock output.
6 VSS P Ground connection.
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Notice: The information in this document is subject to change without notice.
XIN/CLKIN
VSS
ModOUT
NC
XOUT
1
2
3
4 5
6
7
8
ASM3P2579A
SSON
NC
VDD
Pin Configuration (8-pin SOIC and TSSOP Packages)
Pin Description
Pin# Pin Name Type Description
1 XIN/CLKIN I Crystal 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.
2 XOUT O Crystal connection. If using an external reference, this pin must be left unconnected.
3 I
When SSON is HIGH, the spread spectrum is enabled and when LOW, it turns off the
spread spectrum. Connect the pin to ground When Spread Spectrum feature is not
required.
4 NC - No connect.
5 VSS P Ground connection.
6 ModOUT O Spread spectrum clock output.
7 NC - No connect.
8 VDD P Power supply for the entire chip
Modulation Profile
Specifications
Description Specification
Frequency Range 12MHz < CLKIN < 30MHz
Modulation Equation FIN/640
Frequency Deviation ±1% @ 24MHz
SSON
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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 Ground -0.5 to +7.0 V
TSTG Storage temperature -65 to +125 °C
TA Operating temperature 0 to 70 °C
Ts Max. Soldering Temperature (10 sec) 260 °C
TJ Junction Temperature 150 °C
TDV Static Discharge Voltage
(As per JEDEC STD22- A114-B)
2 KV
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 for 2.5V Supply
(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 - - -35 µA
IIH Input high current - - 35 µA
IXOL XOUT output low current (@0.5V, VDD=2.5V) - 3 - mA
IXOH XOUT output high current (@1.8V, VDD=2.5V) - 3 - mA
VOL Output low voltage (VDD = 2.5 V, IOL = 8mA) - - 0.6 V
VOH Output high voltage (VDD = 2.5 V, IOH = 8mA) 1.8 - - V
IDD Static supply current * - 1.1 - mA
ICC Dynamic supply current (2.5V, 24MHz and no load) - 3.5 - mA
VDD Operating Voltage 2.375 2.5 2.625 V
tON Power-up time (first locked cycle after power-up) - - 5 mS
ZOUT Output impedance - 50 - Ω
* XIN/CLKIN is made low.
AC Electrical Characteristics for 2.5V Supply
Symbol Parameter Min Typ Max Unit
CLKIN Input frequency 12 - 30 MHz
ModOUT Output frequency 12 - 30 MHz
Input Frequency = 12MHz - - ±1.65
fd Frequency Deviation
Input Frequency = 30MHz - - ±0.80
%
tLH* Output rise time (measured from 0.7V to 1.7V) 0.7 1.5 1.9 nS
tHL* Output fall time (measured from 1.7V to 0.7V) 0.4 1.0 1.1 nS
tJC Jitter (cycle to cycle) - - 200 pS
tD Output duty cycle 45 50 55 %
* tLH and tHL are measured into a capacitive load of 15pF
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Notice: The information in this document is subject to change without notice.
DC Electrical Characteristics for 3.3V Supply
(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 - - -35 µA
IIH Input high current - - 35 µA
IXOL XOUT output low current (@0.4V, 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 = 8mA) - - 0.4 V
VOH Output high voltage (VDD = 3.3 V, IOH = 8mA) 2.5 - - V
IDD Static supply current* - 1.2 - mA
ICC Dynamic supply current (3.3V, 24MHz and no load) - 4.0 - mA
VDD Operating Voltage 2.7 3.3 3.6 V
tON Power-up time (first locked cycle after power-up) - - 5 mS
ZOUT Output impedance - 45 - Ω
* XIN/CLKIN is made low.
AC Electrical Characteristics for 3.3V Supply
Symbol Parameter Min Typ Max Unit
CLKIN Input frequency 12 - 30 MHz
ModOUT Output frequency 12 - 30 MHz
Input Frequency = 12MHz - - ±1.65
fd Frequency Deviation
Input Frequency = 30MHz - - ±0.80
%
tLH* Output rise time (measured from 0.8 to 2.0V) 0.5 1.4 1.7 nS
tHL* Output fall time (measured at 2.0V to 0.8V) 0.4 1.0 1.2 nS
tJC Jitter (cycle to cycle) - - 200 pS
tD Output duty cycle 45 50 55 %
*tLH and tHL are measured into a capacitive load of 15pF
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Notice: The information in this document is subject to change without notice.
Typical Crystal Oscillator Circuit
Typical Crystal Specifications
Fundamental AT cut parallel resonant crystal
Nominal frequency 14.31818MHz
Frequency tolerance ± 50 ppm or better at 25°C
Operating temperature range -25°C to +85°C
Storage temperature -40°C to +85°C
Load capacitance 18pF
Shunt capacitance 7pF maximum
ESR 25Ω
R1 = 510Ω
C1 = 27 pF C2 = 27 pF
Crystal
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Notice: The information in this document is subject to change without notice.
Package Information
6-pin TSOT-23 Package
Dimensions
Inches Millimeters
Symbol
Min Max Min Max
A 0.04 1.00
A1 0.00 0.004 0.00 0.10
A2 0.033 0.036 0.84 0.90
b 0.012 0.02 0.30 0.50
H 0.005 BSC 0.127 BSC
D 0.114 BSC 2.90 BSC
B 0.06 BSC 1.60 BSC
e 0.0374 BSC 0.950 BSC
C 0.11 BSC 2.80 BSC
L 0.0118 0.02 0.30 0.50
θ 0° 4° 0° 4°
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Notice: The information in this document is subject to change without notice.
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°
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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
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°
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Notice: The information in this document is subject to change without notice.
Ordering Information
Part Number Marking Package Type Temperature
ASM3P2579AF-06OR S4LL 6-Pin TSOT-23, TAPE & REEL, Pb Free Commercial
ASM3P2579AF-08TT 3P2579AF 8-Pin TSSOP, TUBE, Pb Free Commercial
ASM3P2579AF-08TR 3P2579AF 8-Pin TSSOP, TAPE & REEL, Pb Free Commercial
ASM3P2579AF-08ST 3P2579AF 8-Pin SOIC, TUBE, Pb Free Commercial
ASM3P2579AF-08SR 3P2579AF 8-Pin SOIC, TAPE & REEL, Pb Free Commercial
ASM3P2579A-06OR S1LL 6-Pin TSOT-23, TAPE & REEL Commercial
ASM3P2579A-08TT 3P2579A 8-Pin TSSOP, TUBE Commercial
ASM3P2579A-08TR 3P2579A 8-Pin TSSOP, TAPE & REEL Commercial
ASM3P2579A-08ST 3P2579A 8-Pin SOIC, TUBE Commercial
ASM3P2579A-08SR 3P2579A 8-Pin SOIC, TAPE & REEL Commercial
ASM3P2579AG-06OR S3LL 6-Pin TSOT-23, TAPE & REEL, Green Commercial
ASM3P2579AG-08TT 3P2579AG 8-Pin TSSOP, TUBE, Green Commercial
ASM3P2579AG-08TR 3P2579AG 8-Pin TSSOP, TAPE & REEL, Green Commercial
ASM3P2579AG-08ST 3P2579AG 8-Pin SOIC, TUBE, Green Commercial
ASM3P2579AG-08SR 3P2579AG 8-Pin SOIC, TAPE & REEL, Green Commercial
ASM3I2579AF-06OR S5LL 6-Pin TSOT-23, TAPE & REEL, Pb Free Industrial
ASM3I2579AF-08TT 3I2579AF 8-Pin TSSOP, TUBE, Pb Free Industrial
ASM3I2579AF-08TR 3I2579AF 8-Pin TSSOP, TAPE & REEL, Pb Free Industrial
ASM3I2579AF-08ST 3I2579AF 8-Pin SOIC, TUBE, Pb Free Industrial
ASM3I2579AF-08SR 3I2579AF 8-Pin SOIC, TAPE & REEL, Pb Free Industrial
ASM3I2579A-06OR S2LL 6-Pin TSOT-23, TAPE & REEL Industrial
ASM3I2579A-08TT 3I2579A 8-Pin TSSOP, TUBE Industrial
ASM3I2579A-08TR 3I2579A 8-Pin TSSOP, TAPE & REEL Industrial
ASM3I2579A-08ST 3I2579A 8-Pin SOIC, TUBE Industrial
ASM3I2579A-08SR 3I2579A 8-Pin SOIC, TAPE & REEL Industrial
ASM3I2579AG-06OR S6LL 6-Pin TSOT-23, TAPE & REEL, Green Industrial
ASM3I2579AG-08TT 3I2579AG 8-Pin TSSOP, TUBE, Green Industrial
ASM3I2579AG-08TR 3I2579AG 8-Pin TSSOP, TAPE & REEL, Green Industrial
ASM3I2579AG-08ST 3I2579AG 8-Pin SOIC, TUBE, Green Industrial
ASM3I2579AG-08SR 3I2579AG 8-Pin SOIC, TAPE & REEL, Green Industrial
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Notice: The information in this document is subject to change without notice.
Device Ordering Information
ASM3P2579AF-08TR
Licensed under U.S Patent Nos 5,488,627 and 5,631,921
O = SOT U = MSOP
S = SOIC E = TQFP
T = TSSOP L = LQFP
A = SSOP U = MSOP
V = TVSOP P = PDIP
B = BGA D = QSOP
Q
=
QFN
X
=
SC
-
DEVICE PIN COUNT
X= Automotive I= Industrial P or n/c = Commercial
(-40C to +125C) (-40C to +85C) (0C to +70C)
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 Dela
y
Buffe
r
0 = Reser
v
ed
ALLIANCE SEMICONDUCTOR MIXED SIGNAL PRODUCT
PART NUMBER
F = LEAD FREE AND RoHS COMPLIANT PART
G = GREEN PACKAGE
R = Tape & reel, T = Tube or Tray
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Notice: The information in this document is subject to change without notice.
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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assumes no responsibility for any errors that may appear in this document. The data contained herein represents Alliance's
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without notice. If the product described herein is under development, significant changes to these specifications are possible.
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Alliance Semiconductor Corporation
2575 Augustine Drive,
Santa Clara, CA 95054
Tel# 408-855-4900
Fax: 408-855-4999
www.alsc.com
Copyright © Alliance Semiconductor
All Rights Reserved
Preliminary Information
Part Number: ASM3P2579A
Document Version: v1.0