Standard Peak EMI Reducing Solution

ASM3P2579A
Peak EMI
Reducing Solution
-The ASM3P2579A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all digital method.
Features
• Generates an EMI optimized clock signal at the
output.
• Integrated loop filter components.
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 result 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.’
• Operates with a 3.3 / 2.5V Supply.
• Operating current less than 4mA.
• 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.
Applications
• Frequency deviation: ±1% @ 24MHz
The ASM3P2579A is targeted towards all portable
devices like MP3 players and digital still cameras.
• Available in 6L-TSOP (6L-TSOT-23).
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 and shielding that are
traditionally required to pass EMI regulations.
Block Diagram
Key Specifications
Description
Specification
Supply voltages
VDD = 3.3V/2.5V
Cycle-to-Cycle Jitter
±200pS (Typ)
Output Duty Cycle
45/55% (worst case)
Modulation Rate Equation
FIN/640
Frequency Deviation
±1% @ 24MHz
VDD
SSON
XOUT
PLL
Modulation
XIN
Crystal
Oscillator
Frequency
Divider
Feedback
Divider
Phase
Detector
Loop
Filter
VCO
Output
Divider
ModOUT
VSS
©2010 SCILLC. All rights reserved.
OCTOBER 2010 – Rev. 2.1
Publication Order Number:
ASM3P2579/D
ASM3P2579A
Pin Configuration (6L-TSOP)
SSON
1
XOUT
2
XIN / CLKIN
3
ASM3P2579A
6
VSS
5
ModOUT
4
VDD
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.
Absolute Maximum Ratings
Symbol
VDD, VIN
TSTG
Parameter
Rating
Unit
Voltage on any pin with respect to Ground
-0.5 to +4.6
V
Storage temperature
-65 to +125
°C
Ts
Max. Soldering Temperature (10 sec)
260
°C
TJ
Junction Temperature
150
°C
2
KV
TDV
Static Discharge Voltage
(As per JEDEC STD22- A114-B)
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.
Operating Conditions
Parameter
VDD
TA
Description
Supply Voltage
Operating Temperature (Ambient Temperature)
Min
Max
Unit
2.375
3.6
V
-40
+85
°C
CL
Load Capacitance
15
pF
CIN
Input Capacitance
7
pF
Rev. 2 | Page 2 of 7 | www.onsemi.com
ASM3P2579A
DC Electrical Characteristics for 2.5V Supply
Symbol
Parameter
VIL
Min
Typ
Max
Unit
V
Input low voltage
VSS-0.3
0.8
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 = 2.5V, IOL = 8mA)
VOH
Output high voltage (VDD = 2.5V, IOH = 8mA)
0.6
IDD
Static supply current
1.1
mA
ICC
Dynamic supply current (2.5V, 24MHz and no load)
3.5
mA
1.8
1
VDD
tON
Operating Voltage
2.375
2.5
Power-up time (first locked cycle after power-up)
ZOUT
V
V
Output impedance
2.625
V
5
mS
50
Ω
Note: 1. XIN / CLKIN is made low.
AC Electrical Characteristics for 2.5V Supply
Symbol
CLKIN
ModOUT
fd
Min
Typ
Max
Unit
Input frequency
12
30
MHz
Output frequency
12
30
MHz
Frequency Deviation
Input Frequency = 12MHz
±1.65
Input Frequency = 30MHz
±0.80
%
1
Output rise time (measured from 0.7V to 1.7V)
0.7
1.5
1.9
nS
1
Output fall time (measured from 1.7V to 0.7V)
0.4
1.0
1.1
nS
tLH
tHL
Parameter
tJC
Jitter (cycle-to-cycle)
tD
Output duty cycle
±200
45
Note: 1. tLH and tHL are measured into a capacitive load of 15pF.
Rev. 2 | Page 3 of 7 | www.onsemi.com
50
pS
55
%
ASM3P2579A
DC Electrical Characteristics for 3.3V Supply
Symbol
Parameter
VIL
Min
Typ
Max
Unit
V
Input low voltage
VSS-0.3
0.8
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 = 3.3V, IOL = 8mA)
VOH
Output high voltage (VDD = 3.3V, IOH = 8mA)
0.4
IDD
Static supply current
1.2
mA
ICC
Dynamic supply current (3.3V, 24MHz and no load)
4.0
mA
1
VDD
tON
Operating Voltage
2.7
V
3.3
Power-up time (first locked cycle after power-up)
ZOUT
V
2.5
Output impedance
3.6
V
5
mS
45
Ω
Note: 1. XIN / CLKIN is made low.
AC Electrical Characteristics for 3.3V Supply
Symbol
CLKIN
ModOUT
fd
Min
Typ
Max
Unit
Input frequency
12
30
MHz
Output frequency
12
30
MHz
Frequency Deviation
Input Frequency = 12MHz
±1.65
Input Frequency = 30MHz
±0.80
%
1
Output rise time (measured from 0.8 to 2.0V)
0.5
1.4
1.7
nS
1
Output fall time (measured at 2.0V to 0.8V)
0.4
1.0
1.2
nS
tLH
tHL
Parameter
tJC
Jitter (cycle-to-cycle)
tD
Output duty cycle
±200
45
Note: 1. tLH and tHL are measured into a capacitive load of 15pF.
Rev. 2 | Page 4 of 7 | www.onsemi.com
50
pS
55
%
ASM3P2579A
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(CP)
18pF
Shunt capacitance
7pF maximum
ESR
25 Ω
Note: Note: CL is Load Capacitance and Rx is used to prevent oscillations at overtone frequency of the Fundamental frequency.
Typical Crystal Interface Circuit
R
Rx
Crystal
CL
CL
CL = 2*(CP – CS),
Where CP = Load capacitance of crystal
CS = Stray capacitance due to CIN, PCB, Trace etc.
Typical Application Schematic
VDD
C1
0.1µF
C2
2.2µF
VDD
ASM3P2579A
ModOUT
VSS
Rev. 2 | Page 5 of 7 | www.onsemi.com
Rs
ModOUT Clock
ASM3P2579A
Package Information
6L-TSOP
Dimensions
Symbol
Inches
Min
A
Millimeters
Max
Min
Max
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°
Rev. 2 | Page 6 of 7 | www.onsemi.com
ASM3P2579A
Ordering Information
Part Number
Marking
ASM3I2579AF-06OR
S5L
Package Type
Temperature
6L-TSOP (6L-TSOT-23), TAPE & REEL,
Pb Free
-40°C to +85°C
A “microdot” placed at the end of last row of marking or just below the last row toward the center of package indicates Pb-free.
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