Standard Peak EMI Reducing Solution

ASM3P2474A
Peak EMI
Reducing Solution
The ASM3P2474A 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.
•
Operates with a 3.3V Supply.
•
Operating current less than 6mA.
•
CMOS design.
•
Input frequency range : 13MHz to 30MHz
•
Generates a 1X and 2X low EMI spread
The ASM3P2474A 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.’
spectrum clock of the input frequency.
•
Output Frequency Selection through FSEL pin
•
Frequency deviation : -1.5% (Typ) @25MHz
Applications
-1.5% (Typ) @50MHz
•
The ASM3P2474A is targeted towards all portable
devices like MP3 players and digital still cameras.
Available in 6L-TSOP (6L-TSOT-23) package.
Product Description
The ASM3P2474A is a versatile spread spectrum
frequency modulator designed specifically for a wide
range of clock frequencies. The ASM3P2474A reduces
electromagnetic interference (EMI) at the clock source,
allowing system wide reduction of EMI of all clock
dependent signals. The ASM3P2474A 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.
Key Specifications
Description
Specification
Supply voltages
VDD = 3.3V ± 0.3V
Cycle-to-Cycle Jitter
±200pS (Typ)
Output Duty Cycle
45/55% (worst case)
Modulation Rate Equation
FIN/640
Frequency
Deviation
FSEL=0
-1.5% (Typ) @ 50MHz
FSEL=1
-1.5% (Typ) @ 25MHz
Block Diagram
FSEL
VDD
PLL
Modulation
XIN / CLKIN
XOUT
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:
ASM3P2474/D
ASM3P2474A
Pin Configuration (6L-TSOP Package)
FSEL 1
XOUT
2
6 VSS
ASM3P2474A
XIN / CLKIN 3
5
ModOUT
4
VDD
Pin Description
Pin#
Pin Name
Type
Description
1
FSEL
I
Selection Pin for 1X and 2X Output Frequency Options. Please refer to the table
Frequency Selection Options for further details.
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.
Modulation Profile
Specifications
Description
Specification
Frequency Range
13MHz < CLKIN < 30MHz
Modulation Equation
FIN/640
Frequency Deviation
FSEL=0
-1.5% (Typ) @ 50MHz
FSEL=1
-1.5% (Typ) @ 25MHz
Frequency Selection Options
FSEL Pin
0
Input Frequency (MHz)
13-30
Output Frequency (MHz)
26-60
1
13-30
13-30
Rev. 2 | Page 2 of 7 | www.onsemi.com
ASM3P2474A
Absolute Maximum Ratings
Symbol
Parameter
Rating
Unit
VDD, VIN
Voltage on any pin with respect to Ground
-0.5 to +4.6
V
Storage temperature
-65 to +125
°C
TSTG
Ts
Max. Soldering Temperature (10 sec)
260
°C
TJ
Junction Temperature
150
°C
2
KV
Static Discharge Voltage
TDV
(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
Description
Min
Max
Unit
Supply Voltage
3
3.6
V
0
TA
Operating Temperature (Ambient Temperature)
70
°C
CL
Load Capacitance
15
pF
CIN
Input Capacitance
7
pF
DC Electrical Characteristics
Symbol
Max
Unit
VIL
Input low voltage
Parameter
VSS-0.3
Min
Typ
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 = 3.3V, IOL = 8mA)
VOH
Output high voltage (VDD = 3.3V, IOH = 8mA)
IDD
ICC
VDD
tON
ZOUT
0.4
2.5
1
Static supply current
Dynamic supply current
(3.3V, 25MHz and no load and FSEL=1)
Operating voltage
3.0
V
1.6
mA
4.0
mA
3.3
Power-up time (first locked cycle after power-up)
Output impedance
45
Note: 1. XIN /CLKIN pin is pulled low.
Rev. 2 | Page 3 of 7 | www.onsemi.com
V
3.6
V
5
mS
Ω
ASM3P2474A
AC Electrical Characteristics
Symbol
CLKIN
ModOUT
Parameter
Output frequency
fd
Frequency Deviation
fd
Frequency Deviation
Max
Unit
13
30
MHz
FSEL = 0
26
60
FSEL = 1
13
30
-1.8
Output Frequency = 30MHz
-0.9
Output Frequency = 26MHz
-1.8
Output Frequency = 60MHz
-0.9
Output rise time (measured from 0.8 to 2.0V)
0.4
1
Output fall time (measured at 2.0V to 0.8V)
0.3
tJC
Jitter (cycle-to-cycle)
tD
Output duty cycle
Typ
Output Frequency = 13MHz
1
tLH
tHL
Min
Input frequency
%
%
0.85
1.1
nS
0.7
0.9
nS
±200
45
50
pS
55
Note: 1. tLH and tHL are measured into a capacitive load of 15pF.
Typical Crystal Specifications
Fundamental AT cut parallel resonant crystal
Nominal frequency
25MHz
Frequency tolerance
± 30 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
Crystal
CL
Rx
CL
CL = 2*(CP – CS),
Where CP = Load capacitance of crystal
CS = Stray capacitance due to CIN, PCB, Trace etc.
Rev. 2 | Page 4 of 7 | www.onsemi.com
MHz
%
ASM3P2474A
Typical Application Schematic
VDD
C1
0.1µF
C2
2.2µF
VDD
ASM3P2474A
ModOUT
VSS
Rev. 2 | Page 5 of 7 | www.onsemi.com
Rs
ModOUT Clock
ASM3P2474A
Package Information
6L-TSOP Package
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
ASM3P2474A
Ordering Information
Part Number
ASM3P2474AF-06OR
Marking
Package Type
Temperature
W4L
6L-TSOP (6L-TSOT-23), TAPE & REEL,
Pb Free
0°C to +70°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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