allows significant system cost savings by reducing the
number of circuit board layers, ferrite beads, shielding, and
other passive components that are traditionally required to
pass EMI regulations.
The ASM3P18S19B 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’.
The ASM3P18S19B uses the most efficient and optimized
modulation
profile
approved
by
the
FCC
and
is
implemented in a proprietary all digital method.
FCC approved method of EMI attenuation.
Provides up to 15dB EMI reduction.
Generates a low EMI Spread Spectrum clock and a
non-spread reference clock of the input frequency.
Optimized for Frequency range from 20 to 40MHz.
Internal loop filter minimizes external components and
board space.
Low Inherent Cycle-to-Cycle jitter.
Two spread % selections: -1.25% to -1.75%.
3.3V Operating Voltage.
Low power CMOS design.
Supports notebook VGA and other LCD timing
controller applications.
Power Down function for mobile application.
Available in Commercial temperature range.
Available in 8-pin SOIC and TSSOP Packages.
RoHS Compliant
Applications
The ASM3P18S19B is targeted towards EMI management
for memory and LVDS interfaces in mobile graphic chipsets
and high-speed digital applications such as PC peripheral
devices, consumer electronics, and embedded controller
systems.
Product Description
The ASM3P18S19B is a Versatile Spread Spectrum
Frequency Modulator designed specifically for input clock
frequencies from 20 to 40MHz. (Refer
Input Frequency and
Modulation Rate Table).
The ASM3P18S19B reduces
electromagnetic interference (EMI) at the clock source,
allowing system wide reduction of EMI of
down stream
clock and data dependent signals. The ASM3P18S19B
Block Diagram
PD#
SRS
VDD
Modulation
XIN/CLKIN
Crystal
Oscillator
Frequency
Divider
Feedback
Divider
PLL
XOUT
Phase
Detector
Loop
Filter
VCO
Output
Divider
REF
ModOUT
VSS
PulseCore Semiconductor Corporation
1715 S. Bascom Ave Suite 200, Campbell, CA 95008
•
Tel: 408-879-9077
•
Fax: 408-879-9018
www.pulsecoresemi.com
Notice: The information in this document is subject to change without notice.
November 2006
rev 2.2
Pin Configuration
XIN/ CLKIN
VSS
SRS
ModOUT
1
2
3
4
8
7
6
5
XOUT
VDD
PD#
REF
ASM3P18S19B
ASM3P18S19B
Pin Description
Pin#
1
2
3
4
5
6
7
8
Pin Name
XIN / CLKIN
VSS
SRS
ModOUT
REF
PD#
VDD
XOUT
Type
I
P
I
O
O
I
P
O
Description
Crystal Connection or external frequency input.This pin has dual
functions. It can be connected to either an external crystal or an external
reference clock
Ground Connection. Connect to system ground.
Spread range select. Digital logic input used to select frequency deviation
(Refer Spread Deviation Selection Table).
This pin has an internal pull-up
resistor.
Spread spectrum clock output.
(Refer Input Frequency and Modulation
Rate Table and Spread Deviation Selection Table)
Non-modulated Reference clock output of the input frequency.
Power down control pin. Pull LOW to enable Power-Down mode. This pin
has an internal pull-up resistor.
Power Supply for the entire chip.
Crystal Connection. Input connection for an external crystal. If using an
external reference, this pin must be left unconnected.
Input Frequency and Modulation Rate
Part Number
ASM3P18S19B
Input Frequency Range
20MHz to 40MHz
Output Frequency range
20MHz to 40MHz
Modulation rate
Input Frequency / 512
Spread Deviation Selection
Part Number
ASM3P18S19B
SRS
0
1
Spread Deviation
-1.25% (DOWN)
-1.75% (DOWN)
Low Power Mobile VGA EMI Reduction IC
Notice: The information in this document is subject to change without notice.
2 of 7
November 2006
rev 2.2
Absolute Maximum Ratings
Symbol
VDD, V
IN
T
STG
T
A
T
s
T
J
T
DV
Storage temperature
Operating temperature
Max. Soldering Temperature (10 sec)
Junction Temperature
Static Discharge Voltage (As per JEDEC STD22- A114-B)
ASM3P18S19B
Parameter
Rating
-0.5 to +4.6
-65 to +125
0 to +70
260
150
2
Unit
V
°C
°C
°C
°C
KV
Voltage on any pin with respect to Ground
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
V
IL
V
IH
I
IL
I
IH
I
XOL
I
XOH
V
OL
V
OH
I
CC
I
DD
VDD
t
ON
Z
OUT
Input Low voltage
Input High voltage
Parameter
Min
VSS - 0.3
2.0
-60.0
-
-
-
-
2.5
7.1
f
IN - min
-
-
-
-
Typ
-
-
-
-
3
3
-
-
-
4.5
3.3
0.18
50
Max
0.8
VDD + 0.3
-20.0
1.0
-
-
0.4
-
26.9
f
IN - max
-
-
-
-
Unit
V
V
µA
µA
mA
mA
V
V
mA
mA
V
mS
Ω
Input Low current (inputs PD#, SRS)
Input High current
X
OUT
Output low current @ 0.4V, VDD = 3.3V
X
OUT
Output high current @ 2.5V, VDD = 3.3V
Output Low voltage VDD = 3.3V, I
OL
= 20mA
Output High voltage VDD = 3.3V, I
OH
= 20mA
Dynamic supply current normal mode
3.3V and 25pF probe loading
Static supply current standby mode
Operating Voltage
Power up time (first locked clock cycle after power up)
Clock Output impedance
AC Electrical Characteristics
Symbol
Parameter
f
IN
f
OUT
t
LH
*
t
HL
*
t
JC
t
D
Input Frequency
Output Frequency
Output Rise time
Measured from 0.8V to 2.0V
Output Fall time
Measured from 0.8V to 2.0V
Jitter (Cycle to cycle)
Output Duty cycle
Min
20
20
-
-
-200
45
Typ
-
-
0.66
0.65
-
50
Max
40
40
-
-
200
55
Unit
MHz
MHz
nS
nS
pS
%
*t
LH
and t
HL
are measured into a capacitive load of 15pF
Low Power Mobile VGA EMI Reduction IC
Notice: The information in this document is subject to change without notice.
3 of 7
November 2006
rev 2.2
Package Information
8-lead (150-mil) SOIC Package
ASM3P18S19B
Dimensions
Symbol
Min
A1
A
A2
B
C
D
E
e
H
L
θ
0.004
0.053
0.049
0.012
0.007
Inches
Max
0.010
0.069
0.059
0.020
0.010
Millimeters
Min
Max
0.10
1.35
1.25
0.31
0.18
4.90 BSC
3.91 BSC
1.27 BSC
6.00 BSC
0.41
0°
1.27
8°
0.25
1.75
1.50
0.51
0.25
0.193 BSC
0.154 BSC
0.050 BSC
0.236 BSC
0.016
0°
0.050
8°
Package length (Excluding end flash)D - 188 ~ 193 mils.
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