Alliance Semiconductor P1818, P1819, P1820, P1821, P1822 Service Manual
查询I1818A-08SR供应商
Production
March 2003
Features
®
Low Power Mobile VGA EMI Reduction IC
P1818/19/20/21/22
• FCC approved method of EMI attenuation
• Provides up to 15 dB EMI reduction
• Generates a low EMI spread spectrum clock and a
non-spread reference clock of the input frequency
• Optimized for frequency range from 10 MHz to 160
MHz
P1818: 10 to 20 MHz
P1819: 20 to 40 MHz
P1820: 40 to 80 MHz
P1821: 10 to 40 MHz
P1822: 80 to 160 MHz
• Internal loop filter minimizes external components
and board space
Product Description
The P18xx is a versatile spread spectrum frequency
modulator designed specifically for a wide range of input
clock frequencies from 10 to 160 MHz (see Input Frequency and Modulation Rate Selections). The P18xx
can generate an EMI reduced clock from crystal,
ceramic resonator, or system clock. The P18xx-A to
P18xx-H offer various combinations of spread options
and percentage deviations (see Spread Deviation Selections). These combinations include Down Spread,
Center Spread and percentage deviation range from
±0.625% to -3.50%.
The P18xx reduces electromagnetic interference (EMI)
at the clock source, allowing a system wide EMI
reduction for all the down stream clocks and data
dependent signals. The P18xx 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.
• Selectable spread options: Down Spread and Center Spread
• Low inherent cycle-to-cycle jitter
• Eight spread % selections: +/-0.625% to –3.5%
• 3.3V operating voltage
• CMOS/TTL compatible inputs and outputs
• Low power CMOS design
• Supports notebook VGA and other LCD timing
controller applications
• Power down function for mobile application
• Products are available for industrial temperature
range.
• Available in 8-pin SOIC and TSSOP
The P18xx modulates the output of a single PLL in
order to “spread” the bandwidth of a synthesized clock,
thereby decreasing 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 clock generators.
Lowering EMI by increasing a signal’s bandwidth is
called “spread spectrum clock generation”.
The P18xx uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all-digital method.
Applications
The P18xx is targeted toward 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.
Alliance Semiconductor
2575 Augustine Drive • Santa Clara, CA 95054 • Tel: 408.855.4900 • Fax: 408.855.4999 • www.alsc.com
Notice: The information in this document is subject to change without notice.
Pin Diagrams
®
P1818/19/20/21/22
1 8
XIN
VSS
SRS
ModOut
2 7
3
4
XIN
VSS
D_C
ModOut
Block Diagram
P 1 8 1 8 A /B /C /D
P 1 8 1 9 A /B /C /D
P 1 8 2 0 A /B /C /D
1 8
2 7
3
P 1 8 1 8 E /F /G /H
4
P 1 8 1 9 E /F /G /H
P 1 8 2 0 E /F /G /H
6
5
6
5
XOUT
VDD
PD#
REF
XOUT
VDD
PD#
REF
VSS
SRS
ModOut
VSS
SRS
ModOut
1 8
XIN
2 7
3
4
P 1 8 2 1 A /B /C /D
1 8
XIN
2 7
3
4
P1822A
6
5
6
5
XOUT
VDD
FRS
REF
MRS
VDD
SSON#
SR0
XIN
XOUT
Crystal
Oscill a t o r
REF
Frequency
Divider
Feedback
Divider
D_C PD# MRS FRS SRS
Modulation
Phase
Detector
P1818/19/20/21/22 Block Diagram
Loop
Filter
VDD
VSS
PLL
VCO
Output
Divider
ModOUT
Low Power Mobile VGA EMI Reduction IC
Notice: The information in this document is subject to change without notice.
2 of 8March 2003
Input Frequency and Modulation Rate
®
P1818/19/20/21/22
Part number
P1818 10 MHz to 20 MHz 10 MHz to 20 MHz Input frequency / 256
P1819 20 MHz to 40 MHz 20 MHz to 40 MHz Input frequency / 512
P1820 40 MHz to 80 MHz 40 MHz to 80 MHz Input frequency / 2048
FRS=0 10 MHz to 20 MHz 10 MHz to 20 MHz Input frequency / 256
P1821
FRS=1 20 MHz to 40 MHz 20 MHz to 40 MHz Input frequency / 512
P1822 80 MHz to 160 MHz 80 MHz to 160 MHz Input frequency / 3584
Spread Deviation Selections
Part number
2
P1818
/19/20/21A
P1818/19/20/21B 0 N/A N/A -1.25% (Down)
P1818/19/20/21C 0 N/A N/A +/-1.25% (Center)
P1818/19/20/21D 0 N/A N/A +/-0.625% (Center)
P1818/19/20E N/A N/A 0 -1.25% (Down)
P1818/19/20F N/A N/A 0 -2.5% (Down)
P1818/19/20G N/A N/A 0 -1.75% (Down)
2
P1818
P1822A
P1822B
1.A through H represents various combinations of spread deviations, options, and modulation rates.
2. Refer to Frequency vs. Deviation (P1818A and P1818H).
1
/19/20H
Input
frequency range
Output
frequency range
Modulation rate
SRS SR0 D_C Spread deviation
0 N/A N/A -2.50% (Down)
1 -3.50% (Down)
1 -1.75% (Down)
1 +/-1.75% (Center)
1 +/-0.875% (Center)
1 +/-0.625% (Center)
1 +/-1.25% (Center)
1 +/-0.875% (Center)
N/A N/A 0 -3.5% (Down)
1 +/-1.75% (Center)
0 0 N/A -1.25% (Down)
0 1 -2.50% (Down)
1 0 -1.75% (Down)
1 1 -3.50% (Down)
0 0 N/A +/-0.625% (Center)
0 1 +/-1.25% (Center)
1 0 +/-0.875% (Center)
1 1 +/-1.75% (Center)
Low Power Mobile VGA EMI Reduction IC
Notice: The information in this document is subject to change without notice.
3 of 8March 2003
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