November 2003
rev 1.0
P2560B
Features
FCC approved method of EMI attenuation
Generates a low EMI spread spectrum and a non-
spread reference signal of
frequency
Optimized for input frequency range from 20 to 32
MHz
Internal loop filter minimizes external components
and board space
Two selectable spread ranges
Low inherent cycle-to-cycle jitter
3.3 V or 5 V operating voltage
CMOS/TTL compatible inputs and outputs
Ultra low power CMOS design: 5.50 mA @3.3 V
Supports notebook VGA and other LCD timing
controller applications
SSON pin for Spread Spectrum On/Off and
Standby Mode controls
Available in 8-pin SOIC and TSSOP
the input
clock
(EMI) at the clock source allowing system-wide reduction
of EMI of downstream clock and data dependent signals.
It allows significant system cost savings by reducing the
number of circuit board layers and shielding traditionally
required to pass EMI regulations.
The P2560B 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 P2560B uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all-digital method.
Applications
Product Description
The P2560B is a versatile spread spectrum frequency
modulator designed specifically for a wide range of clock
frequencies. It reduces electromagnetic interference
The P2560B is targeted toward the notebook VGA chip
and other displays using an LVDS interface, PC
peripheral devices, and embedded systems
Block Diagram
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.
November 2003
rev 1.0
Pin Configuration
P2560B
P2560B
Standby Mode Selection
CLKIN
Disabled
Disabled
Enabled
Enabled
SSON/SBM
0
1
0
1
Spread Spectrum
N/A
N/A
Off
On
ModOUT
Disabled
Disabled
Reference
Normal
PLL
Disabled
Free
running
Disabled
Normal
Mode
Standby
Free running
Buffer out
Normal
Spread Range Selection, VDD = 3.3 V
CLKIN frequency
20 MHz
25 MHz
27 MHz
30 MHz
32 MHz
Pin Description
Pin# Pin Name
1
2
3
4
5
6
7
8
XIN/CLK
XOUT
DIV2
VSS
SR0
SSON#
MODOUT
VDD
Spreading range
±1.16%
±1.13%
±1.11%
±1.0%
±1.0%
(CLKIN/10) * 20.83 kHz
Modulation rate
Type
I
O
I
P
I
I
O
P
Description
Crystal connection or external reference frequency input. This pin has dual
functions. It can be connected to either an external crystal or an external
reference clock.
Crystal connection. If using an external reference, this pin must be left
unconnected.
Digital logic input used to select normal output mode or divide-by-2 output mode.
When this pin is HIGH, the frequency of the output clock is the same as the input
clock frequency. When it is tied LOW, the output frequency is half the input clock
frequency. This pin has an internal pull-up resistor.
Ground to entire chip.
Digital logic input used to select Spreading Range (Refer Spread Deviation
Table). This pin has an internal pull-up resistor.
Digital logic input used to enable Spread Spectrum function (Active LOW).
Spread Spectrum function enabled when LOW, disabled when HIGH. This pin
has an internal pull-low resistor.
Spread spectrum low EMI output.
Power supply for the entire chip (5V).
Low Frequency EMI Reduction
Notice: The information in this document is subject to change without notice.
2 of 7
November 2003
rev 1.0
Schematic for Notebook VGA Application
P2560B
P2560B
Low Frequency EMI Reduction
Notice: The information in this document is subject to change without notice.
3 of 7
November 2003
rev 1.0
Absolute Maximum Ratings
Symbol
Parameter
V
DD
, V
IN
Voltage on any pin with respect to GND
T
STG
T
A
Storage temperature
Operating temperature
P2560B
Rating
-0.5 to +7.0
-65 to +125
0 to +70
Unit
V
°C
°C
DC Electrical Characteristics
Symbol
Parameter
V
IL
V
IH
I
IL
I
IH
I
XOL
I
XOH
V
OL
V
OH
I
DD
I
CC
V
DD
t
ON
Z
OUT
Input low voltage
Input high voltage
Input low current (pull-up resistor on inputs SR0 and
SSON/SBM)
Input high current
XOUT output low
current
XOUT output high
current
Output low voltage
Output high voltage
at 0.4 V, V
DD
= 3.3V
at 0.4 V, V
DD
= 5.0 V
at 2.5 V, V
DD
= 3.3 V
at 4.5 V, V
DD
= 5.0 V
V
DD
= 3.3 V, I
OL
= 20 mA
V
DD
= 5.0 V, I
OL
= 20 mA
V
DD
= 3.3 V, I
OL
= 20 mA
V
DD
= 5.0 V, I
OL
= 20 mA
Normal mode:
Dynamic supply current
Operating voltage
Power-up time (first locked cycle after power up)
Clock output impedance
3.3 V and 10 pF loading
5.0 V and 10 pF loading
Min
GND - 0.3
2.0
–
–
–
–
–
–
–
–
2.5
4.5
–
fIN-min
3.2
6.2
2.7
–
–
Typ
–
–
–
–
3
20
3
20
–
–
–
–
0.6
fIN-typ
–
–
3.3
0.18
50
Max
0.8
VDD + 0.3
-35
35
–
–
–
–
0.4
–
–
–
–
fIN-max
7.0
13.6
5.5
–
–
Unit
V
V
µA
µA
mA
mA
mA
mA
V
V
V
V
mA
mA
mA
V
mS
Ω
Static supply current standby mode
AC Electrical Characteristics
Symbol
f
IN
f
OUT
t
LH
1
t
HL
1
t
JC
t
D
Input frequency
Output frequency
Output rise time
Output fall time
Jitter (cycle to cycle)
Output duty cycle
Parameter
Min
20
20
Typ
–
–
0.9
0.75
0.8
0.75
–
50
Max
32
32
1.1
–
1.0
–
360
55
Unit
MHz
MHz
ns
ns
ns
ns
ps
%
Measured at 0.8 V to 2.0 V
Measured at 1.2 V to 3.75 V
Measured at 2.0 V to 0.8 V
Measured at 1.2 V to 3.75 V
0.7
–
0.6
–
–
45
Low Frequency EMI Reduction
Notice: The information in this document is subject to change without notice.
4 of 7
November 2003
rev 1.0
Package Information
8-Pin SOIC
SYMBOL
MIN
A
0.057
0.004
0.053
0.012
0.004
0.186
0.148
0.050
0.224
0.012
0°
INCHES
NOR
0.064
0.007
0.061
0.016
0.006
0.194
0.156
BSC
0.236
0.020
5°
MAX
0.071
0.010
0.069
0.020
0.010
0.202
0.164
1.27
0.248
0.028
8°
MIN
1.45
0.10
1.35
0.31
0.10
4.72
3.75
BSC
5.70
0.30
0°
P2560B
MILLIMETERS
NOR
1.63
0.18
1.55
0.41
0.15
4.92
3.95
MAX
1.80
0.25
1.75
0.51
0.25
5.12
4.15
P2560B
A1
A2
B
C
D
E
e
H
L
a
6.00
0.50
5°
6.30
0.70
8°
Note: Controlling dimensions are millimeters.
SOIC - 0.074 grams unit weight
8-Pin TSSOP
SYMBOL
MIN
A
A1
A2
B
C
D
E
e
H
L
a
–
0.002
0.031
0.007
0.004
0.114
0.169
0.026
0.244
0.018
0°
INCHES
NOR
–
–
0.039
–
–
0.118
0.173
BSC
0.252
0.024
–
MAX
0.047
0.006
0.041
0.012
0.008
0.122
0.177
0.65
0.260
0.030
8°
MIN
–
0.05
0.80
0.19
0.09
2.90
4.30
BSC
6.20
0.45
0°
6.40
0.60
–
6.60
0.75
8°
MILLIMETERS
NOR
–
–
1.00
–
–
3.00
4.40
MAX
1.10
0.15
1.05
0.30
0.20
3.10
4.50
Note: Controlling dimensions are millimeters.
TSSOP - 0.034 grams unit weight
Low Frequency EMI Reduction
Notice: The information in this document is subject to change without notice.
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