ICS ICS8431-11

ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
GENERAL DESCRIPTION
FEATURES
The ICS8431-11 is a general purpose clock
frequency synthesizer for IA64/32 application and
HiPerClockS™
a member of the HiPerClockS™ family of High
Performance Clock Solutions from ICS. The VCO
operates at a frequency range of 190MHz to
510MHz providing an output frequency range of 95MHz to
255MHz. The output frequency can be programmed using the
parallel interface, M0 thru M8, to the configuration logic.
Spread spectrum clocking is programmed via the control
inputs SSC_CTL0 and SSC_CTL1.
• Fully integrated PLL
,&6
• Differential 3.3V LVPECL output
• Programmable PLL loop divider for generating a variety of
output frequencies.
• Crystal oscillator interface
• Spread Spectrum Clocking (SSC) fixed at 1/2% modulation
for environments requiring ultra low EMI
• Typical RMS cycle-to-cycle jitter 2.6 ps
• LVTTL / LVCMOS control inputs
Programmable features of the ICS8431-11 support four
operational modes. The four modes are spread spectrum
clocking (SSC), non-spread spectrum clock and two test
modes which are controlled by the SSC_CTL[1:0] pins. Unlike other synthesizers, the ICS8431-11 can immediately
change spread-spectrum operation without having to reset
the device.
• PLL bypass modes supporting in-circuit testing and on-chip
functional block characterization
• 3.3V supply voltage
• 28 lead SOIC
• 0°C to 85°C ambient operating temperature
In SSC mode, the output clock is modulated in order to
achieve a reduction in EMI. In one of the PLL bypass test
modes, the PLL is disconnected as the source to the
differential output allowing an external source to be
connnected to the TEST_I/O pin. This is useful for incircuit testing and allows the differential output to be driven
at a lower frequency throughout the system clock tree. In the
other PLL bypass mode, the oscillator divider is used as the
source to both the M and the Fout divide by 2. This is useful
for characterizing the oscillator and internal dividers.
BLOCK DIAGRAM
PIN ASSIGNMENT
XTAL1
OSC
XTAL2
÷ 16
PHASE
DETECTOR
PLL
VCO
÷2
FOUT
nFOUT
÷M
M0
M1
M2
M3
M4
M5
M6
M7
M8
SSC_CTL0
SSC_CTL1
VEE
TEST_I/O
VDD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
nP_LOAD
VDDI
XTAL2
XTAL1
nc
nc
VDDA
VEE
MR
nc
VDDO
FOUT
nFOUT
VEE
ICS8431-11
TEST_I/O
Configuration
Logic
M0:M8
nP_LOAD
ICS8431CM-11
SSC
Control
Logic
28-Lead SOIC
M Package
Top View
SSC_CTL0 SSC_CTL1
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1
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
TABLE 1. PIN DESCRIPTIONS
Number
Name
Type
Description
1-5
M0-M6
Input
Pulldown
6-8
M7-M8
Input
Pullup
10, 11
SSC CTL0,
SSC CTL1
Input
Pullup
12
VEE
Power
Ground pin for core and test output.
13
TEST I/O
Input /
Output
Programmed as input in PLL bypass mode.
14
VDD
Power
Power supply pin for core and test output.
15
VEE
Power
Ground pin for output.
16, 17
nFOUT, FOUT
Output
These differential outputs are main output drivers for the synthesizer.
They are compatible with terminated positive referenced LVPECL
logic.
18
VDDO
Power
Power supply pin for output.
19, 23, 24
nc
Unused
20
MR
Input
21
VEE
Power
Ground pin.
22
VDDA
Power
PLL power supply pin.
25, 26
XTAL1, XTAL2
Input
Cr ystal oscillator input.
27
VDDI
Power
Power supply pin for core.
28
nP_LOAD
Input
M divider inputs. Data latched on LOW-to-HIGH transistion of
nP_LOAD input. LVCMOS / LVTTL pins interface levels.
M divider inputs. Data latched on LOW-to-HIGH transistion of
nP_LOAD input. LVCMOS / LVTTL pins interface levels.
SCC control pins. LVTTL / LVCMOS interface levels.
No connection.
Pulldown Reset M counter. Forces FOUT low.
Pulldown M divider latch enable input. LVTTL / LVCMOS interface levels.
TABLE 2. PIN CHARACTERISTICS
Symbol
Parameter
Test Conditions
Minimum
Typical
Maximum
CIN
Input Pin Capacitance
RPULLUP
Input Pullup Resistor
51
KΩ
RPULLDOWN
Input Pulldown Resistor
51
KΩ
ICS8431CM-11
4
Units
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2
pF
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
TABLE 3A. SSC CONTROL INPUT FUNCTION TABLE
Inputs
Outputs
Operational Modes
FOUT,
SSC_CTL1 SSC_CTL0
TEST_I/O
nFOUT
fXTAL ÷ 16 PLL bypass; Oscillator, oscillator, M and N
0
0
Internal
Disabled fXTAL ÷ 32
÷M
dividers test mode. NOTE 1
fXTAL x M
0
1
PLL
Enabled
Hi-Z
Default SSC; Modulation Factor = ½ Percent
32
PLL Bypass Mode,
1
0
External Disabled
Test Clk
Input
(1MHz≤ Test Clk ≤ 200MHz); NOTE 1
fXTAL x M
1
1
PLL
Disabled
Hi-Z
No SSC Modulation
32
NOTE 1: Used for in house debug and characterization.
TEST_I/O
Source
SSC
TABLE 3B. PROGRAMMABLE VCO FREQUENCY FUNCTION TABLE (NOTE 1)
VCO Frequency
(MHz)
M Count
190
190
256
128
64
32
16
8
4
2
1
M8
M7
M6
M5
M4
M3
M2
M1
M0
0
1
0
1
1
1
1
1
0
191
191
0
1
0
1
1
1
1
1
1
192
192
0
1
1
0
0
0
0
0
0
193
193
0
1
1
0
0
0
0
0
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
508
508
1
1
1
1
1
1
1
0
0
509
509
1
1
1
1
1
1
1
0
1
510
510
1
1
1
1
1
1
1
1
0
NOTE 1: Assumes a 16MHz crystal.
ICS8431CM-11
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3
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
ABSOLUTE MAXIMUM RATINGS
Supply Voltage
Inputs
Outputs
Ambient Operating Temperature
Storage Temperature
4.6V
-0.5V to VDD + 0.5V
-0.5V to VDDO + 0.5V
0°C to 85°C
-65°C to 150°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These ratings
are stress specifications only and functional operation of product at these condition or any conditions beyond those listed in
the DC Characteristics or AC Characteristics is not implied. Exposure to absolute maximum rating conditions for extended
periods may affect product reliability.
TABLE 4A. POWER SUPPLY DC CHARACTERISTICS, VDD = VDDA = VDDI = VDDO = 3.3V±5%, TA = 0°C TO 85°C
Symbol
Parameter
VDD
VDDO
Test Conditions
Minimum
Typical
Maximum
Units
Power Supply Voltage
3.135
3.3
3.465
V
Output Power Supply Voltage
3.135
3.3
3.465
V
VDDA
Analog Power Supply Voltage
3.135
3.3
3.465
V
VDDI
Input Power Supply Voltage
3.135
3.3
3.465
V
140
mA
IEE
TABLE 4B. LVCMOS / LVTTL DC CHARACTERISTICS, VDD = VDDA = VDDI = VDDO = 3.3V±5%, TA = 0°C TO 85°C
Symbol
VIH
VIL
IIH
IIL
Parameter
M0:M8, SSC_CTL0,
Input High Voltage SSC_CTL1, MR,
TEST_I/O, nP_LOAD
M0:M8, SSC_CTL0,
Input Low Voltage SSC_CTL1, MR,
TEST_I/O, nP_LOAD
M7, M8, SSC_CTL0,
SSC_CTL1, TEST_IO
Input High Current
M0:M6,
nP_LOAD, MR
M7, M8, SSC_CTL0,
SSC_CTL1, TEST_IO
Input Low Current
M0:M6,
nP_LOAD, MR
Test Conditions
Minimum
3.135V ≤ VDD ≤ 3.465V
3.135V ≤ VDD ≤ 3.465V
Typical
Maximum
Units
2
VDD + 0.3
V
-0.3
0.8
V
VDD = VIN = 3.465V
5
µA
VDD = VIN = 3.465V
150
µA
VDD = 3.465V, VIN = 0V
-150
µA
VDD = 3.465V, VIN = 0V
-5
µA
TABLE 4C. LVPECL DC CHARACTERISTICS, VDD = VDDA = VDDI = VDDO = 3.3V±5%, TA = 0°C TO 85°C
Symbol
Parameter
Test Conditions
VOH
Output High Voltage; NOTE 1
VOL
Output Low Voltage; NOTE 1
VSWING
Peak-to-Peak Output Voltage Swing
Minimum
Maximum
Units
VDDO - 1.28
VDDO - 0.98
V
VDDO - 2.0
VDDO - 1.7
V
850
mV
600
Typical
700
NOTE 1: Output terminated with 50Ω to VDDO - 2V.
ICS8431CM-11
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4
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
TABLE 5. CRYSTAL CHARACTERISTICS
Parameter
Test Conditions
Minimum
Mode of Oscillation
Typical
Maximum
Units
Fundamental
Frequency
16.0
MHz
Frequency Tolerance
-50
+50
ppm
Frequency Stability
-100
+100
ppm
100
µW
Drive Level
50
Ω
7
pF
32
pF
3
7
nH
0
70
°C
-5
+5
ppm
Equivalent Series Resistance (ESR)
Shunt Capacitance
3
Load Capacitance
10
Series Pin Inductance
Operating Temperature Range
Aging
Per year @25°C
18
TABLE 6. AC CHARACTERISTICS, VDD = VDDA = VDDI = VDDO = 3.3V±5%, TA = 0°C TO 85°C, 16MHZ CRYSTAL
Symbol
Parameter
Test Conditions
Fave
Average Output Frequency; NOTE 4
Minimum
Typical
-750
FOUT = 200 MHz
18
Maximum
Units
+750
ppm
30
ps
35
ps
t j it(cc)
Cycle-to-Cycle Jitter ; NOTE 2
odc
Output Duty Cycle; NOTE 2
53
%
tR
Output Rise Time; NOTE 1, 2
20% to 80%
300
450
600
ps
tF
Output Fall Time; NOTE 1, 2
20% to 80%
300
450
600
ps
Fxtal
Cr ystal Input Range; NOTE 3
SSC Modulation Frequency;
NOTE 1, 2
SSC Modulation Factor ;
NOTE 1, 2
Spectral Reduction; NOTE 1, 2
14
16
20
MHz
33.33
KHz
0.6
%
Fm
Fmf
SSCred
47
30
0.4
7
tSTABLE
Power-up to Stable Clock Output
NOTE 1: Spread Spectrum clocking enabled.
NOTE 2: Outputs terminated with 50Ω to VDDO - 2V.
NOTE 3: Only valid within the VCO operating range.
NOTE 4: Without external cr ystal components.
tjit(cc), tR, tF, odc conform to JEDEC JESD65 definitions.
ICS8431CM-11
10
dB
10
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5
ms
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
80%
➤
PARAMETER MEASUREMENT INFORMATION
80%
Vswing
20%
trise
tfall
➤
FIGURE 1 — INPUT
AND
➤
➤
➤
20%
Clock Inputs
and Outputs
➤
OUTPUT SLEW RATES
FOUT
nFOUT
➤
➤
tcycle
➤
n
tcycle
n+1
➤
t jit(cc) = tcycle n –tcycle n+1
FIGURE 2 — CYCLE-TO-CYCLE JITTER
nFOUT
FOUT
Pulse Width (t
PW
)
t
t
odc =
t
PERIOD
PW
PERIOD
FIGURE 3 — odc & t PERIOD
ICS8431CM-11
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6
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
FUNCTIONAL DESCRIPTION
The ICS8431-11 features a fully integrated PLL and therefore requires no external components for setting the loop bandwidth.
A 16MHz series-resonant, fundamental crystal is used as the input to the on-chip oscillator. The output of the oscillator is divided by
16 prior to the phase detector. With a 16MHz crystal this provides a 1MHz reference frequency. The VCO of the PLL operates over
a range of 190 to 510MHz. The output of the loop divider is also applied to the phase detector.
The phase detector and the loop filter force the VCO output frequency to be M times the reference frequency by adjusting the
VCO control voltage. Note that for some values of M (either too high or too low) the PLL will not achieve lock. The output of the
VCO is scaled by a divider prior to being sent to the LVPECL output buffer. The divider provides a 50% output duty cycle.
The programmable features of the ICS8431-11 support four output operational modes and a programmable PLL loop divider.
The four output operational modes are spread spectrum clocking (SSC), non-spread spectrum clock and two test modes and
are controlled by the SSC_CTL[1:0] pins.
The PLL loop divider or M divider is programmed by using inputs M0 through M8. While the nP_LOAD input is held LOW, the
data present at M0:M8 is transparent to the M-divider. On the LOW-to-HIGH transition of nP_LOAD, the M0:M8 data is latched
into the M-divider and any further changes at the M0:M8 inputs will not be seen by the M-divider until the next LOW transition
on nP_LOAD.
The relationship between the VCO frequency, the crystal frequency and the loop counter/divider is defined as follows:
fxtal x
M
16
The M count and the required values of M0:M8 for programming the VCO are shown in Table 3B, Programmable VCO Frequency
Function Table. The frequency out is defined as follows:
fVCO =
FOUT = fVCO = fxtal x M
2
32
For the ICS8431-11, the output divider equals 2. Valid M values for which the PLL will achieve lock are defined as 190 ≤ M ≤ 510.
ICS8431CM-11
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7
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
AND
OSCILLATOR INTERFACE
The ICS8431-11 features an internal oscillator that uses an
external quartz crystal as the source of its reference frequency.
A 16MHz crystal divided by 16 before being sent to the phase
detector provides the reference frequency. The oscillator is a
series resonant, multi-vibrator type design. This design provides
better stability and eliminates the need for large on chip capacitors.
Though a series resonant crystal is preferred, a parallel resonant
crystal can be used. A parallel resonant mode crystal used in a
series resonant circuit will exhibit a frequency of oscillation a few
hundred ppm lower than specified. A few hundred ppm translates
to KHz inaccuracy. In general computing applications this level
of inaccuracy is irrelevant. If better ppm accuracy is required, an
external capacitor can be added to a parallel resonant crystal in
series to pin 25. Figure 1A shows how to interface with a crystal.
ICS8431-11
XTAL2
(Pin 26, SOIC)
XTAL1
(Pin 25, SOIC)
➤
CRYSTAL INPUT
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
Optional
FIGURE 1A. CRYSTAL INTERFACE
Figures 1A, 1B, and 1C show various crystal parameters
which are recommended only as guidelines. Figure 1A shows
how to interface a capacitor with a parallel resonant crystal.
Figure 1B shows the capacitor value needed for the optimum
PPM performance over various parallel resonant crystals.
Figure 1C shows the recommended tuning capacitance for a
various parallel resonant crystal.
FIGURE 1B. Recommended tuning capacitance for various parallel
resonant crystals.
14.318
Frequency Accuracy (ppm)
Series Capacitor, C1 (pF)
60
FIGURE 1C. Recommended tuning capacitance for various
parallel resonant crystal.
50
15.000
40
16.667
30
19.440
20.000
20
24.000
10
0
14
15
16
17
18
19
20
21
22
23
24
25
Crystal Frequency (MHz)
100
80
60
40
20
0
-20 0
-40
-60
-80
-100
10
20
30
40
50
60
19.44MHz
Series Capacitor, C1 (pF)
16MHz
15.00MHz
ICS8431CM-11
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REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
SPREAD SPECTRUM
Spread-spectrum clocking is a frequency modulation technique for EMI reduction. When spread-spectrum is enabled, a
30KHz triangle waveform is used with 0.5% down-spread
(+0.0% / -0.5%) from the nominal 200MHz clock frequency.
An example of a triangle frequency modulation profile is shown
in Figure 2 below. The ramp profile can be expressed as:
The ICS8431-11 triangle modulation frequency deviation will
not exceed 0.6% down-spread from the nominal clock frequency (+0.0% / -0.5%). An example of the amount of down
spread relative to the nominal clock frequency can be seen in
the frequency domain, as shown in Figure 3. The ratio of this
width to the fundamental frequency is typically 0.4%, and will
not exceed 0.6%. The resulting spectral reduction will be
greater than 7dB, as shown in Figure 3. It is important to note
the ICS8431-11 7dB minimum spectral reduction is the component-specific EMI reduction, and will not necessarily be the
same as the system EMI reduction.
• Fnom = Nominal Clock Frequency in Spread OFF mode
(200MHz with 16MHz IN)
• Fm = Nominal Modulation Frequency (30KHz)
• δ = Modulation Factor (0.5% down spread)
1 ,
2 fm
(1 - δ) fnom - 2 fm x δ x fnom x t when 1 < t < 1
2 fm
fm
➤
(1 - δ) fnom + 2 fm x δ x fnom x t when 0 < t <
Fnom
∆ − 10 dBm
A
B
(1 - δ) Fnom
δ = .4%
➤
0.5/fm
1/fm
FIGURE 3. 200MHZ CLOCK OUTPUT IN FREQUENCY DOMAIN
FIGURE 2. TRIANGLE FREQUENCY MODULATION
(A) SPREAD-SPECTRUM OFF
(B) SPREAD-SPECTRUM ON
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS8431-11 provides
separate power supplies to isolate any high switching noise
from the outputs to the internal PLL. VDD, VDDI, VDDA, and
VDDO should be individually connected to the power supply
plane through vias, and bypass capacitors should be used
for each pin. To achieve optimum jitter performance, better
power supply isolation is required. Figure 4 illustrates how a
10Ω along with a 10µF and a .01µF bypass capacitor should
be connected to each power supply pin.
ICS8431CM-11
3.3V
VDD
.01µF
10Ω
VDDA
.01µF
10 µF
FIGURE 4. POWER SUPPLY FILTERING
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9
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
TERMINATION
FOR
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
PECL OUTPUTS
drive 50Ω transmission lines. Matched impedance techniques
should be used to maximize operating frequency and minimize signal distortion. There are a few simple termination
schemes. Figures 5A and 5B show two different layouts which
are recommended only as guidelines. Other suitable clock layouts may exist and it would be recommended that the board
designers simulate to guarantee compatibility across all printed
circuit and clock component process variations.
The clock layout topology shown below is typical for
IA64/32 platforms. The two different layouts mentioned are
recommended only as guidelines.
FOUT and nFOUT are low impedance follower outputs that
generate ECL/PECL compatible outputs. Therefore, terminating resistors (DC current path to ground) or current sources
must be used for functionality. These outputs are designed to
Zo = 50Ω
3.3V
Zo = 50Ω
5
2 Zo
FOUT
5
2 Zo
FIN
Zo = 50Ω
Zo = 50Ω
Zo = 50Ω
Zo = 50Ω
FOUT
50Ω
Zo = 50Ω
VCC-2V
➤
RTT
1
RTT =
FIN
50Ω
(VOH + VOL / VCC –2) –2
Zo = 50Ω
3
2 Zo
Zo
FIGURE 5A. LVPECL OUTPUT TERMINATION
3
2 Zo
FIGURE 5B. LVPECL OUTPUT TERMINATION
LAYOUT GUIDELINE
The schematic of the ICS8431-11 layout example used in this layout guideline is shown in Figure 6A. The ICS8431-11 recommended
PCB board layout for this example is shown in Figure 6B. This layout example is used as a general guideline. The layout in the actual
system will depend on the selected component types, the density of the components, the density of the traces, and the stacking of
the P.C. board.
U1
VDD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
M0
M1
M2
M3
M4
M5
M6
M7
M8
SSC_CTL0
SSC_CTL1
GND
TEST_IO
VDD
nP_LOAD
VDDI
XTAL1
XTAL2
NC
NC
VDDA
NC
NC
NC
VDDO
FOUT
nFOUT
GND
28
27
26
25
24
23
22
21
20
19
18
17
16
15
C6
0.01uF
VDD
Termination A
X1
R5
VDDA
VDD0
Termination
B (not shown
in the layout)
10
C3
0.01uF
VDD
C4
10uF
IN+
R1
125
IN-
Zo = 50 Ohm
IN+
TL1
8431-11
C1
0.1uF
R3
125
Zo = 50 Ohm
R2
50
R1
50
INC2
0.1uF
TL2
R2
84
R4
84
R3
50
FIGURE 6A. RECOMMENDED SCHEMATIC LAYOUT
ICS8431CM-11
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10
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
The following component footprints are used in this layout
example:
traces should be routed first and should be locked prior to routing
other signals traces.
• The traces with 50Ω transmission lines TL1 and TL2 at
FOUT and nFOUT should have equal delay and run adjacent to each other. Avoid sharp angles on the clock trace.
Sharp angle turns cause the characteristic impedance to
change on the transmission lines.
All the resistors and capacitors are size 0603.
POWER
AND
GROUNDING
Place the decoupling capacitors C1, C2 and C3, C4, C5, C6 as
close as possible to the power pins. If space allows, placing the
decoupling capacitor at the component side is preferred. This can
reduce unwanted inductance between the decoupling capacitor
and the power pin generated by the via.
• Keep the clock trace on same layer. Whenever possible,
avoid any vias on the clock traces. Any via on the trace
can affect the trace characteristic impedance and hence
degrade signal quality.
Maximize the pad size of the power (ground) at the decoupling
capacitor. Maximize the number of vias between power (ground)
and the pads. This can reduce the inductance between the power
(ground) plane and the component power (ground) pins.
• To prevent cross talk, avoid routing other signal traces in
parallel with the clock traces. If running parallel traces is
unavoidable, allow more space between the clock trace
and the other signal trace.
If VDDA shares the same power supply with VDD, insert the RC
filter R5, C3, and C4 in between. Place this RC filter as close to
the VDDA as possible.
CLOCK TRACES
AND
• Make sure no other signal trace is routed between the
clock trace pair.
The matching termination resistors R1, R2, R3 and R4 should be
located as close to the receiver input pins as possible. Other termination scheme can also be used but is not shown in this example.
TERMINATION
The component placements, locations and orientations should
be arranged to achieve the best clock signal quality. Poor clock
signal quality can degrade the system performance or cause
system failure. In the synchronous high-speed digital system,
the clock signal is less tolerable to poor signal quality than other
signals. Any ringing on the rising or falling edge or excessive ring
back can cause system failure. The trace shape and the trace
delay might be restricted by the available space on the board and
the component location. While routing the traces, the clock signal
CRYSTAL
The crystal X1 should be located as close as possible to the pins
26 (XTAL1) and 25 (XTAL2). The trace length between the X1
and U1 should be kept to a minimum to avoid unwanted parasitic
inductance and capacitance. Other signal traces should not be
routed near the crystal traces.
U1
ICS8431-11
GND
C6
VDD
X1
Signals
VIA
C3
C4
R5
Close to the input
pins of the
receiver
R1
C2
R2
TL1 (50 Ohm)
C1
TL2 (50 Ohm)
IN+
INR3
R4
FIGURE 6B. PCB BOARD LAYOUT FOR ICS8431-11
ICS8431CM-11
www.icst.com/products/hiperclocks.html
11
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
PACKAGE OUTLINE - M SUFFIX
C
N
28
15
L
H
E
14
1
h x 45º
α
D
A2
A
e
A1
SEATING
PLANE
B
.10 (.004)
TABLE 7. PACKAGE DIMENSIONS
Millimeters
SYMBOL
Inches
MIN
MAX
MIN
MAX
A
--
2.65
--
0.104
A1
0.10
--
0.0040
--
A2
2.05
2.55
0.081
0.100
B
0.33
0.51
0.013
0.020
N
28
C
0.18
0.32
0.007
0.013
D
17.70
18.40
0.697
0.724
E
7.40
7.60
0.291
0.299
e
H
1.27 BASIC
0.050 BASIC
10.00
10.65
0.394
0.419
h
0.25
0.75
0.010
0.029
L
0.40
1.27
0.016
0.050
α
0°
8°
0°
8°
REFERENCE DOCUMENT: JEDEC PUBLICATION 95, MS-013, MO-119
ICS8431CM-11
www.icst.com/products/hiperclocks.html
12
REV. A JULY 11, 2001
ICS8431-11
Integrated
Circuit
Systems, Inc.
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
TABLE 8. ORDERING INFORMATION
Part/Order Number
Marking
Package
Count
Temperature
ICS8431CM-11
ICS8431CM-11
28 Lead SOIC
26 Per Tube
0°C to 70°C
ICS8431CM-11T
ICS8431CM-11
28 Lead SOIC on Tape and Reel
1000
0°C to 70°C
While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems, Incorporated (ICS) assumes no responsibility for either its use
or for infringement of any patents or other rights of third parties, which would result from its use. No other circuits, patents, or licenses are implied. This product is intended for use
in normal commercial applications. Any other applications such as those requiring extended temperature range, high reliability, or other extraordinary environmental requirements are
not recommended without additional processing by ICS. ICS reserves the right to change any circuitry or specifications without notice. ICS does not authorize or warrant any ICS
product for use in life support devices or critical medical instruments.
ICS8431CM-11
www.icst.com/products/hiperclocks.html
13
REV. A JULY 11, 2001