ICST ICS557G-05ATR Quad differential pci-express clock source Datasheet

ICS557-05A
Quad Differential PCI-Express Clock Source
Description
Features
The ICS557-05A is a spread-spectrum clock generator
that supports PCI-Express requirements. It is used in
PC or embedded systems to substantially reduce
electro-magnetic interference (EMI). The device
provides four differential HCSL or LVDS high-frequency
outputs with spread spectrum capability. The output
frequency and spread type are selectable using
external pins.
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Packaged in 20-pin TSSOP
Available in Pb (lead) free package
Supports PCI-Express applications
Four differential spread spectrum clock outputs
Spread spectrum for EMI reduction
Uses external 25 MHz clock or crystal input
Power down pin turns off chip
OE control tri-states outputs
Spread and frequency selection via external pins
Spread Bypass option available
Industrial temperature range available
Block Diagram
VDD
2
SEL[2:0]
Spread
Spectrum/
Output
clock
selection
3
PD
OE
Spread
Spectrum
Circuitry
CLKOUTA
25 MHz
crystal or
clock
X1
CLKOUTA
CLKOUTB
Clock
Oscillator
PLL Clock
Synthesis
X2
CLKOUTB
CLKOUTC
CLKOUTC
CLKOUTD
CLKOUTD
Optional tuning crystal
capacitors
2
Rr(IREF)
GND
1
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ICS557-05A
Quad Differential PCI-Express Clock Source
Pin Assignment
VDDXD
1
20
CLKA
S0
2
19
CLKA
S1
3
18
CLKB
S2
4
17
CLKB
X1
5
16
GNDODA
X2
6
15
VDDODA
PD
7
14
CLKC
OE
8
13
CLKC
GNDXD
9
12
CLKD
10
11
CLKD
IREF
20-pin (173 mil) TSSOP
Spread Spectrum Selection Table
S2
S1
S0
Spread%
Spread Type
Output
Frequency (MHz)
0
0
0
-0.5
Down
100
0
0
1
-1.0
Down
100
0
1
0
-1.5
Down
100
0
1
1
No Spread
Not Applicable
100
1
0
0
-0.5
Down
200
1
0
1
-1.0
Down
200
1
1
0
-1.5
Down
200
1
1
1
No Spread
Not Applicable
200
2
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ICS557-05A
Quad Differential PCI-Express Clock Source
Pin Descriptions
Pin
Pin
Name
Pin
Type
1
VDDXD
Power
Connect to +3.3 V digital supply.
2
S0
Input
Spread spectrum select pin #0. See table above. Internal pull-up resistor.
3
S1
Input
Spread spectrum select pin #1. See table above Internal pull-up resistor.
4
S2
Input
Spread spectrum select pin #2. See table above. Internal pull-up resistor.
5
X1
Input
Crystal connection. Connect to a fundamental mode crystal or clock input.
6
X2
Output
Crystal connection. Connect to a fundamental mode crystal or leave open.
7
PD
Input
Powers down all PLL’s and tri-states outputs when low. Internal pull-up resistor.
8
OE
Input
Provides output on, tri-states output (High = enable outputs; Low = disable outputs).
Internal pull-up resistor.
Pin Description
9
GND
Power
Connect to digital ground.
10
IREF
Output
Precision resistor attached to this pin is connected to the internal current reference.
11
CLKD
Output
Selectable 100/200 MHz spread spectrum differential Compliment output clock D.
12
CLKD
Output
Selectable 100/200 MHz spread spectrum differential True output clock D.
13
CLKC
Output
Selectable 100/200 MHz spread spectrum differential Compliment output clock C.
14
CLKC
Output
Selectable 100/200 MHz spread spectrum differential True output clock C.
15
VDDODA
Power
Connect to +3.3 V analog supply.
16
GND
Power
Connect to analog ground.
17
CLKB
Output
Selectable 100/200 MHz spread spectrum differential Compliment output clock B.
18
CLKB
Output
Selectable 100/200 MHz spread spectrum differential True output clock B.
19
CLKA
Output
Selectable 100/200 MHz spread spectrum differential Compliment output clock A.
20
CLKA
Output
Selectable 100/200 MHz spread spectrum differential True output clock A.
3
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ICS557-05A
Quad Differential PCI-Express Clock Source
Application Information
Decoupling Capacitors
Load Resistors RL
As with any high-performance mixed-signal IC, the
ICS557-05A must be isolated from system power
supply noise to perform optimally.
Since the clock outputs are open source outputs, 50
ohm external resistors to ground are to be connected at
each clock output.
Decoupling capacitors of 0.01µF must be connected
between each VDD and the PCB ground plane.
Output Termination
PCB Layout Recommendations
For optimum device performance and lowest output
phase noise, the following guidelines should be
observed.
Each 0.01µF decoupling capacitor should be mounted
on the component side of the board as close to the
VDD pin as possible. No vias should be used between
decoupling capacitor and VDD pin. The PCB trace to
VDD pin should be kept as short as possible, as should
the PCB trace to the ground via. Distance of the ferrite
bead and bulk decoupling from the device is less
critical.
The PCI-Express differential clock outputs of the
ICS557-05A are open source drivers and require an
external series resistor and a resistor to ground. These
resistor values and their allowable locations are shown
in detail in the PCI-Express Layout Guidelines
section.
The ICS557-05A can also be configured for LVDS
compatible voltage levels. See the LVDS Compatible
Layout Guidelines section.
2) An optimum layout is one with all components on the
same side of the board, minimizing vias through other
signal layers (the ferrite bead and bulk decoupling
capacitor can be mounted on the back). Other signal
traces should be routed away from the ICS557-05A.
This includes signal traces just underneath the device,
or on layers adjacent to the ground plane layer used by
the device.
External Components
A minimum number of external components are
required for proper operation. Decoupling capacitors of
0.01 µF should be connected between VDD and GND
pairs (1,9 and 15,16) as close to the device as possible.
On chip capacitors- Crystal capacitors should be
connected from pins X1 to ground and X2 to ground to
optimize the initial accuracy. The value (in pf) of these
crystal caps equal (CL-12)*2 in this equation,
CL=crystal load capacitance in pf. For example, for a
crystal with a 16 pF load cap, each external crystal cap
would be 8 pF. [(16-12)x2]=8.
Current Reference Source Rr (Iref)
If board target trace impedance (Z) is 50Ω, then Rr =
475Ω (1%), providing IREF of 2.32 mA, output current
(IOH) is equal to 6*IREF.
4
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ICS557-05A
Quad Differential PCI-Express Clock Source
Output Structures
6*IREF
IREF
=2.3 mA
R R 475Ω
See Output Termination
Sections - Pages 3 ~ 5
General PCB Layout Recommendations
For optimum device performance and lowest output
phase noise, the following guidelines should be
observed.
1. Each 0.01µF decoupling capacitor should be
mounted on the component side of the board as close
to the VDD pin as possible.
2. No vias should be used between decoupling
capacitor and VDD pin.
3. The PCB trace to VDD pin should be kept as short
as possible, as should the PCB trace to the ground via.
Distance of the ferrite bead and bulk decoupling from
the device is less critical.
4. An optimum layout is one with all components on the
same side of the board, minimizing vias through other
signal layers (any ferrite beads and bulk decoupling
capacitors can be mounted on the back). Other signal
traces should be routed away from the
ICS557-05A.This includes signal traces just
underneath the device, or on layers adjacent to the
ground plane layer used by the device.
5
MDS 557-05A E
Integrated Circuit Systems, Inc.
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525 Race Street, San Jose, CA 95126
Revision 011606
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ICS557-05A
Quad Differential PCI-Express Clock Source
PCI-Express Layout Guidelines
Common Recommendations for Differential Routing
L1 length, Route as non-coupled 50 ohm trace.
L2 length, Route as non-coupled 50 ohm trace.
L3 length, Route as non-coupled 50 ohm trace.
RS
RT
Dimension or Value
0.5 max
0.2 max
0.2 max
33
49.9
Unit
inch
inch
inch
ohm
ohm
Differential Routing on a Single PCB
L4 length, Route as coupled microstrip 100 ohm differential trace.
L4 length, Route as coupled stripline 100 ohm differential trace.
Dimension or Value
2 min to 16 max
1.8 min to 14.4 max
Unit
inch
inch
Differential Routing to a PCI Express Connector
L4 length, Route as coupled microstrip 100 ohm differential trace.
L4 length, Route as coupled stripline 100 ohm differential trace.
Dimension or Value
0.25 to 14 max
0.225 min to 12.6 max
Unit
inch
inch
PCI-Express Device Routing
L1
L2
L4
RS
L1’
L4’
L2’
RS
RT
ICS557-05A
Output
Clock
L3’
RT
PCI-Express
Load or
Connector
L3
Typical PCI-Express (HCSL)
Waveform
700 mV
0
tOR
500 ps
500 ps
0.52 V
0.175 V
0.52 V
0.175 V
6
MDS 557-05A E
Integrated Circuit Systems, Inc.
tOF
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525 Race Street, San Jose, CA 95126
Revision 011606
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ICS557-05A
Quad Differential PCI-Express Clock Source
LVDS Compatible Layout Guidelines
LVDS Recommendations for Differential Routing
L1 length, Route as non-coupled 50 ohm trace.
L2 length, Route as non-coupled 50 ohm trace.
RP
RQ
RT
L3 length, Route as coupled 50 ohm differential trace.
L3 length, Route as coupled 50 ohm differential trace.
Dimension or Value
0.5 max
0.2 max
100
100
150
Unit
inch
inch
ohm
ohm
ohm
LVDS Device Routing
L1
L3
RQ
L1’
RT
ICS557-05A
Clock
Output
RP
L3’
RT
L2’
LVDS
Device
Load
L2
Typical LVDS Waveform
1325 mV
1000 mV
tOR
500 ps
500 ps
1250 mV
1150 mV
1250 mV
1150 mV
7
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ICS557-05A
Quad Differential PCI-Express Clock Source
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS557-05A. These ratings
are stress ratings only. Functional operation of the device at these or any other conditions above those
indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum
rating conditions for extended periods can affect product reliability. Electrical parameters are guaranteed
only over the recommended operating temperature range.
Item
Rating
Supply Voltage, VDD, VDDA
5.5 V
All Inputs and Outputs
-0.5 V to VDD+0.5 V
Ambient Operating Temperature (commercial)
0 to +70°C
Ambient Operating Temperature (industrial)
-40 to +85°C
Storage Temperature
-65 to +150°C
Junction Temperature
125°C
Soldering Temperature
260°C
ESD Protection (Input)
2000 V min. (HBM)
DC Electrical Characteristics
Unless stated otherwise, VDD = 3.3 V ±5%, Ambient Temperature -40 to +85°C
Parameter
Symbol
Supply Voltage
Conditions
V
1
Min.
Typ.
Max.
3.135
3.465
Units
Input High Voltage
VIH
2.0
VDD +0.3
V
Input Low Voltage1
VIL
VSS-0.3
0.8
V
Input Leakage Current2
IIL
0 < Vin < VDD
-5
5
µA
Operating Supply Current
IDD
50Ω, 2pF load@ 100MHz
Input Capacitance
Output Capacitance
105
mA
IDDOE
OE =Low
40
mA
IDDPD
No load, PD =Low
500
µA
CIN
COUT
Input pin capacitance
7
pF
Output pin capacitance
6
pF
Pin Inductance
LPIN
Output Resistance
Rout
CLK outputs
Pull-up Resistance
RPUP
OE, SEL, PD pins
5
1 Single edge is monotonic when transitioning through
2 Inputs with pull-ups/-downs are not included.
●
nH
kΩ
110
kΩ
region.
8
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ICS557-05A
Quad Differential PCI-Express Clock Source
AC Electrical Characteristics - CLKOUTA/CLKOUTB
Unless stated otherwise, VDD=3.3 V ±5%, Ambient Temperature -40 to +85°C
Parameter
Symbol
Conditions
Min.
Input Frequency
Typ.
Max.
25
Output Frequency
MHz
HCSL termination
200
MHz
LVDS termination
100
MHz
850
mV
1,2
Output High Voltage
VOH
660
700
Output Low Voltage1,2
VOL
-150
0
250
350
Crossing Point
Voltage1,2
Absolute
Crossing Point
Voltage1,2,4
Variation over all edges
Jitter, Cycle-to-Cycle1,3
Rise Time1,2
1,2
Fall Time
mV
550
mV
140
mV
60
Modulation Frequency
Units
ps
Spread spectrum
30
31.5
33
kHz
tOR
From 0.175 V to 0.525 V
175
332
700
ps
tOF
From 0.525 V to 0.175 V
175
344
700
ps
Skew between outputs
At crossing point Voltage
Duty Cycle1,3
45
50
ps
55
%
5
All outputs
10
us
5
All outputs
10
us
Output Enable Time
Output Disable Time
Power-up Time
tSTABLE
Spread Change Time
tSPREAD Settling period after spread change
From power-up VDD=3.3 V
3.0
ms
3.0
ms
1
Test setup is RL=50 ohms with 2 pF, Rr = 475Ω (1%).
2
Measurement taken from a single-ended waveform.
3
Measurement taken from a differential waveform.
4
Measured at the crossing point where instantaneous voltages of both CLKOUT and CLKOUT are equal.
5
CLKOUT pins are tri-stated when OE is low. asserted. CLKOUT is driven differential when OE is high unless its
PD= low.
Thermal Characteristics
Parameter
Symbol
Thermal Resistance Junction to
Ambient
Thermal Resistance Junction to Case
Min.
Typ.
Max. Units
θJA
Still air
93
°C/W
θJA
1 m/s air flow
78
°C/W
θJA
3 m/s air flow
65
°C/W
20
°C/W
θJC
9
MDS 557-05A E
Integrated Circuit Systems, Inc.
Conditions
●
525 Race Street, San Jose, CA 95126
Revision 011606
●
tel (408) 297-1201
●
www.icst.com
ICS557-05A
Quad Differential PCI-Express Clock Source
PCI-Express Layout Guidelines
Common Recommendations for Differential Routing
L1 length, Route as non-coupled 50 ohm trace.
L2 length, Route as non-coupled 50 ohm trace.
L3 length, Route as non-coupled 50 ohm trace.
RS
RT
Dimension or Value
0.5 max
0.2 max
0.2 max
33
49.9
Unit
inch
inch
inch
ohm
ohm
Differential Routing on a Single PCB
L4 length, Route as coupled microstrip 100 ohm differential trace.
L4 length, Route as coupled stripline 100 ohm differential trace.
Dimension or Value
2 min to 16 max
1.8 min to 14.4 max
Unit
inch
inch
Differential Routing to a PCI Express Connector
L4 length, Route as coupled microstrip 100 ohm differential trace.
L4 length, Route as coupled stripline 100 ohm differential trace.
Dimension or Value
0.25 to 14 max
0.225 min to 12.6 max
Unit
inch
inch
PCI-Express Device Routing
L1
L2
L4
RS
L1’
L4’
L2’
RS
RT
ICS557-03
Output
Clock
L3’
RT
PCI-Express
Load or
Connector
L3
Typical PCI-Express (HCSL) Waveform
700 mV
0
tOR
500 ps
0.52 V
0.175 V
tOF
0.52 V
0.175 V
10
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Integrated Circuit Systems, Inc.
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ICS557-05A
Quad Differential PCI-Express Clock Source
Package Outline and Package Dimensions (20-pin TSSOP, 173 mil Body)
Package dimensions are kept current with JEDEC Publication No. 95, MO-153
Millimeters
20
Symbol
E1
E
INDEX
AREA
1 2
D
Max
1.20
0.05
0.15
0.80
1.05
0.19
0.30
0.09
0.20
6.40
6.60
6.40 BASIC
4.30
4.50
0.65 Basic
0.45
0.75
0°
8°
-0.10
Min
Max
0.047
0.002
0.006
0.032
0.041
0.007
0.012
0.0035 0.008
0.252
0.260
0.252 BASIC
0.169
0.177
0.0256 Basic
0.018
0.030
0°
8°
-0.004
*For reference only. Controlling dimensions in mm.
A
A2
Min
A
A1
A2
b
c
D
E
E1
e
L
α
aaa
Inches*
A1
c
-Ce
SEATING
PLANE
b
L
aaa C
11
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Integrated Circuit Systems, Inc.
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525 Race Street, San Jose, CA 95126
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ICS557-05A
Quad Differential PCI-Express Clock Source
Ordering Information
Part / Order Number
Marking
Shipping Packaging
Package
Temperature
ICS557G-05A
ICS557G-05A
Tubes
20-pin TSSOP
0 to +70°C
ICS557G-05ATR
ICS557G-05A
Tape and Reel
20-pin TSSOP
0 to +70°C
ICS557G-05ALF
557G-05ALF
Tubes
20-pin TSSOP
0 to +70°C
ICS557G-05ALFTR
557G-05ALF
Tape and Reel
20-pin TSSOP
0 to +70°C
ICS557GI-05A
557GI-05A
Tubes
20-pin TSSOP
-40 to +85°C
ICS557GI-05ATR
557GI-05A
Tape and Reel
20-pin TSSOP
-40 to +85°C
ICS557GI-05ALF
557GI05ALF
Tubes
20-pin TSSOP
-40 to +85°C
ICS557GI-05ALFTR
557GI05ALF
Tape and Reel
20-pin TSSOP
-40 to +85°C
Parts that are ordered with a “LF” suffix to the part number are the Pb-Free configuration and are RoHS compliant.
While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems (ICS)
assumes no responsibility for either its use or for the 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.
12
MDS 557-05A E
Integrated Circuit Systems, Inc.
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525 Race Street, San Jose, CA 95126
Revision 011606
●
tel (408) 297-1201
●
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