PI6C557-05
PCIe® 2.0 Clock Generator with 4 HCSL Outputs
Product Features
Î
Î
Î
Î
Î
Î
Î
Î
Î
Î
Î
Description
The PI6C557-05 is a spread spectrum clock generator compliant
to PCI Express® 2.0 and Ethernet requirements. The device is
used for PC or embedded systems to substantially reduce Elec-
tromagnetic Interference (EMI).
The PI6C557-05 provides four differential (HCSL) or LVDS
spread spectrum outputs. The PI6C557-05 is configured to select
spread and clock selection. Using Pericom's patented Phase-
Locked Loop (PLL) techniques, the device takes a 25MHz crys-
tal input and produces four pairs of differential outputs (HCSL)
at 100MHz and 200MHz clock frequencies. It also provides
spread selection of -0.5%, -1.0%, -1.5%, and no spread.
PCIe
®
2.0 complaint
→Phase jitter - 2.1ps RMS (typ)
LVDS compatible outputs
Supply voltage of 3.3V ±5%
25MHz crystal or clock input frequency
HCSL outputs, 0.7V Current mode differential pair
Jitter 40ps cycle-to-cycle (typ)
Spread of -0.5%, -1.0%, -1.5%, and no spread
Industrial temperature range
Spread Bypass option available
Spread and frequency selection via external pins
Packaging: (Pb-free and Green)
→20-pin, 173-mil wide TSSOP
Block Diagram
VDD
2
Pin Configuration
PD
OE
VDDXD
S0
S1
CLK0
CLK0
CLK1
CLK1
CLK2
CLK2
CLK3
CLK3
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
CLK0
CLK0
CLK1
CLK1
GNDODA
VDDODA
CLK2
CLK2
CLK3
CLK3
S[2:0]
3
Spread
Spectrum/
Output
clock
selection
SS Circuitry
S2
X1
X2
PD
OE
GNDXD
IREF
25 MHz
Crystal
crystal
Driver
or clock
X2
Pulling
Capacitors
X1/CLK
PLL
2
Rr(IREF)
GND
All trademarks are property of their respective owners.
11-0063
1
www.pericom.com
P-0.1
04/29/11
PCIe® 2.0 Clock Generator with 4 HCSL Outputs
PI6C557-05
Pin Description
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Pin Name
VDDXD
S0
S1
S2
X1
X2
PD
OE
GND
IREF
CLK3
CLK3
CLK2
CLK2
VDDODA
GND
CLK1
CLK1
CLK0
CLK0
I/O Type Description
Power
Input
Input
Input
Input
Output
Input
Input
Power
Output
Output
Output
Output
Output
Power
Power
Output
Output
Output
Output
Connect to a +3.3V source.
Spread Spectrum Select pin #0. See Spread Spectrum Selection table. Internal pull-up resistor.
Spread Spectrum Select pin #1. See Spread Spectrum Selection table. Internal pull-up resistor.
Spread Spectrum Select pin #2. See Spread Spectrum Selection table. Internal pull-up resistor.
Crystal connection.
Crystal connection.
Power down. Internal pull-up resistor.
Output enable. Tri-states output (High=enable outputs); Low=disable outputs). Internal pull-
up resistor.
Connect to digital circuit ground.
Precision resistor attached to this pin is connected to the internal current reference.
Selectable 100/200 MHz Spread Spectrum differential compliment output clock 3.
Selectable 100/200 MHz Spread Spectrum differential true output clock 3.
Selectable 100/200 MHz Spread Spectrum differential compliment output clock 2.
Selectable 100/200 MHz Spread Spectrum differential true output clock 2.
Connect to a +3.3V analog source.
Output and Analog circuit ground
Selectable 100/200 MHz Spread Spectrum differential compliment output clock 1.
Selectable 100/200 MHz Spread Spectrum differential true output clock 1.
Selectable 100/200 MHz Spread Spectrum differential compliment output clock 0.
Selectable 100/200 MHz Spread Spectrum differential true output clock 0.
Table 2: Spread Selection Table
S2
0
0
0
0
1
1
1
1
S1
0
0
1
1
0
0
1
1
S0
0
1
0
1
0
1
0
1
Spread %
-0.5
-1.0
-1.5
No Spread
-0.5
-1.0
-1.5
No Spread
Spread Type
Down
Down
Down
Not Applicable
Down
Down
Down
Not Applicable
Output Frequency
100
100
100
100
200
200
200
200
All trademarks are property of their respective owners.
11-0063
2
www.pericom.com
P-0.1
04/29/11
PCIe® 2.0 Clock Generator with 4 HCSL Outputs
PI6C557-05
Application Information
Decoupling Capacitors
Decoupling capacitors of 0.01μF or 0.1μF must be connected
between each VDD pin and the PCB ground plane and placed
as close to the VDD pin as possible.
PI6C557-05 must be isolated from system power supply noise to
perform optimally.
Output Structures
IREF =2.3mA
6*IREF
Crystal
Use a 25MHz fundamental mode parallel resonant crystal with
less than 30PPM of error across temperature.
R
R
=475
Ω
See Output Termination
Sections
Current Source (Iref) Reference Resistor - RR
If board target trace impedance is 50-Ohm,
then RR = 475-Ohm providing an IREF of 2.32 mA. The output
current (IOH) is 6*IREF.
Output Termination
The PCI-Express differential clock outputs of the PI6C557-05
are open source drivers and require an external series resistor
and a resistor to ground. These resistor values and their allow-
able locations are shown in detail in the PCI-Express Layout
Guidelines section.
The PI6C557-05 can be configured for LVDS compatible voltage
levels. See the LVDS Compatible Layout Guidelines section.
All trademarks are property of their respective owners.
11-0063
3
www.pericom.com
P-0.1
04/29/11
PCIe® 2.0 Clock Generator with 4 HCSL Outputs
PI6C557-05
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.
R
S
R
T
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 min to 14 max
0.225 min to 12.6 max
Unit
inch
inch
PCI-Express Device Routing
L1
L1’
R
S
R
S
L2
L2’
R
T
L3’
R
T
L3
L4
L4’
PI6C557-05
Output
Clock
PCI-Express
Load or
Connector
Typical PCI-Express (HCSL) Waveform
700 mV
0
t
OR
0.52 V
0.175 V
500 ps
500 ps
t
OF
0.52 V
0.175 V
All trademarks are property of their respective owners.
11-0063
4
www.pericom.com
P-0.1
04/29/11
PCIe® 2.0 Clock Generator with 4 HCSL Outputs
PI6C557-05
Application Information
LVDS Recommendations for Differential Routing
L1 length, route as non-coupled 50-Ohm trace.
L2 length, route as non-coupled 50-Ohm trace.
R
P
R
Q
R
T
L3 length, route as 100Ω differential trace.
L3 length, route as 100Ω differential trace.
Dimension or Value
0.5 max
0.2 max
100
100
150
Unit
inch
inch
Ohm
Ohm
Ohm
LVDS Device Routing
L1
R
Q
L1’
L3
L3’
R
P
R
T
PI6C557-05
Clock
Output
L2’
L2
R
T
LVDS
Device
Load
Typical LVDS Waveform
1325 mV
1000 mV
t
OR
500 ps
500 ps
t
OF
1250 mV
1150 mV
1250 mV
1150 mV
All trademarks are property of their respective owners.
11-0063
5
www.pericom.com
P-0.1
04/29/11
京公网安备 11010802033920号
EEWORLD
