DATASHEET
NETWORKING AND PCI CLOCK SOURCE
Description
The ICS650-36 is a low cost frequency generator designed
to support networking and PCI applications. Using
analog/digital Phase Locked-Loop (PLL) techniques, the
device uses a standard fundamental mode, inexpensive
crystal input of 25 MHz to produce four output clocks
supporting LAN, PCI, and 100M SDRAM functions.
The device also has a power down feature that tri-states the
clock outputs and turns off the PLL when the PDTS pin is
taken low.
ICS650-36
Features
•
•
•
•
•
•
•
•
•
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Packaged in 16-pin TSSOP
Pb (lead) free package
Replaces multiple crystals and oscillators
Input crystal or clock frequency of 25 MHz
Fixed reference output frequency of 25 MHz
Selectable output frequencies of 33.3, 33.333, 50,
66.666, 100, and 125 MHz
Duty cycle of 40/60
Operating voltage of 3.3 V
Advanced, low-power CMOS process
Industrial and commercial temperature ranges
Block Diagram
VDD
3
S2:0
3
Select/
Control
Circuit
PLL1
CLK1
PLL2
CLK2
PLL3
X1/ICLK
25 MHz
crystal
input
X2
Crystal
Oscillator/
Clock
Buffer
CLK3
REF
External capacitors
may be required.
3
GND
PDTS
(all outputs and PLLs)
IDT™ / ICS™
NETWORKING AND PCI CLOCK SOURCE
1
ICS650-36
REV F 051310
ICS650-36
NETWORKING AND PCI CLOCK SOURCE
CLOCK SYNTHESIZER
Pin Assignment
X2
X1
GND
CLK3
PDTS
S2
CLK2
VDD
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VDD
GND
REF
S0
VDD
CLK1
GND
S1
CLK Output 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
REF
OFF
ON
ON
ON
ON
ON
ON
ON
CLK1
33.30
33.333
33.333
66.666
33.333
33.333
33.333
33.30
CLK2
50
33.333
66.666
66.666
50
50
66.666
50
CLK3
125
125
125
125
125
100
100
125
16-pin (173 mil) TSSOP
Note: All frequencies are in MHz.
Pin Descriptions
Pin
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
Pin
Name
X2
X1
GND
CLK3
Pin
Type
Output
Input
Power
Output
Pin Description
Crystal connection. Connect to 25 MHz crystal input or float for
clock.
Crystal connection. Connect to 25 MHz crystal or clock input.
Connect to ground.
Selectable clock output. See table above for frequency. Weak
internal pull-down when tri-state.
Powers down entire chip and tri-states outputs when low. Internal
pull-up resistor.
Select pin. Selects clock output frequency from table above.
Internal pull-up resistor.
Selectable clock output. See table above for frequency. Weak
internal pull-down when tri-state.
Connect to +3.3 V.
Select pin. Selects clock output frequency from table above.
Internal pull-up resistor.
Connect to ground.
Selectable clock output. See table above for frequency. Weak
internal pull-down when tri-state.
Connect to +3.3 V.
Select pin. Selects clock output frequency from table above.
Internal pull-up resistor.
PDTS
S2
CLK2
VDD
S1
GND
CLK1
VDD
S0
Input
Input
Output
Power
Input
Power
Output
Power
Input
IDT™ / ICS™
NETWORKING AND PCI CLOCK SOURCE
2
ICS650-36
REV F 051310
ICS650-36
NETWORKING AND PCI CLOCK SOURCE
CLOCK SYNTHESIZER
Pin
Number
14
15
16
Pin
Name
REF
GND
VDD
Pin
Type
Output
Power
Power
Pin Description
Reference 25 MHz clock output. Weak internal pull-down when
tri-state.
Connect to ground.
Connect to +3.3 V.
External Components
Decoupling Capacitor
As with any high performance mixed-signal IC, the
ICS650-36 must be isolated from system power supply
noise to perform optimally.
A decoupling capacitor of 0.01µF must be connected
between each VDD and the PCB ground plane.
Example: For a crystal with a 16 pF load capacitance, each
crystal capacitor would be 20 pF [(16-6) x 2 = 20].
PCB Layout Recommendations
Observed the following guidelines for optimum device
performance and lowest output phase noise:
1) The 0.01µF decoupling capacitors should be mounted on
the component side of the board as close to the VDD pin as
possible. No vias should be used between the decoupling
capacitors and VDD pins. The PCB trace to VDD pins
should be kept as short as possible, as should the PCB
trace to the ground via.
2) The external crystal should be mounted just next to the
device with short traces. The X1 and X2 traces should not
be routed next to each other with minimum spaces, instead
they should be separated and away from other traces.
3) Place the 33Ω series termination resistor (if needed)
close to the clock output to minimize EMI.
4) An optimum layout is one with all components on the
same side of the board, minimizing vias through other signal
layers. Other signal traces should be routed away from the
ICS650-36. This includes signal traces just underneath the
device, or on layers adjacent to the ground plane layer used
by the device.
Series Termination Resistor
Clock output traces over one inch should use series
termination. To series terminate a 50Ω trace (a commonly
used trace impedance), place a 33Ω resistor in series with
the clock line, as close to the clock output pin as possible.
The nominal impedance of the clock output is 20Ω
.
Crystal Load Capacitors
The device crystal connections should include pads for
small capacitors from X1 to ground and from X2 to ground.
These capacitors are used to adjust the stray capacitance of
the board to match the nominally required crystal load
capacitance. Because load capacitance can only be
increased in this trimming process, it is important to keep
stray capacitance to a minimum by using very short PCB
traces (and no vias) between the crystal and device. Crystal
capacitors must be connected from each of the pins X1 and
X2 to ground.
The value (in pF) of these crystal caps should equal (C
L
-6
pF)*2. In this equation, C
L
= crystal load capacitance in pF.
IDT™ / ICS™
NETWORKING AND PCI CLOCK SOURCE
3
ICS650-36
REV F 051310
ICS650-36
NETWORKING AND PCI CLOCK SOURCE
CLOCK SYNTHESIZER
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS650-36. These ratings, which are
standard values for IDT commercially rated parts, 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
Supply Voltage, VDD
All Inputs and Outputs
Ambient Operating Temperature (commercial)
Ambient Operating Temperature (industrial)
Storage Temperature
Junction Temperature
Soldering Temperature
-0.5 V to 7 V
Rating
-0.5 V to VDD+0.5 V
0 to +70° C
-40 to +85° C
-65 to +150° C
125° C
260° C
Recommended Operation Conditions
Parameter
Ambient Operating Temperature (commercial)
Ambient Operating Temperature (industrial)
Power Supply Voltage (measured in respect to GND)
Min.
0
-40
+3.135
Typ.
Max.
+70
+85
Units
°
C
°
C
V
+3.3
+3.465
IDT™ / ICS™
NETWORKING AND PCI CLOCK SOURCE
4
ICS650-36
REV F 051310
ICS650-36
NETWORKING AND PCI CLOCK SOURCE
CLOCK SYNTHESIZER
DC Electrical Characteristics
Unless stated otherwise,
VDD = 3.3 V ±5%,
Ambient Temperature -40 to +85° C
Parameter
Operating Voltage
Supply Current
Power Down Current
Input High Voltage
Input Low Voltage
Output High Voltage
Output High Voltage
Output Low Voltage
Short Circuit Current
Input Capacitance, inputs
Nominal Output Impedance
Internal Pull-up Resistor
Internal Pull-down Resistor
Symbol
VDD
IDD
IDDPD
V
IH
V
IL
V
OH
V
OH
V
OL
I
OS
C
IN
Z
OUT
R
PU
R
PD
Conditions
No load, PDTS=1
No load, PDTS=0
PDTS, S2:0
PDTS, S2:0
I
OH
= -4 mA
I
OH
= -12 mA
I
OL
= 12 mA
Clock outputs
Min.
3.135
Typ.
3.3
25
100
Max.
3.465
Units
V
mA
µA
V
2
0.8
VDD-0.3
2.4
0.4
±65
5
20
V
V
V
V
mA
pF
Ω
kΩ
kΩ
PDTS, S2:0
Outputs
500
250
AC Electrical Characteristics
Unless stated otherwise,
VDD = 3.3 V ±5%,
Ambient Temperature -40 to +85° C
Parameter
Input Frequency
Output Rise Time
Output Fall Time
Output Clock Duty Cycle
Absolute Clock Period Jitter
Clock Jitter, Cycle-to-Cycle
Clock Jitter, Long Term
Frequency Synthesis Error
Output Enable Time
Output Disable Time
Symbol
f
IN
t
OR
t
OF
Conditions
20% to 80%, Note 1
80% to 20%, Note 1
at VDD/2, Note 1
Note 1
33.333M, 66.666M,
Note 1
25M, n=1000, Note1
Min.
Typ.
25
0.8
0.7
Max. Units
MHz
ns
ns
60
%
ps
ps
ps
ppm
µs
ns
40
±125
150
900
0
350
25
t
OE
t
OD
PDTS high to output
locked to ±1%
PDTS low to tri-state
Note 1: Measured with a 15 pF load.
IDT™ / ICS™
NETWORKING AND PCI CLOCK SOURCE
5
ICS650-36
REV F 051310
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