ICS341
FIELD PROGRAMMABLE SS VERSACLOCK SYNTHESIZER
EPROM CLOCK SYNTHESIZER
Pin Assignment
X1/ I CLK
VDD
GND
S0
1
2
3
4
8
7
6
5
X2
PDTS
S1
CLK
Output Clock Selection Table
S1
0
0
1
1
S0
0
1
0
1
CLK (MHz)
User
Configurable
User
Configurable
User
Configurable
User
Configurable
Spread
Percentage
User
Configurable
User
Configurable
User
Configurable
User
Configurable
8-pin (150 mil) SOIC
Pin Descriptions
Pin
Number
1
2
3
4
5
6
7
8
Pin
Name
X1/ICLK
VDD
GND
S0
CLK
S1
PDTS
X2
Pin
Type
XI
Power
Power
Input
Output
Input
Input
XO
Connect to +3.3 V.
Connect to ground.
Pin Description
Connect this pin to a crystal or external clock input.
Select pin 0 for frequency selection on CLK. Internal pull-up resistor.
Clock output. Weak internal pull-down when tri-state.
Select pin 1 for frequency selection on CLK. Internal pull-up resistor.
Powers down entire chip. Tri-states CLK outputs when low. Internal pull-up
resistor.
Connect this pin to a crystal, or float for clock input.
External Components
Series Termination Resistor
Clock output traces over one inch should use series
termination. To series terminate a 50 trace (a commonly
used trace impedance), place a 33 resistor in series with
the clock line, as close to the clock output pin as possible.
The nominal impedance of the clock output is 20.
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.
Example: For a crystal with a 16 pF load capacitance, each
crystal capacitor would be 20 pF [(16-6) x 2] = 20.
Decoupling Capacitor
As with any high-performance mixed-signal IC, the ICS341
must be isolated from system power supply noise to perform
optimally.
A decoupling capacitor of 0.01µF must be connected
between VDD and the PCB ground plane.
PCB Layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
1) The 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 the 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.
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.
2
ICS341
REV M 090613
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
IDT® / ICS™
FIELD PROGRAMMABLE SS VERSACLOCK SYNTHESIZER
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
