ics343 Integrated Device Technology, ics343 Datasheet - Page 2

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ics343

Manufacturer Part Number
ics343
Description
Field Programmable Triple Output Spread Spectrum Versaclock Synthesizer
Manufacturer
Integrated Device Technology
Datasheet

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Pin Assignment
Pin Descriptions
External Components
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.
Decoupling Capacitor
As with any high-performance mixed-signal IC, the ICS343
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.
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
IDT™ / ICS™ FIELD PROGRAMMABLE TRIPLE OUTPUT SS VERSACLOCK SYNTHESIZER 2
ICS343
FIELD PROGRAMMABLE TRIPLE OUTPUT SS VERSACLOCK SYNTHESIZER
X 1 / I C L K
C L K 1
G N D
V D D
Number
Pin
1
2
3
4
5
6
7
8
8-pin (150 mil) SOIC
1
2
3
4
X1/ICLK
Name
PDTS
CLK1
CLK3
CLK2
GND
VDD
Pin
X2
8
7
6
5
Output
Output
Output
X 2
P D T S
C L K 2
C L K 3
Power
Power
Type
Input
Pin
XO
XI
Connect this pin to a crystal or external clock input.
Connect to +3.3 V.
Connect to ground.
Clock output. Weak internal pull-down when tri-state.
Clock output. Weak internal pull-down when tri-state.
Clock output. Weak internal pull-down when tri-state.
Powers down entire chip. Tri-states CLK outputs when low. Internal pull-up.
Connect this pin to a crystal, or float for clock input.
Output Clock Selection Table
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) been 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
pF)*2. In this equation, C
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
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
Frequency
Amount
Spread
Output
Pin Description
Configurable
Configurable
CLK2
User
User
L
Configurable
Configurable
= crystal load capacitance in pF.
EPROM CLOCK SYNTHESIZER
CLK2
User
User
ICS343
Configurable
Configurable
CLK3
User
User
REV J 061206
L
-6

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