ICS345
Triple PLL Field Programmable SS VersaClock Synthesizer
frequencies; thus, lowering a system’s electromagnetic
interference (EMI). The modulation rate is the time from
transitioning from a minimum frequency to a maximum
frequency and then back to the minimum.
Spread Spectrum Modulation can be applied as either
“center spread” or “down spread”. During center spread
modulation, the deviation from the target frequency is
equal in the positive and negative directions. The
effective average frequency is equal to the target
frequency. In applications where the clock is driving a
component with a maximum frequency rating, down
spread should be applied. In this case, the maximum
frequency, including modulation, is the target
frequency. The effective average frequency is less than
the target frequency.
The ICS345 operates in both center spread and down
spread modes. For center spread, the frequency can
be modulated between +/- 0.125% to +/-2.0%. For
down spread, the frequency can be modulated
between -0.25% to -4.0%.
Both output frequency banks will utilize identical spread
spectrum percentage deviations and modulation rates,
if a common VCO frequency can be identified.
Spread Spectrum Modulation Rate
The spread spectrum modulation frequency applied to
the output clock frequency may occur at a variety of
rates. For applications requiring the driving of
“down-circuit” PLLs, Zero Delay Buffers, or those
adhering to PCI standards, the spread spectrum
modulation rate should be set to 30-33 kHz. For other
applications, a 120 kHz modulation option is available.
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS345. These ratings, which
are standard values for ICS 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.
Parameter
Supply Voltage, VDD
Inputs
Clock Outputs
Storage Temperature
Soldering Temperature
Junction Temperature
Condition
Referenced to GND
Referenced to GND
Referenced to GND
Max 10 seconds
Min.
-0.5
-0.5
-65
Typ.
Max.
7
VDD+0.5
VDD+0.5
150
260
125
Units
V
V
V
°C
°C
°C
MDS 345 E
Integrated Circuit Systems, Inc.
●
4
525 Race Street, San Jose, CA 95126
●
Revision 011205
tel (408) 297-1201
●
www.icst.com
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
