PCS5P23Z05C Datasheet, PDF (3/14 Pages) PulseCore Semiconductor – Multiple Output Timing-Safe™ Peak EMI reduction IC

May 2007
rev 0.1
Spread Spectrum Frequency Generation
The clocks in digital systems are typically square waves
with a 50% duty cycle and as frequencies increase the
edge rates also get faster. Analysis shows that a square
wave is composed of fundamental frequency and
harmonics. The fundamental frequency and harmonics
generate the energy peaks that become the source of
EMI. Regulatory agencies test electronic equipment by
measuring the amount of peak energy radiated from the
equipment. In fact, the peak level allowed decreases as
the frequency increases. The standard methods of
Timing-Safe™ technology
Timing-Safe™ technology is the ability to modulate a
clock source with Spread Spectrum technology and
maintain synchronization with any associated data path.
Pin Configuration
PCS5P23Z05C
PCS5P23Z09C
reducing EMI are to use shielding, filtering, multi-layer
PCBs etc. These methods are expensive. Spread
spectrum clocking reduces the peak energy by reducing
the Q factor of the clock. This is done by slowly
modulating the clock frequency. The PCS5P23Z05C/09C
uses the center modulation spread spectrum technique in
which the modulated output frequency varies above and
below the reference frequency with a specified
modulation rate. With center modulation, the average
frequency is same as the unmodulated frequency and
there is no performance degradation
REF ¹
8 CLKOUT
CLK1 ²
CLK2 3
7
PCS5P23Z05C
6
CLK4
V_DD
GND 4
5 CLK3
REF 1
CLKA1 ₂
CLKA2 3
V_DD ⁴
GND ₅
CLKB1 6
CLKB2 7
S2 8
PCS5P23Z09C
16 CLKOUT
15 _CLKA4
14 _CLKA3
13 _VDD
12 _GND
11 CLKB4
10 CLKB3
9 S1
Zero Cycle Slip Peak EMI Reduction IC
Notice: The information in this document is subject to change without notice.
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