Electrical Specifications
2.4.1
Phase Lock Loop (PLL) Power and Filter
VCCA and VCCIOPLL are power sources required by the PLL clock generators on the Celeron D
processor silicon. Since these PLLs are analog, they require low noise power supplies for minimum
jitter. Jitter is detrimental to the system: it degrades external I/O timings as well as internal core
timings (i.e., maximum frequency). To prevent this degradation, these supplies must be low pass
filtered from VCC
.
The AC low-pass requirements, with input at VCC are as follows:
• < 0.2 dB gain in pass band
• < 0.5 dB attenuation in pass band < 1 Hz
• > 34 dB attenuation from 1 MHz to 66 MHz
• > 28 dB attenuation from 66 MHz to core frequency
The filter requirements are illustrated in Figure 2-1.
.
Figure 2-1. Phase Lock Loop (PLL) Filter Requirements
0.2 dB
0 dB
–0.5 dB
Forbidden
Zone
Forbidden
Zone
–28 dB
–34 dB
DC
1 Hz
Passband
fpeak
1 MHz
66 MHz
fcore
High
Frequency
Band
NOTES:
1. Diagram not to scale.
2. No specification exists for frequencies beyond fcore (core frequency).
3. fpeak, if existent, should be less than 0.05 MHz.
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Datasheet
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