Intel 1.80 GHz RH80532NC033256 データシート
製品コード
RH80532NC033256
Mobile Intel
®
Celeron
®
Processor (0.13 µ) in
Micro-FCBGA and Micro-FCPGA Packages Datasheet
98 Datasheet
298517-006
Table 58. PLL Filter Resistor Recommendations
Resistor Part
Number
Value Tolerance
Power
R1 Various
1
Ω
10% 1/16W
To satisfy damping requirements, total series resistance in the filter (from V
CCT
to the top plate of the
capacitor) must be at least 0.35
Ω. This resistor can be in the form of a discrete component, or routing,
or both. For example, if the picked inductor has minimum DCR of 0.25
Ω, then a routing resistance of
at least 0.10
Ω is required. Be careful not to exceed the maximum resistance rule (2 Ω). For example, if
using discrete R1, the maximum DCR of the L should be less than 2.0 - 1.1 = 0.9
Ω, which precludes
using L2 and possibly L1.
Other routing requirements include:
• The capacitor should be close to the PLL1 and PLL2 pins, with less than 0.1 Ω per route (These
routes do not count towards the minimum damping resistance requirement).
• The PLL2 route should be parallel and next to the PLL1 route (minimize loop area).
• The inductor should be close to the capacitor; any routing resistance should be inserted between
• The inductor should be close to the capacitor; any routing resistance should be inserted between
VCCT and the inductor.
• Any discrete resistor should be inserted between V
CCT
and the inductor.
A4. Comments
• A magnetically shielded inductor protects the circuit from picking up external flux noise. This
should provide better timing margins than with an unshielded inductor.
• A discrete or routed resistor is required because the LC filter by nature has an under-damped
response, which can cause resonance at the LC pole. Noise amplification at this band, although
not in the PLL-sensitive spectrum, could cause a fatal headroom reduction for analog circuitry.
The resistor serves to dampen the response. Systems with tight space constraints should consider a
discrete resistor to provide the required damping resistance. Too large of a damping resistance can
cause a large IR drop, which means less analog headroom and lower frequency.
not in the PLL-sensitive spectrum, could cause a fatal headroom reduction for analog circuitry.
The resistor serves to dampen the response. Systems with tight space constraints should consider a
discrete resistor to provide the required damping resistance. Too large of a damping resistance can
cause a large IR drop, which means less analog headroom and lower frequency.
• Ceramic capacitors have very high self-resonance frequencies, but they are not available in large
capacitance values. A high self-resonant frequency coupled with low ESL/ESR is crucial for
sufficient rejection in the PLL and high frequency band. The recommended tantalum capacitors
have acceptably low ESR and ESL.
sufficient rejection in the PLL and high frequency band. The recommended tantalum capacitors
have acceptably low ESR and ESL.
• The capacitor must be close to the PLL1 and PLL2 pins; otherwise the value of the low ESR
tantalum capacitor is wasted. Note the distance constraint should be translated from the 0.1-
Ω
requirement.