Intel CHIPSET 820E Manuale Utente Scaricare il pdf (Pagina 174)

Intel

820E Chipset

174 Design Guide

4.7. Unused Outputs

All unused clock outputs must be tied to ground through a series resistor that has approximately the

impedance of the output buffer (shown in the following table). These resistors are designed to terminate

unused outputs to eliminate EMI.

Table 60. Unused Output Termination

Buffer Name V

Range

(V)

Impedance

(Ω

ΩΩ

Ω)

If Unused Output

Termination to V

(Ω

ΩΩ

Ω)

CPU, CPU_Div2, IOAPIC 2.375 – 2.625 13.5 – 45 30

48 MHz, REF 3.135 – 3.465 20 – 60 40

PCI, 3V66 3.135 – 3.465 12 – 55 33

4.8. Decoupling Recommendation for CK133 and DRCG

Some CK133 vendors may integrate the XTAL_IN and XTAL_OUT frequency adjust capacitors.

However, pads should be placed on the board for these external capacitors for testing/debug.

To further reduce jitter and voltage supply noise, it is advisable to add a ferrite filter with 2 caps (10 µF

and 0.1 µF) on both the 2.5 V and 3.3 V planes, close to the clock devices. This applies to both DRCG

and CK133.

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Intel CHIPSET 820E Manuale Utente Pagina 174