FSB Design Guidelines
R
Intel
®
855PM Chipset Platform Design Guide
55
4.1.4.1.4.
Topology 2A: Open Drain (OD) Signal Driven by Intel 82801DBM ICH4-M –
PWRGOOD
The Topology 2A OD signal PWRGOOD driven by the Intel 82801DBM ICH4-M (processor CMOS
signal input) should adhere to the following routing and layout recommendations. Table 11 lists the
recommended routing requirements for the PWRGOOD signal of the processor. The routing guidelines
allows the signal to be routed as either micro-strip or strip-lines using 55
± 15% characteristic trace
impedance. The pull-up voltage for termination resistor Rtt is V
CCP
(1.05 V). Note that the Intel ICH4-
M’s CPUPWRGD signal should be routed point-to-point to the processor’s PWRGOOD signal. The
routing from the processor’s PWRGOOD pin should fork out to both to the termination resistor, Rtt, and
the ICH4-M. Segments L1 and L2 from Figure 19 should not T-split from a trace from the processor
pin.
Figure 19. Routing Illustration for Topology 2A
Intel
Pentium M
processor
Intel
ICH4-M
VCCP
L2
Rtt
L1
Table 11. Layout Recommendations for Topology 2A
L1
L2
Rtt
Transmission Line Type
0.5” – 12.0”
0” – 3.0”
330
± 5%
Micro-strip
0.5” – 12.0”
0” – 3.0”
330
±5%
Strip-line
Содержание 855PM
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