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40 Design Guide
Intel
®
31244 PCI-X to Serial ATA Controller
Printed Circuit Board (PCB) Methodology
• Jitter tolerance (TJ) must be >= 0.7 UI vs 0.62 UI of spec (@RCV pin)
• Slowest edge rate assumed
• Used only for GD31244 reads
• Read eye was guardbanded by 10 mV to allow for crosstalk
6.2.1 Backplane Topologies
This analysis looks at two backplane interconnection topologies. These two backplane topologies
are divided into the two categories for the read RX lines and write TX lines. These are shown in the
figures below. Figure 13a shows the GD31244 motherboard connecting through a connector to a
backplane with resistor attenuation for write topologies. Figure 13b shows the GD31244
motherboard connecting through a ribbon cable to a backplane for write topologies with resistor
attenuation. The resistor termination for Figure 13 is R1/R2 = 15 ohms/150 ohms 5% resistors
provided 50 ohm impedance.
The Figure 14a shows the read topology from the SATA hard drive to a connector to through the
backplane connector to the motherboard connecting to the GD31244 RX differential pins. In
Figure 14b shows the read topology from the SATA hard drive to a connector to through the
backplane connector through a ribbon cable to a motherboard connecting to the GD31244 RX
differential pins. Note that reads do not have the extra resistor termination.
This section provides an example target system topology for designing a GD31244-based Serial
ATA system. The target system implementation is based on one or more GD31244 chips mounted
on the mother board and a backplane supporting 4 to 16 hot-plug SATA drives.
In the proposed example topology covered in this section the backplane is configured mechanically
for either 3.5” x 1.0” or 2.5”x 0.75” form factor drives.
Figure 13. Write Backplane Topology
B0604-01
Package
Model
Intel
®
31224
MB
MB
SD
SD
BP
R1
R1
R2
BP
a. Write Backplane Topology
R1
R1
HDD
Package
Model
31224
MB
MB
SD
SD
BP
R1
Cable
R1
R2
BP
b. Write Backplane with Cable Topology
R1
R1
Connector
Connector
Connector
Connector
Connector
HDD