XRS10L620 Datasheet, PDF (44/49 Pages) Exar Corporation – PCI-X to 2-SATA/1-PATA Host Controller

The PRD table format is as below :
DW# Bit#
Description
DW0 31:00 Data Base Address(Low)
DW1 31:00 Data Base Address(High)
DW2 31:00 Reserved
31 End of Transfer(EOT): indicates the last PRD of the whole list
DW3 30:17 Reserved
16:00 Byte count of this PRD, 64KB(10000h) maximum
XRS10L620 Rev 1.00
8. PCB High-Speed Layout Design Guidelines
1. High speed differential signals (TX+ & TX-, RX+ & RX-) should be routed as micro-strips on
layer 1. No via or stubs for these critical traces. Differential pairs trace length should be identical.
2. Impedance should be controlled at 100 ohms +- 5% for differential pair, and 50 ohms +- 10% for single ended.
3. Keep the trace length of differential pairs as short as possible. Avoid sharp turns, use rounded corner. It is highly
recommended to keep them within two inches long. Make sure no other signals are routed near these critical traces. Keep
a good separation between these differential pairs and other signals, minimum of 50 mils clearance is recommended.
4. Recommended board stack-up and routing example:
Material: FR4, with Dielectric constant of 4.2, and total thickness 62 mils.
Layer 1, Signal
FR4 Prepreg
Layer 2, Ground
FR4 Prepreg
Layer 3, Power
FR4 Prepreg
Layer 4, Signal
Thickness
0.5 oz
4 mils
1 oz
47 mils
1 oz
4 mils
0.5 oz
Diff Pair Width
8 mils
Diff Pair Spacing
12 mils
5. When the differential layout cannot be achieved, e.g. around the connector area, neck-down technique to maintain
single-ended 50 ohms is highly recommended.
6. For other signals where VIA is unavoidable, anti-pad is required to provide adequate clearance.
7. Place AC coupled 10nF capacitors as close as possible to the connector end, minimize the soldering pad area. The layout
of capacitors can be combined with SATA connector to minimize impedance discontinuities. Use smaller footprint like
0402 to minimize package parasitic.
8. Use surface mount SATA connector, avoid over-soldering. Minimize the width of RX and TX soldering pads for SATA
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1/20/2009