How to select the right eSATA connector and cable

How to select the right eSATA connector and cable
How to select the right eSATA connector and cable
By COMAX Technology Inc.
External SATA (or called eSATA) is popular discussion between developers and
manufacturers recently. This includes single disk external drive and multi-disk external
storage/backup with RAID/Port multiplier features. New generation STB (Set top box) and MB
(motherboard) product releases have also added eSATA connectors on board. This indicates the
demand in eSATA external storage market is on the rise
Many developers assume just by adding the shielding in the internal SATA connector, it will
enable the drive for outside use. This thinking involves certain risks. In particular for the
important external storage equipment, eSATA must resolve the following issues:
1.
To prevent ESD (Electro-static Discharge) damage during connector plugging.
2.
To comply with EMI (Electro-magnetic Interference) limits per FCC and CE regulations.
3.
To withstand the more frequent insert/removal cycles (called Durability) by the users.
Without going through (SATA-IO) test standards, some hidden issues in matching and
operation will be expected. It is unclear whether durability cycles are sufficient; electrical high
speed performance is reliable when used in the exterior environment.
The selection of proper eSATA connector and cable during the design-in is becoming
critical. It is essential to consider both the eSATA connector and cable together. The products
themselves should meet SATA-IO specified requirements. In addition, it makes sense to select a
vendor with good experience in both design and volume production. Choosing a vendor who
can do self certification for both components and end products, who works together with
SATA-IO from concept, and in addition who provides the eSATA measurement test fixtures are
the hints to smoothly design-in eSATA products.
Unfortunately, some eSATA cable connectors in the market today are questionable in
tolerance design, mated impedance control, or even the cable connector shielding. If these
products are engaged in interoperability test, there will be problems in system transmission, or
slower speed that degrades eSATA performances. It may even be possible to cause system
hanging in normal operation. These are not what users want to see.
What is different on eSATA connectors?
1. No “L” shape key to prevent unshielded internal cable to plug-in.
2. Anti-USB key feature on both side of housing to prevent USB cable to plug-in.
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3. Insertion depth increased to 6.6mm to prevent ESD damage.
4. Added metallic housing with 2 springs contact feature on top and bottom of front edge
to reduce EMI.
5. Built spring retention feature on the top and bottom of shell to increase the durability
to 2500 cycles and sustain the insertion force within 40N and removal force over 10N.
6. Built hold down feature on metallic housing to mount on PCB robustly.
What is different on eSATA cables?
1. Built lead-in feature on both side of housing of cable end connector for easy plugging
into connector of PCB end.
2. Added metallic housing with 2 spring contact feature on top and bottom of front edge
to prevent ESD damage.
3. Built 2 square holes feature on top and bottom of metal shell to mate with connector of
PCB end to increase the retention force and durability.
4. Fully shielded around the cable to reduce EMI. The outer shielding for chassis ground is
separate from signal ground.
5. Used stranded copper wire to make the cable flexible and to extend longer cable length
up to 2 meters.
6. Met electrical Gen1m/Gen2m phy requirement, with hot plugging support but without
power support.
7. The external cable electrical parameter requirements are different from internal
requirements as shown below:
A.
Maximum insertion loss (10-4500MHz) from 6db to 8db.
B.
Maximum rise time (35ps input) from 85ps to 150ps.
C.
Maximum intra-pair skew from 10ps to 20ps.
About the ESD issue, please refer to the following detail information:
http://www.sata-io.org/docs/ESD_control_for_eSATA_a02-RC-1.pdf
What do you need to consider when you select the connector?
There are 5 basic types connector for your choice.
1. R/A SMT
2. R/A SMT Reverse
3. R/A DIP
4. Vertical SMT
5. Vertical DIP
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Before you select the R/A SMT type connector, please check the pin assignment of the chip
that you selected. R/A SMT reverse type is friendly design for IC and PCB layout that prevents
the cross traces in high speed transfer situation. The post size and location of R/A SMT reverse
type is different with R/A SMT type to prevent mistake when you use two types of connector in
your manufacturing line.
Don’t miss the spring in front edge to contact the chassis for grounding. And don’t miss the
retention spring to mate with spring hole of cable connector for retention.
What do you need to consider when you select the cable?
Don’t use cable without shielding or ineffective shielding. The shielding needs to contact
with shell of cable connector well and it will be helpful to reduce EMI and prevent ESD.
Don’t forget to check the mated connector impedance, especially when the cable length is
over 1 meter long. That will be the key issue on high speed. The cable conductor affects the
energy loss. Don’t use thinner conductor cable for the length of 1 meter and above.
The rise-time and skew will affect the jitter. Don’t miss to check it.
What else do you need to consider when you adopt the connector and cable?
Don’t miss the compliance test report when you adopt the connector and cable in you
product. It needs NA (Network Analyzer) and TDR (Time Domain Reflectometer) to do
measurements frequently. Not only the equipments but also the quality of test fixture should be
considered to get accurate result.
About Comax Technology Inc.
Comax Technology Inc. has been with SATA working group for over 6 years and is experienced
in defining eSATA specification and product marketing for the last 3 years from eSATA inception.
For more Comax information, please check out the 2006 new look of our website at
http://www.comaxtech.com
October 3, 2006
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