AN11001
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Application note
Rev. 1 — 7 March 2011
9 of 17
NXP Semiconductors
AN11001
CBTL02042A switching application for mSATA, PCIe Mini-Card
•
AC coupling capacitors should be placed close to the connector for optimal signal
quality. Capacitors must be of type X7R with values of 10 nF
15 % and body size
0402.
•
Maximum of 6 inches (15.24 cm) trace length from host controller to SATA connector
is strongly suggested.
4.3 Topology with CBTL02042A as a switch for Mini-Card/mSATA
CBTL02042A, like other high-speed switches, introduces certain amount of signal loss at
different frequencies. Without any switch on a PCB trace, the PCB trace itself introduces
some loss as well. Although the CBTL02042A can operate up to 7 Gbit/s, this particular
application mandates the operating speed of mSATA up to 3 Gbit/s (SATA Gen 2), and
PCIe on the Mini-Card up to 2.7 Gbit/s (PCIe Gen1). Hence, the critical signal frequency
we will be focusing on is 1.5 GHz. Typically, a signal loss of 0.25 dB exists for every 1 inch
(2.54 cm) of PCB trace on FR4 material at frequency of 1.5 GHz. At this frequency,
CBTL02042A exhibits signal loss of less than 1 dB, or translating to 3 inches (7.62 cm) to
4 inches (10.16 cm) of PCB trace. Keep this in mind, traces length of PCIe and SATA
signals will need to be reduced by 3 inches (7.62 cm) to 4 inches (10.16 cm) when
CBTL02042A is used to select either PCIe or SATA signals. Effectively, with
CBTL02042A, the maximum trace length reduces from 10 inches (25.4 cm) to 7 inches
(17.78 cm) for PCIe signals, and from 6 inches (15.24 cm) to 3 inches (7.62 cm) for SATA
signals.
The topology of PCIe and SATA signals going to Mini-Card/mSATA connector is shown in
. Note that the CBTL02042A should be placed close to the Mini-Card/mSATA
connector, with AC coupling capacitors placed on the side that is close to the host
controllers, but adjacent to CBTL02042A. PCIe’s RX signals (PERp0, PERn0) to the host
controller do not require AC coupling capacitors on the motherboard because they are
placed on the Mini-Card.
Fig 5.
Mini-Card/mSATA maximum trace length with CBTL02042A in place
019aaa991
PCIe HOST
CONTROLLER
CBTL
02042A
SATA HOST
CONTROLLER
Mini-Card/mSA
T
A
CONNECT
OR
2 inches to 3 inches
(5.08 cm to 7.62 cm)
maximum
6 inches to 7 inches
(15.24 cm to 17.78 cm)
maximum
RX
TX
RX
TX
