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© 2007 Semtech Corp.
www.semtech.com
PRELIMINARY
PROTECTION PRODUCTS
RClamp0522T
RClamp0524T
Figure 2 - TDR Measurement with 200ps risetime
using Semtech Evaluation Board
A B
X-axis
1.905 2.081
(nsec)
Y-axis
101.0 107.0
(Ohm)
Figure 3 - TDR Measurement with 100ps risetime
using Semtech Evaluation Board
B
A
B
A
B
A
B
A
A B
X-axis
1.80 2.076
(nsec)
Y-axis
96 108.0
(Ohm)
Note: Measurements were taken on SLP HDMI EVAL Rev C Board that has 100Ω
differential traces impedance throughout (No trace Compensation).
Applications Information
Protecting MDDI Ports with RClamp0524T and
RClamp0522T
The small package size and low capacitance of the
RClamp0522T and RClamp0524T make them ideal for
high-speed lines in portable applications. One such
application is the protection of MDDI ports in cellular
phones. MDDI is a serial data interface operating at
480Mb/s per line pair. The lines are scalable for
increased speed and display resolution. A MDDI port
protection example is shown in Figure 5. The
RClamp0524T is used to protect two differential line
pairs while an RClamp0522T is used to protect the
MDDI strobe lines. Note that devices are used on
both the main board and LCD side of the MDDI port.
Devices on the main board are needed to protect the
MDDI controller in the Baseband processor and
devices on the LCD board to protect MDDI controller in
LCD module. A single line TVS such as the
uClamp0501P is used to protect the MDDI power line.
The protection devices should be placed close to the
connector of each board. Traces are routed directly
through each device, minimizing parasitic inductance.
Connections to the ground plane should be made with
multiple micro vias when possible.
Specification (CTS). In each case, the device meets
the HDMI CTS requirement of 100 Ohm ±15% with
plenty of margin.
For signal integrity purposes, the best results will be
obtained by using the RClamp0524T to protect the
high-speed differential pairs. This is because the
device is designed such that the data lines from the
connector line up with the I/O pins of the device
without altering the trace routing. The RClamp0504P
may be used to protect the remaining lines (I2C, CEC,
and hot plug).
Layout Guidelines for Optimum ESD Protection
Good circuit board layout is critical not only for signal
integrity, but also for effective suppression of ESD in-
duced transients. For optimum ESD protection, the
following guidelines are recommended:
z Place the device as close to the connector as pos-
sible. This practice restricts ESD coupling into
adjacent traces and reduces parasitic inductance.
z The ESD transient return path to ground should be
kept as short as possible. Whenever possible, use
multiple micro vias connected directly from the device
ground pad to the ground plane.
z Avoid running critical signals near board edges.
