RClamp0522P
RClamp0524P
PROTECTION PRODUCTS
Applications Information
Design Recommendations for HDMI Protection
Adding external ESD protection to HDMI ports can be
challenging. First, ESD protection devices have an
inherent junction capacitance. However, adding even a
small amount of capacitance will cause the impedance
of the differential pair to drop. Second, large packages
and land pattern requirements cause discontinuities that
adversely affect signal integrity. The RClamp0524P and
RClamp0522P are specifically designed for protection
of high-speed interfaces such as HDMI. They present
<0.4pF capacitance between the pairs while being rated
to handle >±8kV ESD contact discharges (>±15kV air
discharge) as outlined in IEC 61000-4-2. Each device is
in a leadless SLP package that is less than 1.1mm wide.
They are designed such that the traces
fl
ow straight
through the device. The narrow package and
fl
ow-
through design reduces discontinuities and minimizes
impact on signal integrity. This becomes even more
critical as signal speeds increase.
Pin Configuration
Figure 1 is an example of how to route the high speed
differential traces through the RClamp0524P. The solid
line represents the PCB trace. The PCB traces are used
to connect the pin pairs for each line (pin 1 to pin 10, pin
2 to pin 9, pin 4 to pin 7, pin 5 to pin 6). For example,
line 1 enters at pin 1 and exits at Pin 10 and the PCB
trace connects pin 1 and 10 together. This is true for
lines connected at pins 2, 4, and 5 also. Ground is
connected at pins 3 and 8. One large ground pad should
be used in lieu of two separate pads. The same layout
rules apply for the RClamp0522P.
TDR Measurements for HDMI
The combination of low capacitance, small package, and
fl
ow-through design means it is possible to use these
devices to meet the HDMI impedance requirements of
100 Ohms ±15% without any PCB board modification.
Figures 2 and 3 show impedance test results for a TDR
risetime of 200ps and 100ps respectively, using a Sem-
tech
evaluation board with 100 Ohm traces throughout.
Measurements were taken using a TDR method as out-
lined in the HDMI Compliance Test Specification (CTS).
In each case, the device meets the HDMI CTS require-
PRELIMINARY
12
11
10
1
GND
GND
HDMI Connector
9
8
7
6
5
4
3
2
1
1
GND
GND
Figure 1. Flow through Layout Using RClamp0524P
2006 Semtech Corp.
6
www.semtech.com
SEMTECH [ SEMTECH CORPORATION ]
