5
© 2008 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
RClamp0502A
Applications Information
Device Connection Options for Protection of Two
High-Speed Data Lines
This device is designed to protect data lines by
clamping them to a fixed reference. When the voltage
on the protected line exceeds the reference voltage
the steering diodes are forward biased, conducting the
transient current away from the sensitive circuitry.
Data lines are connected at pins 1 & 6 and pins 3 & 4.
Pins 5 and 2 can be connected to ground or Vcc based
on application and location of those connections. The
connection to ground should be made directly to a
ground plane. The path length should also be kept as
short as possible to minimize parasitic inductance.
Figure 1 shows the layout configuration to send data
input at pins 6 and 4 and output at pins 1 and 3.
This device is designed for ease of PCB layout by
allowing the traces run straight through the device.
Figure 2 shows the proper way to design the PCB
board trace in order to use the flow through layout for
two line pairs. The solid line represents the PCB trace.
Note the PCB traces are used to connect the pin pairs
for each I/O (pin 1 to pin 6 and pins 3 to pin 4). For
example, I/O 1 enters at pin 6 and exits at pin 1 and
the PCB trace connects pins 6 and 1 together. This is
also true for I/O 2. The negative reference (Gnd) is
connected at pin 2. The positive reference is
connected at pin 5.
Universal Serial Bus ESD Protection
The RClamp0502A may also be used to protect both
upstream and downstream USB ports on monitors,
computers, peripherals or portable systems. Each
device will protect up to one USB port (Figure 3). When
the voltage on the data lines exceed the bus voltage
(plus one diode drop), the internal rectifiers are
forward biased conducting the transient current away
from the protected controller chip. The TVS diode
directs the surge to ground. The TVS diode also acts
to suppress ESD strikes directly on the voltage bus.
Thus, both power and data pins are protected with a
single device.
Figure 1. Protection of Two Data Lines
and One Power Supply Line
Figure 2. Flow Through Layout for
Two Data Lines and one Power Line
Figure 3. USB 2.0 (up to 480Mbps)
Upstream or Downstream Port Protection
2
1
34
5
6
Vcc
Gnd
D+
D-
D+
to protected Circuit
D-
to protected Circuit
