5© 2010 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
RClamp3304NA
Circuit Diagram
Applications Information
Pin 5
Pin 1 Pin 9 Pin 3 Pin 7
Gnd
Pin ConfPin Conf
Pin ConfPin Conf
Pin Conf
iguration (Tiguration (T
iguration (Tiguration (T
iguration (T
op Side Vieop Side Vie
op Side Vieop Side Vie
op Side Vie
w)w)
w)w)
w)
2
1
3
6
8
4
5
GND
7
9
10
niPnoitacifitnedI
9,7,3,1seniLtuptuO/tupnI
01,8,6,4,2tcennoCoN
5
tcennoCoN
)ylppusCDaotnipsihttcennoctonoD(
ba
TretneCdnuorG
Device Connection Options for Protection of Four
High-Speed Data Lines
These devices are designed to protect low voltage data
lines operating at 3.3 volts. 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, 3, 7 and 9. The
center pin should be connected directly to a ground
plane. The path length is kept as short as possible to
minimize parasitic inductance. Pins 2, 4, 6, 8, and 10
are not connected.
Note that pin 5 is connected internally to the cathode
of the low voltage TVS. It is not recommended that
these pins be directly connected to a DC source
greater than the snap-back voltage (V
SB
) as the device
can latch on as described below.
EPD TVS Characteristics
These devices are constructed using Semtech’s
proprietary EPD technology. By utilizing the EPD tech-
nology, the RClamp3304NA can effectively operate at
3.3V while maintaining excellent electrical characteris-
tics.
The EPD TVS employs a complex nppn structure in
contrast to the pn structure normally found in tradi-
tional silicon-avalanche TVS diodes. Since the EPD
TVS devices use a 4-layer structure, they exhibit a
slightly different IV characteristic curve when compared
to conventional devices. During normal operation, the
device represents a high-impedance to the circuit up to
the device working voltage (V
RWM
). During an ESD
event, the device will begin to conduct and will enter a
low impedance state when the punch through voltage
(V
PT
) is exceeded. Unlike a conventional device, the low
voltage TVS will exhibit a slight negative resistance
characteristic as it conducts current. This characteris-
tic aids in lowering the clamping voltage of the device,
but must be considered in applications where DC
voltages are present.
When the TVS is conducting current, it will exhibit a
slight “snap-back” or negative resistance
characteristics due to its structure. This point is
defined on the curve by the snap-back voltage (V
SB
)
and snap-back current (I
SB
). To return to a non-
conducting state, the current through the device must
fall below the I
SB
(approximately <50mA) and the
voltage must fall below the V
SB
(normally 2.8 volts for a
3.3V device). If a 3.3V TVS is connected to 3.3V DC
source, it will never fall below the snap-back voltage of
2.8V and will therefore stay in a conducting state.
