5
© 2008 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
uClamp3305P
Device Connection Options
The μClamp3305P is designed to protect 5 signal lines
with an operating voltage of 0 to 3.3V. It will present a
high impedance to the protected line up to 3.3 volts. It
will “turn on” when the line voltage exceeds 3.5 volts.
The device is unidirectional and may be used on lines
where the signal polarity is above ground.
Pin 1,3,4,5,6 are connected to I/O signals. The center
tab is connected to system ground. Pin 2 should be left
open or not connected. All signal lines and ground
should be made with the lowest impedance and
inductance path as possible. This will improve signal
quality of the lines and keep the clamping voltage as low
as possible during a fast transient.
Due to the “snap-back” characteristics of the low
voltage TVS, it is not recommended that the I/O line be
directly connected to a DC source greater than snap-
back votlage (V
SB
) as the device can latch on.
EPD TVS
Characteristics
These devices are constructed using Semtech’s
proprietary EPD technology. The structure of the EPD
TVS is vastly different from the traditional pn-junction
devices. At voltages below 5V, high leakage current
and junction capacitance render conventional ava-
lanche technology impractical for most applications.
However, by utilizing the EPD technology, these devices
can effectively operate at 3.3V while maintaining
excellent electrical characteristics.
The EPD TVS employs a complex nppn structure in
contrast to the pn structure normally found in tradi-
tional silicon-avalanche TVS diodes. The EPD mecha-
nism is achieved by engineering the center region of
the device such that the reverse biased junction does
not avalanche, but will “punch-through” to a conduct-
ing state. This structure results in a device with supe-
rior DC electrical parameters at low voltages while
maintaining the capability to absorb high transient
currents.
Applications Information
Figure 1 - Circuit Diagram
IPP
I
SB
I
PT
I
R
V
RWM
VV
PT
V
C
V
F
I
F
SB
Figure 3 - EPD TVS IV Characteristic Curve
Figure 2 - Layout Example
Center Tab (GND)
1
3
4
5
6
