SRDA3.3-4 Semtech, SRDA3.3-4 Datasheet - Page 4

• Manufacturer Part Number: SRDA3.3-4
• Description: TVS DIODE ARRAY, 500W, 3.3V, SOIC
• Manufacturer: Semtech

Specifications of SRDA3.3-4

• Diode Type: Low Capacitance
• Clamping Voltage Vc Max: 15V
• Operating Voltage: 3.3V
• Diode Case Style: SOIC
• No. Of Pins: 8
• Peak Reflow Compatible (260 C): No
• Capacitance, Cd: 8pF
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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 punch-through or “turn-on”
voltage of the TVS diode, the steering diodes are
forward biased, conducting the transient current away
from the sensitive circuitry.
Data lines are connected at pins 1, 4, 6 and 7. Pins 5
and 8 should be connected directly to a ground plane.
The path length is kept as short as possible to
minimize parasitic inductance.
Note that pins 2 and 3 are 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 votlage (V
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 SRDA3.3-4 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. 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
event, the device will begin to conduct and will enter a
low impedance state when the punch through voltage
(V
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 characteris-
tics due to its structure. This point is defined on the
curve by the snap-back voltage (V
PROTECTION PRODUCTS
PROTECTION PRODUCTS
© 2008 Semtech Corp.
Applications Information
PT
) is exceeded. Unlike a conventional device, the low
RWM
). During an ESD
SB
) and snap-back
SB
) as the device
4
Data Line Protection Using Internal TVS Diode as
Reference
current (I
current through the device must fall below the I
(approximately <50mA) and the voltage must fall below
the V
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.
SB
V
BRR
(normally 2.8 volts for a 3.3V device). If a 3.3V
SB
). To return to a non-conducting state, the
EPD TVS IV Characteristic Curve
I
I
I
I
SB
PT
PP
R
I
BRR
SRDA3.3-4
V
RWM
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V
SB
V
PT
V
C
SB