SLVU2.8 Datasheet, PDF (6/10 Pages) Semtech Corporation – Low Voltage EPD TVS Diode For ESD and Latch-Up Protection

SLVU2.8
PROTECTION PRODUCTS
Applications Information (continued)
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.
The IV characteristic curve of the EPD device is shown
in Figure 1. The device represents a high impedance
to the circuit up to the working voltage (V ). During a
RWM
transient event, the device will begin to conduct as it is
biased in the reverse direction. When the punch-
through voltage (V ) is exceeded, the device enters a
PT
low impedance state, diverting the transient current
away from the protected circuit. When the device is
conducting current, it will exhibit a slight “snap-back” or
negative resistance characteristic due to its structure.
This must be considered when connecting the device
to a power supply rail. To return to a non-conducting
state, the current through the device must fall below
the snap-back current (approximately < 50mA).
IPP
VBRR
I_SB
IPT
I_R
VRWM VSB VPT VC
SLVU2.8
Laser Diode Protection
Circuit Board Layout Recommendations for Suppres-
sion of ESD.
Good circuit board layout is critical for the suppression
of ESD induced transients. The following guidelines are
recommended:
z Place the SLVU2.8 near the input terminals or
connectors to restrict transient coupling.
z Minimize the path length between the TVS and the
protected line.
z Minimize all conductive loops including power and
ground loops.
z The ESD transient return path to ground should be
kept as short as possible.
z Never run critical signals near board edges.
z Use ground planes whenever possible.
I_BRR
EPD TVS IV Characteristic Curve
Matte Tin Lead Finish
Matte tin has become the industry standard lead-free
replacement for SnPb lead finishes. A matte tin finish
is composed of 100% tin solder with large grains.
Since the solder volume on the leads is small com-
pared to the solder paste volume that is placed on the
land pattern of the PCB, the reflow profile will be
determined by the requirements of the solder paste.
Therefore, these devices are compatible with both
lead-free and SnPb assembly techniques. In addition,
unlike other lead-free compositions, matte tin does not
have any added alloys that can cause degradation of
the solder joint.
© 2008 Semtech Corp.
6
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