Datasheet

6.0 DP83843 Application (Continued)
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6.3.1 ESD Protection
Typically, ESD precautions are predominantly in effect
when handling the devices or board before being installed
in a system. In those cases, strict handling procedures can
be implemented during the manufacturing process to
greatly reduce the occurrences of catastrophic ESD
events. After the system is assembled, internal compo-
nents are usually relatively immune from ESD events.
In the case of an installed Ethernet system however, the
network interface pins are still susceptible to external ESD
events. For example, a category 5 cable being dragged
across a carpet has the potential of developing a charge
well above the typical 2kV ESD rating of a semiconductor
device.
For applications where high reliability is required, it is rec-
ommended that additional ESD protection diodes be added
as shown below. There are numerous dual series con-
nected diode pairs that are available specifically for ESD
protection. The level of protection will vary dependent upon
the diode ratings. The primary parameter that affects the
level of ESD protection is peak forward surge current. Typi-
cal specifications for diodes intended for ESD protection
range from 500mA (Motorola BAV99LT1 single pair diodes)
to 12A (STM DA108S1 Quad pair array).
Since performance is dependent upon components used,
board impedance characteristics, and layout, the circuit
should be completely tested to ensure performance to the
required levels.
Figure 25. Typical DP83843 Network Interface with additional ESD protection
RJ-45
DP83843 10/100
TX±
RX±
Vcc
Vcc
Pin 1
Pin 2
Pin 3
Pin 6
Diodes placed on the
device side of the isola-
tion transformer