dp83846a National Semiconductor Corporation, dp83846a Datasheet - Page 25

• Manufacturer Part Number: dp83846a
• Description: Dsphyter ? Single 10/100 Ethernet Transceiver
• Manufacturer: National Semiconductor Corporation

3.6 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 ESD rating of a semiconductor
device.
DP83846A 10/100
Figure 10. Typical DP83846A Network Interface with additional ESD protection
TX
RX
DIODES PLACED
ON THE DEVICE
SIDE OF THE
ISOLATION
TRANSFORMER
5V Vcc
5V Vcc
3.3V Vcc
25
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). The user should
also select diodes with low input capacitance to minimize
the effect on system performance.
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.
PIN 2
PIN 3
PIN 1
PIN 6
RJ-45
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