ltc4264cde-trpbf Linear Technology Corporation, ltc4264cde-trpbf Datasheet - Page 21

• Manufacturer Part Number: ltc4264cde-trpbf
• Description: High Power Pd Interface Controller With 750ma Current Limit
• Manufacturer: Linear Technology Corporation

V
LTC4264. If not used, tie SHDN to V
The load capacitor connected between GND and V
of the LTC4264 can store signifi cant energy when fully
charged. The design of a PD must ensure that this en-
ergy is not inadvertently dissipated in the LTC4264. The
polarity-protection diodes prevent an accidental short
on the cable from causing damage. However, if the V
pin is shorted to GND inside the PD while the capacitor
is charged, current will fl ow through the parasitic body
diode of the internal MOSFET and may cause permanent
damage to the LTC4264.
ELECTRO STATIC DISCHARGE AND SURGE
PROTECTION
The LTC4264 is specifi ed to operate with an absolute
maximum voltage of –90V and is designed to tolerate brief
over-voltage events. However, the pins that interface to the
outside world (primarily V
APPLICATIONS INFORMATION
OUT
, to avoid the possibility of leakage shutting down the
IN
and GND) can routinely see
IN
.
OUT
IN
peak voltages in excess of 10kV. To protect the LTC4264,
it is highly recommended that the SMAJ58A unidirectional
58V transient voltage suppressor be installed between the
diode bridge and the LTC4264 (D3 in Figure 4).
ISOLATION
The 802.3 standard requires Ethernet ports to be electrically
isolated from all other conductors that are user accessible.
This includes the metal chassis, other connectors and
any auxiliary power connection. For PDs, there are two
common methods to meet the isolation requirement. If
there will be any user accessible connection to the PD,
then an isolated DC/DC converter is necessary to meet
the isolation requirements. If user connections can be
avoided, then it is possible to meet the safety requirement
by completely enclosing the PD in an insulated housing.
In all PD applications, there should be no user accessible
electrical connections to the LTC4264 or support circuitry
other than the RJ-45 port.
LTC4264
21
4264f