ltc4270 Linear Technology Corporation, ltc4270 Datasheet - Page 28

• Manufacturer Part Number: ltc4270
• Description: 12-port Poe/poe+/ltpoe++ Pse Controller
• Manufacturer: Linear Technology Corporation

LTC4270/LTC4271
APPLICATIONS INFORMATION
ESD/Cable Discharge Protection
Ethernet ports can be subject to significant ESD events
when long data cables, each potentially charged to thou-
sands of volts, are plugged into the low impedance of the
RJ45 jack. To protect against damage, each port requires a
pair of clamp diodes; one to AGND and one to V
16). An additional surge suppressor is required for each
LTC4270 chip from V
steer harmful surges into the supply rails, where they are
absorbed by the surge suppressor and the V
capacitance. The surge suppressor has the additional
benefit of protecting the LTC4270 from transients on the
V
S1B diodes work well as port clamp diodes, and an
SMAJ58A or equivalent is recommended for the V
suppressor.
28
EE
supply.
EE
to AGND. The diodes at the ports
EE
EE
EE
(Figure
bypass
surge
LAYOUT GUIDELINES
Strict adherence to board layout, parts placement and
routing guidelines is critical for optimal current read-
ing accuracy, IEEE compliance, system robustness, and
thermal dissipation. Refer to the DC1682A Demo Board
as a layout reference. Contact LTC Applications to obtain
a full set of layout guidelines, example layouts and BOMs.
SMAJ58A
–54V
Figure 16. LTC4270 Discharge Protection
0.1μF
A
V
GND
EE
LTC4270
SENSEn
GATEn
OUTn
0.25Ω
0.22μF
42701 F17
S1B
S1B
PORTn
42701f