Linear Technology DC1366B Manual page 6

DEMO MANUAL DC1366B
operation
Up to sixteen DC1366B can be controlled by a single I
master. Remember to set each board to a different I
address using the DIP switch.
The DC590 cannot supply enough current on V
than five or six DC1366B boards; an external V
supply is recommended if more than five DC1366B boards
are connected together.
If a large number of DC1366B boards are connected to a
single V supply, be aware that banana patch cords are
EE
only rated for approximately 14A. To avoid exceeding the
ampacity of the patch cords, the boards should be con-
nected in a star configuration rather than connecting the
boards in a chain.
QuikEval GUI Software
The QuikEval GUI application software is a powerful tool
for learning the LTC4266 registers. Also available is the
LTC4266NDASI software interface data sheet that provides
further details on these registers.
Surge Protection
Ethernet ports can be subject to significant cable surge
events. To keep PoE voltages below a safe level and protect
the application against damage, protection components
are required at the main supply, at the LTC4266 supply
pins and at each port.
6
2
C Bulk transient voltage suppression devices and bulk
2
C capacitance are required across the main PoE supply
and should be sized to accommodate system level surge
requirements. The DC1366B diode D18 and capacitor C2
for more
DD
are example components for this protection at the main
power
DD
PoE supply.
Each LTC4266 requires a 10Ω, 0805 resistor (R35) in se-
ries from supply AGND to the LTC4266 AGND pin. Across
the LTC4266 AGND pin and V
TVS (D1) and a 1μF, 100V bypass capacitor (C64). These
components must be placed close to the LTC4266 pins.
Each port requires a pair of S1B clamp diodes: one from
OUTn to supply AGND and one from OUTn to supply V
The diodes at the ports steer harmful surges into the supply
rails where they are absorbed by the surge suppressors
and the V
EE
must be low impedance.
Finally, the V
require additional surge protection. Components D23,
C16, R36, D2, and C65 demonstrate surge protection
for V to DGND. For a positive V
DD
V is +3.3V above AGND and DGND is tied to AGND, the
DD
DC1366B has place holders at D28 and C66 for a 64V TVS
and high voltage capacitance from V
pin are an SMAJ58A, 58V
EE
bypass capacitance. The layout of these paths
logic supply and logic pins may also
DD
configuration where
DD
DD
.
EE
to V .
EE
dc1366bf