LTC4274_1 Datasheet, PDF (1/28 Pages) Linear Technology – Single PoE+ PSE Controller High Capacitance Legacy Device Detection

LTC4274
Single PoE+ PSE Controller
FEATURES
n _{Compliant with IEEE 802.3at Type 1 and 2}
n _{0.34Ω Total Channel Resistance}
130mW/Port at 600mA
n _{Advanced Power Management}
8-Bit Programmable Current Limit (I_LIM)
7-Bit Programmable Overload Currents (I_CUT)
Fast Shutdown
14.5-Bit Port Current/Voltage Monitoring
2-Event Classification
n _{Very High Reliability 4-Point PD Detection:}
2-Point Forced Voltage
2-Point Forced Current
n _{High Capacitance Legacy Device Detection}
n _{LTC4259A-1 and LTC4266 SW Compatible}
n _{1MHz I}²_{C Compatible Serial Control Interface}
n _{Midspan Backoff Timer}
n _{Supports Proprietary Power Levels Above 25W}
n _{Available in 38-Pin 5mm × 7mm QFN Package}
APPLICATIONS
n _{PSE Switches/Routers}
n _{PSE Midspans}
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
DESCRIPTION
The LTC^®4274 is a single power sourcing equipment con-
troller designed for use in IEEE 802.3 Type 1 and Type 2
(high power) compliant Power over Ethernet systems.
External power MOSFETs enhance system reliability and
minimize channel resistance, cutting power dissipation and
eliminating the need for heatsinks even at Type 2 power
levels. External power components also allow use at very
high power levels while remaining otherwise compatible
with the IEEE standard. 80V-rated port pins provide robust
protection against external faults.
The LTC4274 includes advanced power management
features, including current and voltage readback and pro-
grammable I_CUT and I_LIM thresholds. Available C libraries
simplify software development; an optional AUTO pin mode
provides fully IEEE-compliant standalone operation with
no software required. Proprietary 4-point PD detection
circuitry minimizes false PD detection while supporting
legacy phone operation. Midspan operation is supported
with built-in 2-event classification and backoff timing.
Host communication is via a 1MHz I²C serial interface.
The LTC4274 is available in a 5mm × 7mm QFN package
that significantly reduces board space compared with
competing solutions.
TYPICAL APPLICATION
Complete Ethernet High Power Source
3.3V 0.1μF
SCL
INT
SDAIN
SDAOUT
AD0
AD1
AD2
AD3 _{DGND AGND}
SHDN
V_DD
LTC4274
V_EE SENSE GATE OUT
AUTO
MSD
RESET
MID
SMAJ58A
–54V
1μF
100V
S1B
S1B
–54V
0.22μF
100V
PORT
4274 TA01
4274fa
1