LTC4274 Datasheet, PDF (1/2 Pages) Linear Technology – Single IEEE 802.3at Power Over Ethernet Controller

LTC4274
Single IEEE 802.3at Power Over Ethernet Controller
FEATURES
■ _{Compliant with IEEE 802.3at Type 1 and 2}
■ _{Supports Proprietary Very High Power Up to 50W}
■ _{0.34Ω Total Channel Resistance}
130mW at 600mA
■ _{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
■ _{Very High Reliability 4-Point PD Detection:}
2-Point Forced Voltage
2-Point Forced Current
■ _{High Capacitance Legacy Device Detection}
■ _{LTC4259A-1 and LTC4266 SW Compatible}
■ _{1MHz I}²_{C Compatible Serial Control Interface}
■ _{Midspan Backoff Timer}
■ _{Available in 38-Pin 5mm × 7mm QFN Package}
APPLICATIONS
■ _{PoE PSE Switches/Routers}
■ _{PoE PSE Midspans}
DESCRIPTION
The LTC^®4274 is a single Power Sourcing Equipment (PSE)
controller designed for use in IEEE 802.3 Type 1 and Type 2
(high power) compliant Power over Ethernet (PoE) systems.
The LTC4274 is also a good choice for proprietary PoE PSE
systems, which may require more power than the new IEEE
802.3at standard allows. The LTC4274 can source up to 50W
while otherwise remaining compatible with IEEE 802.3at.
The LTC4274 delivers lowest-in-industry heat dissipation by
utilizing a low R_ON external MOSFET and a 0.25Ω sense resis-
tor, eliminating the need for expensive heat sinks. An external
MOSFET also provides a more robust solution compared to
an integrated MOSFET.
Advanced power management features include: selectable high
speed 9.5-bit (1kHz) or high resolution 14.5-bit current and
voltage readback, a 7-bit DAC for overcurrent threshold (I_CUT),
a unique nonlinear 8-bit programmable current limit (I_LIM) and
versatile quick shutdown. PD Discovery uses a proprietary dual-
mode 4-point detection mechanism ensuring the best immunity
from false PD detection. Midspan PSEs are supported with
2-event classification and a two second backoff timer. Legacy
high-capacitance device detection is available. The LTC4274
includes an I²C serial interface operable up to 1MHz.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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
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