LTC4279
Single Port PoE/PoE+/
LTPoE++ PSE Controller
FEATURES
nn Compliant with IEEE 802.3at Type 1 and 2
nn Supports LTPoE++® Up to 90W
nn Supports Dual-Signature PDs
nn Fully Autonomous Operation without Microcontroller
nn Very Low Power Dissipation
– 0.1Ω Sense Resistance
– Low RDS(ON) External MOSFET
nn Very High Reliability 4-Point PD Detection
– 2-Point Forced Voltage and Forced Current
nn Robust Short-Circuit Protection
nn Cable Surge Protected ±80V OUT Pin
nn Classification Dependent ICUT and ILIM Current
Thresholds
nn Supports 2-Pair and 4-Pair Output Power
nn UltraPWR Mode Supports Custom PDs Up to 123W
nn Pin-Selectable Detection Backoff Timer for Midspans
nn Pin Programmable Legacy PD Detection
nn Pin Programmable Maximum Power Mode
nn Status LED Pin
nn Available in 20-Pin QFN and 16-Pin SO Packages
APPLICATIONS
nn PoE PSE Endpoints (Switch/Router)
nn PoE Midspan Power Injectors
nn Power Forwarders
nn Femto Cells
nn Security Systems
DESCRIPTION
The LTC®4279 is an autonomous single port power sourc-
ing equipment (PSE) controller designed for use in IEEE
802.3at Type 1, Type 2 and LTPoE++ compliant Power
over Ethernet (PoE) systems. The LTC4279 provides fully
autonomous IEEE 802.3 and LTPoE++ compliant operation
without a microcontroller. The LTC4279 simplifies PSE
implementation, requiring only a single supply and a small
number of passive support components.
The LTC4279 delivers lowest-in-industry heat dissipation
by utilizing a low-RDS(ON) external MOSFET and a 0.1Ω
sense resistor, eliminating the need for expensive heat
sinks and increasing efficiency.
PD discovery uses a proprietary dual-mode 4-point detec-
tion mechanism ensuring excellent immunity from false
PD detection. Midspan PSEs are supported with physical
layer classification and a 2.5 second backoff timer.
Legacy and custom PDs are supported with pin-selectable
LEGACY and UltraPWR modes. LEGACY mode detects
and powers pre-IEEE specification PDs. UltraPWR mode
aggressively turns on and powers custom PDs requiring
high inrush and/or operational currents.
L, LT, LTC, LTM, Linear Technology, the Linear logo and LTPoE++ are registered trademarks of
Analog Devices, Inc. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
CBULK
VEE
10Ω
TVSBULK
1µF
100V
X7R
SMAJ58A RPM
LED
RESET
AGND
LTC4279
PWRMODE
MID
LEGACY
DUALPD
VEE
OUT
GATE
SENSE
VSSK
RGATE
0.22µF
100V S1B
X7R
0.1Ω
4279 TA01
MAXIMUM PD INPUT POWER
+ Type 1 (13W)
PORT
–
Type 2 (25.5W)
LTPoE++ 38.7W
LTPoE++ 52.7W
LTPoE++ 70W
LTPoE++ 90W
UltraPWR – (Up to 123W*)
*Depending on VPSE
For more information www.linear.com/LTC4279
RPM (±1%)
2.37k
3.32k
4.64k
5.90k
7.87k
10.0k
13.0k
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