LT4275 Datasheet, PDF (1/12 Pages) Linear Technology – LTPoE++/PoE+/PoE PD Controller

Features
n _{IEEE 802.3af/at and LTPoE++™ Powered Device}
(PD) Controller
n _{LTPoE++ Supports Power Levels Up to 90W}
n _{LT4275A Supports All of the Following Standards:}
n _{LTPoE++ 38.7W, 52.7W, 70W and 90W}
n _{IEEE 802.3at 25.5W Compliant}
n _{IEEE 802.3af Up to 13W Compliant}
n _{LT4275B is IEEE 802.3at/af Compliant}
n _{LT4275C is IEEE 802.3af Compliant}
n _{100V Absolute Maximum Input Voltage}
n _{Wide Junction Temperature Range (–40°C to 125°C)}
n _{Overtemperature Protection}
n _{Integrated Signature Resistor}
n _{External Hot Swap™ N-Channel MOSFET for Lowest}
Power Dissipation and Highest System Efficiency
n _{Programmable Aux Power Support as Low as 9V}
n _{Optional Support of Non-Standard Low Voltage PoE}
n _{Available in 10-Lead MSOP and 3mm × 3mm DFN}
Packages
Applications
n _{High Power Wireless Data Systems}
n _{Outdoor Security Camera Equipment}
n _{Commercial and Public Information Displays}
n _{High Temperature Industrial Applications}
LT4275
LTPoE++/PoE+/PoE
PD Controller
Description
The LT^®4275 is a pin-for-pin compatible family of IEEE
802.3 and LTPoE++ powered device (PD) controllers.
The LT4275A employs a proprietary LTPoE++ classification
scheme, delivering 38.7W, 52.7W, 70W or 90W of power
at the PD RJ45 connector. The LT4275A is fully compat-
ible with IEEE 802.3. The LT4275B is an IEEE 802.3at
compliant, Type 2 (PoE+) PD delivering up to 25.5W. The
LT4275C is an IEEE 802.3af compliant, Type 1 (PoE) PD
delivering up to 13W.
The LT4275 internal charge pump provides an N-channel
MOSFET solution, eliminating a larger and more costly
P-channel MOSFET. A low R_DS(ON) MOSFET also maxi-
mizes power delivery and efficiency, reduces power and
heat dissipation, and eases thermal design. Startup inrush
current is adjustable with an external capacitor. The LT4275
also includes a power good output, on-board signature
resistor, undervoltage lockout, and thermal protection. The
LT4275A/LT4275B drives a single opto-coupler to indicate
the power level of the attached PSE. Pin-selectable sup-
port for non-standard low voltage operation is provided.
Auxiliary power override is supported with the AUX pin.
The LT4275A can be configured to support all possible
LTPoE++, 802.3at and 802.3af power levels with external
component changes.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
LTPoE++ and Hot Swap are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Typical Application
LTPoE++ 90W Powered Device Interface
V_AUX (9V TO 60V)
~
DATA
PAIR
~
~
SPARE
PAIR _~
+
V_PORT
–
+
–
C_PD
0.1µF
FDMC86102
+
C_PORT
3.3k
47nF
VPORT HSGATE
AUX
HSSRC
PWRGD
V_IN
ISOLATED
POWER
SUPPLY
RUN
+
V_OUT
–
R_CLS
RCLASS
RCLASS++
LT4275A
R_CLS++ ^{GND IEEEUVLO}
T2P
4275 TA01a
OPTO
PSE TYPE
(TO µP)
LT4275 Family
MAX DELIVERED
POWER
LTPoE++ 90W
LTPoE++ 70W
LTPoE++ 52.7W
LTPoE++ 38.7W
25.5W
13W
LT4275 GRADE
A
B
C
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