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LTC4257CS8-1#PBF 数据手册 - Linear Technology（凌力尔特）
制造商:
Linear Technology（凌力尔特）
分类:
主动器件
封装:
SOIC-8
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LTC4257CS8-1#PBF数据手册
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LTC4257-1
1
42571fb
The LTC
®
4257-1 provides complete signature and power
interface functions for a device operating in an IEEE
802.3af Power over Ethernet (PoE) system. The LTC4257-1
simplifies Powered Device (PD) design by incorporating
the 25k signature resistor, classification current source,
input current limit, undervoltage lockout, thermal over-
load protection, signature disable and power good signal-
ling, all in a single 8-pin package. The LTC4257-1 includes
a precision, dual level current limit circuit. This allows it to
charge large load capacitors and interface with legacy
Power over Ethernet systems while maintaining compat-
ibility with the current IEEE 802.3af specification. By
incorporating a high voltage power MOSFET onboard, the
LTC4257-1 provides the system designer with reduced
cost while also saving board space.
The LTC4257-1 can interface directly with a variety of Lin-
ear Technology DC/DC converter products to provide a cost
effective power solution for IP phones, wireless access
points and other PDs. Linear Technology also provides
network power controllers for Power Sourcing Equipment
(PSE) applications.
The LTC4257-1 is available in the 8-pin SO and low profile
(3mm × 3mm) DFN packages.
■
IP Phone Power Management
■
Wireless Access Points
■
Telecom Power Control
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
Complete Power Interface Port for IEEE 802
®
.3af
Powered Devices (PDs)
■
Onboard 100V, 400mA Power MOSFET
■
Precision Dual Level Current Limit
■
Onboard 25k Signature Resistor with Disable
■
Programmable Classification Current (Class 0-4)
■
Undervoltage Lockout
■
Thermal Overload Protection
■
Power Good Signal
■
Available in 8-Pin SO and Low Profile (3mm × 3mm)
DFN Packages
IEEE 802.3af PD
Power over Ethernet Interface
Controller with Dual Current Limit
GND
R
CLASS
R
CLASS
SMAJ58A
0.1µF
SIGDISA
PWRGD
LTC4257-1
V
IN
SHDN
100k
5µF
MIN
3.3V
TO LOGIC
RTN
SWITCHING
POWER SUPPLY
V
IN
V
OUT
–48V FROM
POWER SOURCING
EQUIPMENT
(PSE)
42571 TA01
+
–
+
DF01SA
~
~
+
–
Powered Device (PD)
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
All other trademarks are the property of their respective owners.
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