DESCRIPTION
The LTC4257 provides complete signature
and power interface functions for a device
operating in an IEEE 802.3af Power over Ethernet
(PoE) system. The LTC4257 simplifies Powered Device
(PD) design by incorporating the 25k signature resistor,
the classification current source,input current limit with
thermal foldback, undervoltage lockout and power good
signalling, all in a single 8-pin package. By incorporating
a high voltage power MOSFET onboard, the LTC4257 provides
the system designer with reduced cost while also saving board space.
The LTC4257 can interface directly with a variety of Linear
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
solutions for Power Sourcing Equipment (PSE) applica-
tions with quad network power controllers.
The LTC4257 is available in the 8-pin SO and low profile
(3mm×3mm) DFN packages.
FEATURES
Complete Power Interface Port for IEEE 802.3af
Powered Devices (PDs)
Onboard 100V, 400mA Power MOSFET
Precision Input Current Limit
Onboard 25k Signature Resistor
Programmable Classification Current (Class 0-4)
Undervoltage Lockout
Smart Thermal Protection
Power Good Signal
Available in 8-Pin SO and Low Profile (3mm×3mm)
DFN Packages
APPLICATIONS
IP Phone Power Management
Wireless Access Points
Telecom Power
TYPICAL APPLICATION
LTC4257 Charging 300µF Load Capacitor
BLOCK DIAGRA
RELATED PARTS
Burst Mode is a registered trademark of Linear Technology Corporation. No R SENSE
and ThinSOT are trademarks of Linear Technology Corporation
FROM: Company Name: Aunytor Electronic (HK) Co.,Ltd
Contact Person: liao
Skype: Aunytor
Email: 2885745253@qq.com