LINEAR TECHNOLOGY LTC4267 User's Guide
Summary
This detailed manual describes the LTC4267, a highly integrated IC designed for complete power management solutions in IEEE 802.3af Power over Ethernet (PoE) applications. It combines an advanced PD interface with an onboard switching regulator, offering crucial features like programmable classification current, dual-level inrush current limiting, and thermal protection. Ideal for engineers developing low-power networking equipment—such as IP phones, Wi-Fi access points, and security cameras—this component ensures reliable and efficient power delivery to various powered devices.
Page 1 Text Content
LTC4267
Power over Ethernet
IEEE 802.3af PD Interface with Integrated Switching Regulator
FEATURES DESCRIPTIO ■ Complete Power Interface Port for IEEE 802®.3af
The LTC®4267 combines an IEEE 802.3af compliant Pow-
Powered Device (PD) ered Device (PD) interface with a current mode switching ■ Onboard 100V, 400m A UVLO Switch
regulator, providing a complete power solution for PD
■ Precision Dual Level Inrush Current Limit
applications. The LTC4267 integrates the 25kΩ signature
■ Integrated Current Mode Switching Regulator
resistor, classifi cation current source, thermal overload pro-
■ Onboard 25kΩ Signature Resistor with Disable
tection, signature disable and power good signal along with
■ Programmable Classifi cation Current (Class 0-4)
an undervoltage lockout optimized for use with the IEEE-
■ Thermal Overload Protection
required diode bridge. The precision dual level input current
■ Power Good Signal
limit allows the LTC4267 to charge large load capacitors
■ Integrated Error Amplifi er and Voltage Reference
and interface with legacy Po E systems.
■ Low Profi le 16-Pin SSOP and 3mm × 5mm DFN
The current mode switching regulator is designed for
Packages
driving a 6V rated N-channel MOSFET and features pro- grammable slope compensation, soft-start, and constant
APPLICATIO frequency operation, minimizing noise even with light
loads. The LTC4267 includes an onboard error amplifi er
■ IP Phone Power Management
and voltage reference allowing use in both isolated and
■ Wireless Access Points
nonisolated confi gurations.
■ Security Cameras
■ Power over Ethernet
The LTC4267 is available in space saving, low profi le 16-pin SSOP or DFN packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
Class 2 PD with 3.3V Isolated Power Supply
PA1133 SBM1040
FROM HD01 VPORTP PVCC
PVCC 320µF
DATA PAIR 5µF CHASSIS
PWRGD 4.7µF
LTC4267
SMAJ58A
NGATE
Si3440 10k
0.1µF SENSE
PVCC 0.1Ω
RCLASS ITH/RUN
–48V RCLASS
HD01 68.1Ω 6.8k
FROM VFB
SPARE PAIR 1%
SIGDISA PGND 22n F
BAS516
VPORTN POUT
PS2911
TLV431 60.4k
4267 TA01
4267fb
Page Summary Contents For LINEAR TECHNOLOGY LTC4267 User's Guide
Manual Details
| Brand | Linear |
|---|---|
| Pages | 32 |
| File Size | 2.00 MB |
| Published | June 17, 2026 |
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Frequently Asked Questions
What power standards does the LTC4267 comply with?
It is compliant with IEEE 802.3af for Power over Ethernet (PoE) and includes adjustable Class I/Run settings.
What protection features are integrated into the device?
The unit incorporates UVLO, programmable classification current limits, thermal overload protection, and a dual level input current limit.
Can this chip be used for various applications beyond typical PoE devices?
Yes, it is optimized for IP Phone Power Management, Wireless Access Points (WAPs), and Security Cameras in both isolated and non-isolated configurations.
What are the available operating temperature ranges for different packages?
The LTC4267C operates from 0°C to 70°C, while the outdoor version, LTC4267I, handles -40°C to 85°C.