LTC4267-3 Datasheet, PDF (1/32 Pages) Linear Technology – Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator

LTC4267-3
Power over Ethernet
IEEE 802.3af PD Interface with
Integrated Switching Regulator
FEATURES
n _{Complete Power Interface Port for IEEE 802}^®_.3af
Powered Device (PD)
n _{Onboard 100V, UVLO Switch}
n _{Constant-Frequency 300kHz Operation}
n _{Precision Dual Level Inrush Current Limit}
n _{Integrated Current Mode Switching Regulator}
n _{Onboard 25k Signature Resistor with Disable}
n _{Programmable Classification Current (Class 0-4)}
n _{Thermal Overload Protection}
n _{Power Good Signal}
n _{Integrated Error Amplifier and Voltage Reference}
n _{Low Profile 16-Pin SSOP or DFN Packages}
U
APPLICATIO S
n _{IP Phone Power Management}
n _{Wireless Access Points}
n _{Security Cameras}
n _{Power over Ethernet}
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTIO
The LTC^®4267-3 combines an IEEE 802.3af compliant
Powered Device (PD) interface with a 300kHz current mode
switching regulator, providing a complete power solution
for PD applications. The LTC4267-3 integrates the 25k
signature resistor, classification current source, thermal
overload protection, signature disable and power good
signal along with an undervoltage lockout optimized for
use with the IEEE-required diode bridge. The LTC4267-3
provides an increased operational current limit, maximizing
power available for class 3 applications.
The 300kHz current mode switching regulator provides
higher output power or smaller external size compared
to its lower frequency counterparts. The LTC4267-3 is
designed for driving a 6V rated N-channel MOSFET and
features programmable slope compensation, soft-start,
and constant-frequency operation, minimizing noise even
with light loads. The LTC4267-3 includes an onboard er-
ror amplifier and voltage reference allowing use in both
isolated and nonisolated configurations.
The LTC4267-3 is available in a space saving, low profile
16-pin SSOP or DFN packages.
TYPICAL APPLICATIO
Class 2 PD with 3.3V Isolated Power Supply
PA1133 SBM1040
–48V
FROM
DATA PAIR
+
HD01
–
–48V
FROM
SPARE PAIR
+
HD01
–
V_PORTP
P_VCC
SMAJ58A
PWRGD
LTC4267-3
NGATE
0.1µF
SENSE
R_CLASS
68.1Ω
1%
R_CLASS I_TH/RUN
V_FB
SIGDISA PGND
V_PORTN
P_OUT
10k
+
P_VCC ⁺
4.7µF
•
5µF
MIN
320µF
• ^MIN
10k ^Si3440
P_VCC
0.1Ω
6.8k
BAS516
PS2911
470Ω
22nF
TLV431
3.3V
1.5A
CHASSIS
100k
60.4k
42671 TA01
42673f
1