LTC4269-2 Datasheet, PDF (1/34 Pages) Linear Technology – IEEE 802.3at High Power PD and Synchronous Forward Controller with AUX Support

Features
n _{25.5W IEEE 802.3at Compliant (Type-2) PD}
n _PoE⁺ _{2-Event Classification}
n _{IEEE 802.3at High Power Available Indicator}
n _{Integrated State-of-the-Art Synchronous Forward}
Controller
– Isolated Power Supply Efficiency >94%
n _{Flexible Auxiliary Power Interface}
n _{Superior EMI Performance}
n _{Robust 100V 0.7Ω (Typ) Integrated Hot Swap™}
MOSFET
n _{Integrated Signature Resistor, Programmable Class}
Current, UVLO, OVLO and Thermal Protection
n _{Short-Circuit Protection with Auto-Restart}
n _{Programmable Switching Frequency from}
100kHz to 500kHz
n _{Thermally Enhanced 7mm × 4mm DFN Package}
Applications
n _{IP Phones with Large Color Screens}
n _{Dual Radio 802.11n Access Points}
n _{PTZ Security Cameras}
LTC4269-2
IEEE 802.3at High Power PD
and Synchronous Forward
Controller with AUX Support
Description
The LTC^®4269-2 is an integrated Powered Device (PD)
interface and power supply controller featuring 2-event
classification signaling, flexible auxiliary power op-
tions, and a power supply controller suitable for syn-
chronously rectified forward supplies. These features
make the LTC4269-2 ideally suited for an IEEE802.3at
PD application.
The PD controller features a 100V MOSFET that isolates
the power supply during detection and classification, and
provides 100mA inrush current limit. Also included are
power good outputs, an undervoltage/overvoltage lock-
out and thermal protection. The current mode forward
controller allows for synchronous rectification, resulting
in an extremely high efficiency, green product. Soft-start
for controlled output voltage start-up and fault recovery is
included. Programmable frequency over 100kHz to 500kHz
allows flexibility in efficiency vs size and low EMI.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Hot Swap, ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Typical Application
PoE-Based Self-Driven Synchronous Forward Power Supply
1mH
•
10µH
+
10µF
54V FROM
DATA PAIR
~+
~–
2.2µF _237k
10.0k
33k
4.7nF
V_CC
0.1µF
+
10µF
10k
133Ω
•
5.1Ω
•
6.8µH
5V
+
5A
220µF
54V FROM
SPARE PAIR
~+
~–
0.1µF
30.9Ω
SD_V_SEC PWRGD V_IN
V_PORTP
S_OUT
OUT
OC
I_SENSE
R_CLASS
SHDN
LTC4269-2
COMP
FB
V_PORTN
V_REF
T2P V_NEG PGND GND BLANK DELAY R_OSC SS_MAXDC
1.5k
33k 22k
22.1k
TO
MICRO-
CONTROLLER
82k 332k 158k 158k
0.22µF
V_CC
50mΩ
1.2k
0.1µF
TLV431
4.7nF
2k
11.3k
10nF
3.65k
42692 TA01
42692fb