Linear Technology LTC4267 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 859
DESCRIPTION
Demonstration circuit 859 is a Multiple Output PD fea-
turing the LTC4267. The board provides a complete
IEEE 802.3af power device (PD) interface and isolated
power supply solution for use in Power over Ethernet
(PoE) applications. It generates 1.8V @ 2.5A, 2.5V @
1.5A and 3.3V @ 0.5A.
The LTC4267 integrates the 25kΩ signature resistor,
classification current source, thermal overload protec-
tion, signature disable and power good signal along with
an undervoltage lockout optimized for use with the IEEE
required diode bridge. The precision dual level input
current limit allows the LTC4267 to charge load capaci-
tors and interface with legacy PoE systems.
Table 1. Performance Summary (T
PARAMETER
Turn-on Voltage
Maximum Turn-off Voltage
Power Converter Input operating range
Maximum Input Current
Maximum Output Current
Output Voltage
Output Regulation
= 25°C)
A
CONDITION
Input from PSE
Input from PSE, PD switch turns off
V =3.3V, I = 0 to 2.6A
OUT OUT
Input from PSE, PD high level current limit
V =1.8V
OUT1
V =2.5V
OUT2
V =3.3V
OUT3
V =48VDC from PSE
IN
V = 1.8V, V = -37 to -57VDC, zero to full load
OUT1 IN
V = 2.5V, V = -37 to -57VDC, zero to full load
OUT2 IN
V = 3.3V, V = -37 to -57VDC, zero to full load
OUT3 IN
The LTC4267 combines the above features with a cur-
rent mode switching controller designed for driving a 6V
rated N-channel MOSFET.
slope compensation, soft-start, and constant frequency
operation, minimizing electrical noise even with light
loads.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
MULTIPLE OUTPUT PD
LTC4267
It features programmable
VALUE
-36V maximum
-32V
-37V to -57V
375 mA, typical
2.5A
1.5A
0.5A
1.79V, typical
2.5V, typical
3.3V, typical
+ 5%
+ 2%
+ 5%
1