Linear 1351A Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1351A
DESCRIPTION
Demonstration circuit 1351A is a high-power supply
featuring the LTC ® 4269IDKD-2. This board acts as
an IEEE 802.3at compliant, high power Power-over-
Ethernet (PoE), Powered Device (PD) and connects
at the RJ45 to a compatible high power Power
Sourcing Equipment (PSE) device, such as the
DC1366A.
The LTC4269IDKD-2 provides IEEE802.3at standard
(PoE+) PD interfacing and power supply control.
When the PD is fully powered, the PD interface
switches power over from the PSE to the switcher
through an internal, low resistance, high power
MOSFET. The highly integrated LTC4269IDKD-2 con-
Table 1. Performance Summary (T
PARAMETER
Port Voltage (V )
PORT
Auxiliary Voltage (V )
AUX
Output Voltage (V ) Initial Set-point
OUT
Maximum Output Current
Typical Output Voltage Ripple
Output Regulation
Load Transient Response
Switching Frequency
Efficiency

OPERATING PRINCIPLES

A compatible high power PSE board, such as the
DC1366A, is connected to the DC1351A at the RJ45
connector J2 (see the schematic). As required by
IEEE802.3at, a diode bridge is used across the data
pairs and signal pairs. Schottky diodes (D5-8, D12-
15) are used at the input to improve efficiency over
SINGLE OUTPUT, HIGH POWER, HIGH EFFICIENCY POE
= 25°C)
A
CONDITION
At Ethernet port
From Aux- to Aux+ terminals
V = 37V to 57V, I
PORT
V = 42V
PORT
V = 50V, I = 4.6A
IN OUT
Over Entire Input Voltage and Output Current Range
Peak to Peak Deviation with Load Step of 2.5A to 5A
Settling Time (within 1% of V
V PORT = 42V, I OUT = 5A, not incl. diode bridge
trols a high-power, small-sized power supply that
utilizes a highly-efficient isolated forward topology
with synchronous rectification. The DC1351A sup-
plies a 5V output at up to 5A.
DC1351A also demonstrates the use of an auxiliary
48V wall adapter. When present, the auxiliary supply
becomes the dominant supply over PoE to provide
power.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
= 0A to 5A
OUT
)
OUT
standard diode bridges. The LTC4269IDKD-2 pro-
vides an IEEE802.3at standard PoE 25k signature re-
sistance and is set for a power class 4. When the PD
is powered and voltage is above the PoE ''On Volt-
age'', the LTC4269IDKD-2 switches the port voltage
over to the power supply controller through its inter-
LTC4269IDKD-2
VALUE
37V – 57V
44V – 57V
5.05V ± 1%
4.6A (min)
40mV (typ)
P–P
< ±0.1% (typ)
±120mV (< ±2.5%) (typ)
150us (typ)
225kHz (typ)
92.5% (typ)
1