LTC4263CS#TRPBF Linear Technology, LTC4263CS#TRPBF Datasheet - Page 13

• Manufacturer Part Number: LTC4263CS#TRPBF
• Description: IC IEEE 803.2AF CNTRLR 14-SOIC
• Manufacturer: Linear Technology
• Type: Power Over Ethernet (PoE)r

Specifications of LTC4263CS#TRPBF

• Applications: Power Interface Switch for Power Over Ethernet (PoE) Devices
• Voltage - Supply: 48V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Current - Supply: 1mA
• Interface: IEEE 802.3af
• Controller Type: Power Sourcing Equipment Controller (PSE)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
Table 2. LTC4263 Power Management
When additional current is added to the PWRMGT node,
the voltage rises toward the 1V threshold. After adding
current, the LTC4263 verifi es that the power supply is not
over-allocated by verifying the node voltage remains below
1V. If the voltage is below 1V, the LTC4263 proceeds to
power the port. If over 1V, the current is removed from
the node, port powering is aborted, and the LTC4263 goes
back into detection mode.
Power Management
The LTC4263 includes a power management feature
allowing simple implementation of power management
across multiple ports driven by a single power supply. The
PWRMGT pins of all LTC4263 devices are tied together
along with an RC network to prevent over-allocation of
power in a multi-port system.
Immediately following classifi cation, the LTC4263 performs
a power management check to ensure power is available
to supply the newly classed PD. The allocated power is
represented by the voltage on the shared PWRMGT node
and the LTC4263 checks the allocated power by measur-
ing this voltage. If the PWRMGT voltage is less than 1V,
there is power available and the power needs of the new
PD are added to the already allocated power on the node.
To allocate power, a current proportional to the power
needs for the new PD is sourced out of the PWRMGT pin
(Table 2).
IEEE 802.3af
CLASS
0, 3, 4
2
1
POWER REQUIRED
PSE OUTPUT
15.4W
7W
4W
LTC4263 PWRMGT
CURRENT
–72.3μA
–32.8μA
–18.8μA
For multiple LTC4263s implementing power management,
the PWRMGT pins are connected together and to a RC
network connected to V
R
power supply (P
full load output power using the following formula:
The LTC4263 power management uses pulse width
modulation to set the power requirements of each PD.
Capacitor C
average power requirement for all PDs in the system. Set
C
If power management is not used, tie PWRMGT to V
PM
PM
R
represents the full load output capability of the system
PM
to 1μF.
=
P
213 Ω •
V
PM
FULL LOAD
SS
Figure 5. PWRMGT Pin Connections
is used as a lowpass fi lter to generate the
k
FULL_LOAD
_
R
PM
W
SS
as shown in Figure 5. The value of
). Select a 1% resistor to set the
C
1μF
PM
PWRMGT
V
PWRMGT
V
PWRMGT
V
PWRMGT
V
SS
SS
SS
SS
LTC4263
LTC4263
LTC4263
LTC4263
LTC4263
4263 F05
13
4263fe
SS
.