LTC4257CDD#TR Linear Technology, LTC4257CDD#TR Datasheet - Page 5
![IC CONTROLLER POE INTERFACE 8DFN](/photos/7/2/70256/161-8-dfn_sml.jpg)
LTC4257CDD#TR
Manufacturer Part Number
LTC4257CDD#TR
Description
IC CONTROLLER POE INTERFACE 8DFN
Manufacturer
Linear Technology
Type
Power over Ethernet Switch (PoE)r
Datasheet
1.LTC4257CS8PBF.pdf
(20 pages)
Specifications of LTC4257CDD#TR
Applications
IP Phones, Power over LAN, Network Routers and Switches
Internal Switch(s)
Yes
Current Limit
350mA
Operating Temperature
0°C ~ 70°C
Mounting Type
Surface Mount
Package / Case
8-WFDFN Exposed Pad
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
PI FU CTIO S
BLOCK DIAGRA
NC (Pin 1): No Connect.
R
current the LTC4257 maintains during classification. Con-
nect a resistor between R
NC (Pin 3): No Connect.
V
input diode bridge.
V
through an internal power MOSFET that limits input cur-
rent. V
above the turn-on UVLO threshold. Above the UVLO
threshold the output is current limited to 350mA.
IN
OUT
CLASS
U
(Pin 4): Power Input. Tie to system – 48V through the
(Pin 5): Power Output. Supplies – 48V to the PD load
OUT
(Pin 2): External Class Select Input. Used to set the
U
is high impedance until the input voltage rises
R
CLASS
U
V
NC
NC 3
IN
1
2
4
CLASS
W
CONTROL
CIRCUITS
0.3Ω
and V
1.237V
350mA
IN
(see Table 2).
–
+
+
–
CURRENT SOURCE
CLASSIFICATION
EN
EN
CURRENT
INPUT
LIMIT
BOLD LINE INDICATES HIGH CURRENT PATH
PWRGD (Pin 6): Power Good Output, Open-Drain. Signals
that the LTC4257 MOSFET is fully on. Low impedance
indicates power is good. PWRGD is high impedance
during detection, classification and in the event of a
thermal overload. PWRGD is referenced to V
NC (Pin 7): No Connect
GND (Pin 8): Ground. Tie to system ground and to power
return through the input diode bridge.
POWER GOOD
25k SIGNATURE
RESISTOR
8
7
6
5
4257 BD
V
GND
NC
PWRGD
OUT
LTC4257
IN
.
4257fb
5