LTC4258 Datasheet, PDF (1/28 Pages) Linear Technology – Quad IEEE 802.3af Power over Ethernet Controller with Integrated Detection

Electrical Specifications Subject to Change
LTC4258
Quad IEEE 802.3af
Power over Ethernet Controller
with Integrated Detection
FEATURES
DESCRIPTIO
s _{Controls Four Independent – 48V Powered}
Ethernet Ports
s _{Each Port Includes:}
– IEEE 802^®.3af Compliant PD Detection and
Classification
– Output Current Limit with Foldback
– Short-Circuit Protection with Fast Gate Pull-Down
– PD Disconnect Using DC Sensing
– Power Good Indication
s _{Operates Autonomously or Controlled by I}²_C^TM
Serial Interface
s _{4-Bit Programmable Digital Address Allows Control}
of Up to 64 Ports
s _{Programmable INT Pin Eliminates Software Polling}
s _{Current and Duty Cycle Limits Protect External FETs}
U
APPLICATIO S
s _{IEEE 802.3af Compliant Endpoint and Midspan}
Power Sources
s _{IP Phone Systems}
s _{DTE Power Distribution}
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation. 802 is a registered trademark of
Instutute of Electrical and Electronics Engineers, Inc. I²C is a trademark of Philips Electronics N.V.
The LTC^®4258 is a quad –48V Hot Swap^TM controller de-
signed for use in IEEE 802.3af compliant Power
Sourcing Equipment (PSE). It consists of four independent
ports, each with output current limit, short-circuit protec-
tion, complete Powered Device (PD) detection and classi-
fication capability, and programmable PD disconnect using
AC or DC sensing. Used with power MOSFETs and passives
as in Figure 1, the LTC4258 can implement a complete IEEE
802.3af-compliant PSE.
The LTC4258 can operate autonomously or be controlled by
an I²C serial interface. Up to 16 LTC4258s may coexist on
the same data bus, allowing up to 64 powered Ethernet ports
to be controlled with only two digital lines. Fault conditions
are optionally signaled with the INT pin to eliminate software
polling.
External power MOSFETs, current sense resistors and di-
odes allow easy scaling of current and power dissipation
levels and provide protection against voltage and current
spikes and ESD events.
The LTC4258 is available in a 36-pin SSOP package.
Linear Technology also provides solutions for 802.3af PD
applications with the LTC4257 and LTC4257-1.
TYPICAL APPLICATIO
3.3V
0.1µF
0.1µF
100V X7R
SCL INT
SDAIN
SDAOUT
AD0
AD1
AD2
AD3
SHDN1 SHDN2 SHDN3 SHDN4
V_DD
LTC4258
AUTO BYP
RESET
DETECT1
DETECT2
DETECT3
DETECT4
DGND AGND V_EE SENSE1 GATE1 OUT1 SENSE2 GATE2 OUT2 SENSE3 GATE3 OUT3 SENSE4 GATE4 OUT4
CMPD3003
×4
R_S1
10k
10k
10k
10k
–48V
0.1µF
Q1
R_S2
Q2
R_S3
Q3
R_S4
RS1 TO RS4: 0.5Ω
Q4
Q1 TO Q4: IRFM120A
Figure 1. Complete 4-Port Powered Ethernet Power Source
0.1µF 100V SMAJ58A
×4
×4
OUT1
OUT2
OUT3
OUT4
4258 F01
4258p
1