LTC4259A Datasheet, PDF (1/32 Pages) Linear Technology – Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect

LTC4259A
Quad IEEE 802.3af
Power over Ethernet Controller
with AC Disconnect
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 AC or 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}
s _{Available in a 36-Pin SSOP Package}
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^®4259A is a quad –48V Hot Swap^TM controller
designed 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 LTC4259A can implement a complete IEEE
802.3af-compliant PSE.
The LTC4259A can operate autonomously or be controlled
by an I²C serial interface. Up to 16 LTC4259As may coexist
on the same data bus, allowing up to 64 powered Ethernet
ports to be controlled with only two digital lines. Fault con-
ditions 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 LTC4259A 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
–48V
SCL INT
SDAIN
SDAOUT
AD0
AD1
AD2
AD3
SHDN1 SHDN2 SHDN3 SHDN4
V_DD
LTC4259A
OSCIN AUTO BYP
RESET
DETECT1
DETECT2
DETECT3
DETECT4
DGND AGND V_EE SENSE1 GATE1 OUT1 SENSE2 GATE2 OUT2 SENSE3 GATE3 OUT3 SENSE4 GATE4 OUT4
R_S1
10k
10k
10k
10k
CMPD3003
×4
1k
×4
0.47µF
100V ×4
X7R
0.1µF
Q1
R_S2
Q2
R_S3
Q3
R_S4
RS1 TO RS4: 0.5Ω
Q1 TO Q4: IRFM120A
Q4
S1B ×4
Figure 1. Complete 4-Port Powered Ethernet Power Source
0.1µF 100V SMAJ58A
×4
×4
PORT1
PORT2
PORT3
PORT4
4259A F01
4259Af
1