LTC4258
Quad IEEE 802.3af
Power over Ethernet Controller
with Integrated Detection
FEATURES
■
■
DESCRIPTIO
■
■
■
■
■
Controls Four Independent – 48V Powered
Ethernet Ports
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
Operates Autonomously or by I
2
C
TM
Control
4-Bit Programmable Digital Address Allows Control
of Up to 64 Ports
Programmable INT Pin Eliminates Software Polling
Current and Duty Cycle Limits Protect External FETs
Available in a 36-Pin SSOP Package
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
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 I
2
C 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, LTC4257-1, and LTC4267.
APPLICATIO S
■
■
■
IEEE 802.3af Compliant Endpoint and Midspan
Power Sources
IP Phone Systems
DTE Power Distribution
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Hot Swap is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
INT
SCL
SDAIN
SDAOUT
AD0
AD1
AD2
AD3
3.3V
0.1µF
0.1µF
100V X7R
SHDN1 SHDN2 SHDN3 SHDN4
V
DD
AUTO BYP
RESET
DETECT1
DETECT2
DETECT3
DETECT4
LTC4258
CMPD3003
×4
DGND AGND V
EE
SENSE1 GATE1 OUT1 SENSE2 GATE2 OUT2 SENSE3 GATE3 OUT3 SENSE4 GATE4 OUT4
R
S1
–48V
0.1µF
Q1
10k
R
S2
PORT2
Q2
R
S3
PORT3
Q3
RS1 TO RS4: 0.5Ω
Q1 TO Q4: IRFM120A
R
S4
Q4
PORT4
4258 F01
10k
10k
10k
PORT1
Figure 1. Complete 4-Port Powered Ethernet Power Source
4258fb
U
0.1µF 100V
×4
SMAJ58A
×4
U
U
1
LTC4258
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RESET
BYP
INT
SCL
SDAOUT
SDAIN
AD3
AD2
AD1
Supply Voltages
V
DD
to DGND .......................................... – 0.3V to 5V
V
EE
to AGND ......................................... 0.3V to – 70V
DGND to AGND (Note 2) .................................
±0.3V
Digital Pins
SCL, SDAIN, SDAOUT, INT, AUTO, RESET
SHDNn, ADn
.................
DGND – 0.3V to DGND + 5V
Analog Pins
GATEn (Note 3) ................... V
EE
– 0.3V to V
EE
+ 12V
DETECTn .................... DGND – 21V to DGND + 0.3V
SENSEn
.................................
V
EE
– 0.3V to V
EE
+ 1V
OUTn
....................................
V
EE
– 70V to V
EE
+ 70V
BYP Current .................................................
±0.1mA
Operating Ambient Temperature Range ...... 0°C to 70°C
Junction Temperature (Note 4) ............................ 150°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
1
2
3
4
5
6
7
8
9
36 NC
35 AUTO
34 OUT1
33 GATE1
32 SENSE1
31 OUT2
30 GATE2
29 SENSE2
28 V
EE
27 OUT3
26 GATE3
25 SENSE3
24 OUT4
23 GATE4
22 SENSE4
21 AGND
20 SHDN4
19 SHDN3
ORDER PART
NUMBER
LTC4258CGW
AD0
10
DETECT1
11
DETECT2
12
DETECT3
13
DETECT4
14
DGND
15
V
DD
16
SHDN1
17
SHDN2
18
GW PACKAGE
36-LEAD PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 80°C/W
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. AGND = DGND = 0V, V
DD
= 3.3V, V
EE
= –48V unless otherwise noted
(Note 5).
SYMBOL PARAMETER
Power Supplies
V
DD
V
DD
Supply Voltage
V
EE
V
EE
Supply Voltage
I
DD
V
DD
Supply Current
I
EE
V
EE
Supply Current
V
DDMIN
V
EEMINON
V
EEMINOFF
Detection
I
DET
V
DD
UVLO Voltage
V
EE
UVLO Voltage (Turning On)
V
EE
UVLO Voltage (Turning Off)
Detection Current
CONDITIONS
●
ELECTRICAL CHARACTERISTICS
MIN
3
–47
TYP
3.3
2.5
–2
2.7
–31
–28
MAX
4
–57
5
–5
100
UNITS
V
V
mA
mA
mA
V
V
V
µA
µA
V
kΩ
kΩ
V
mA
4258fb
To Maintain IEEE Compliant Output (Note 6)
Normal Operation
Classification Into a Short (V
DETECTn
= 0V) (Note 8)
V
EE
– AGND
V
EE
– AGND
First Point, V
DETECTn
= –10V
Second Point, V
DETECTn
= –3.5V
Open Circuit, Measured at DETECTn Pin
●
●
●
●
●
●
●
●
●
235
145
15.2
26.7
–16.4
55
–20
17
29
V
DET
Detection Voltage Compliance
R
DETMIN
Minimum Valid Signature Resistance
R
DETMAX
Maximum Valid Signature Resistance
Classification
V
CLASS
Classification Voltage
I
CLASS
Classification Current Compliance
300
190
–23
19
33
–21
75
0mA < I
CLASS
< 31mA
Into Short (V
DETECT
= 0V)
●
●
2
U
W
U
U
W W
W
LTC4258
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. AGND = DGND = 0V, V
DD
= 3.3V, V
EE
= –48V unless otherwise noted
(Note 5).
SYMBOL
I
TCLASS
PARAMETER
Classification Threshold Current
CONDITIONS
Class 0-1
Class 1-2
Class 2-3
Class 3-4
Class 4-Overcurrent
Gate On, V
GATEn
= V
EE
Gate Off, V
GATEn
= V
EE
+ 5V
V
GATEn
= V
EE
+ 2V
I
GATEn
= – 1µA (Note 3)
V
OUTn
– V
EE
0V > V
OUTn
> –10V
–10V > V
OUTn
> –30V
V
OUTn
= –48V
V
SENSEn
– V
EE
, V
OUT
= V
EE
(Note 7)
V
SENSEn
– V
EE
, V
OUTn
= V
EE
V
SENSEn
– V
EE
, V
OUTn
= AGND – 30V
V
SENSEn
– V
EE
, V
OUTn
= AGND – 10V
V
SENSEn
– V
EE
V
SENSEn
= V
EE
I
SDAOUT
= 3mA, I
INT
= 3mA
I
SDAOUT
= 5mA, I
INT
= 5mA
SCL, SDAIN, RESET, SHDNn, AUTO, ADn
SCL, SDAIN, RESET, SHDNn, AUTO, ADn
ADn, RESET, SHDNn
AUTO
From Detect Command or Application of PD to Port
to Detect Complete (Figure 2)
Time to Measure PD Signature Resistance (Figure 2)
From Successful Detect in Auto or Semiauto Mode
to Class Complete
From Classify Command in Manual Mode (Figure 2)
(Figure 2)
From Valid Detect to Port On in Auto Mode (Figure 2)
From Port On Command to GATE Pin Current = I
GON
(Note 9)
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
MIN
5.5
13
21
31
45
–20
30
10
1
TYP
6.5
14.5
23
33
48
–50
50
13
2
MAX
7.5
16
25
35
51
–70
300
15
3
–6
–18
UNITS
mA
mA
mA
mA
mA
µA
µA
mA
V
V
µA
µA
µA
mV
mV
mV
mV
mV
mV
µA
V
V
V
V
kΩ
kΩ
Gate Driver
I
GON
GATE Pin Current
I
GOFF
GATE Pin Current
I
GPD
GATE Pin Short-Circuit Pull-Down
∆V
GATE
External Gate Voltage (V
GATEn
– V
EE
)
Output Voltage Sense
V
PG
Power Good Threshold Voltage
I
VOUT
Out Pin Bias Current
–20
166
201
201
30.2
2.52
187.5
212.5
199
224
224
4.97
Current Sense
V
CUT
Overcurrent Detection Sense Voltage
V
LIM
Current Limit Sense Voltage
V
MIN
DC Disconnect Sense Voltage
V
SC
Short-Circuit Sense Voltage
I
SENSE
SENSE Pin Bias Current
Digital Interface
V
OLD
Digital Output Low Voltage
V
ILD
V
IHD
R
PU
Digital Input Low Voltage
Digital Input High Voltage
Pull-Up Resistor to V
DD
3.75
275
–50
0.4
0.7
0.8
2.4
50
50
170
170
10.1
10.1
10.1
590
230
52
420
13
130
1
R
PD
Pull-Down Resistor to DGND
AC Characteristics
t
DETDLY
Detection Delay
t
DET
t
CLSDLY
Detection Duration
Classification Delay
ms
ms
ms
ms
ms
ms
ms
t
CLASS
t
PON
Classification Duration
Power On Delay, Auto Mode
4258fb
3
LTC4258
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. AGND = DGND = 0V, V
DD
= 3.3V, V
EE
= –48V unless otherwise noted
(Note 5).
SYMBOL
t
START
PARAMETER
Maximum Current Limit Duration During
Port Start-Up
CONDITIONS
t
START1
= 0, t
START0
= 0 (Figure 3)
t
START1
= 0, t
START0
= 1 (Figure 3)
t
START1
= 1, t
START0
= 0 (Figure 3)
t
START1
= 1, t
START0
= 1 (Figure 3)
t
ICUT1
= 0, t
ICUT0
= 0 (Figure 3)
t
ICUT1
= 0, t
ICUT0
= 1 (Figure 3)
t
ICUT1
= 1, t
ICUT0
= 0 (Figure 3)
t
ICUT1
= 1, t
ICUT0
= 1 (Figure 3)
Reg16h = 00h
t
DIS1
= 0, t
DIS0
= 0 (Figure 4)
t
DIS1
= 0, t
DIS0
= 1 (Figure 4)
t
DIS1
= 1, t
DIS0
= 0 (Figure 4)
t
DIS1
= 1, t
DIS0
= 1 (Figure 4)
V
SENSEn
– V
EE
> 5mV, V
OUTn
= –48V (Figure 4)
(Note 9)
(Note 9)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
Figure 5 (Notes 9, 10)
(Notes 9, 10, 11)
(Notes 9, 10, 11)
(Notes 9, 10)
●
●
●
●
●
●
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
t
ICUT
Maximum Current Limit Duration After
Port Start-Up
DC
CLMAX
t
DIS
Maximum Current Limit Duty Cycle
Disconnect Delay
MIN
50
25
100
200
50
25
100
200
5.8
300
75
150
600
t
VMIN
I
2
C Timing
f
SCLK
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
r
t
f
t
FLTINT
t
STOPINT
t
ARAINT
DC Disconnect Minimum Pulse
Width Sensitivity
Clock Frequency
Bus Free Time
Start Hold Time
SCL Low Time
SCL High Time
Data Hold Time
Data Set-Up Time
Start Set-Up Time
Stop Set-Up Time
SCL, SDAIN Rise Time
SCL, SDAIN Fall Time
Fault Present to INT Pin Low
Stop Condition to INT Pin Low
ARA to INT Pin High Time
TYP
60
30
120
240
60
30
120
240
6.3
360
90
180
720
0.02
MAX
70
35
140
280
70
35
140
280
6.7
400
100
200
800
1
UNITS
ms
ms
ms
ms
ms
ms
ms
ms
%
ms
ms
ms
ms
ms
●
●
●
●
●
●
●
●
●
●
●
●
●
●
400
1.3
600
1.3
600
150
200
600
600
20
20
20
60
20
300
150
150
200
300
kHz
µs
ns
µs
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
DGND and AGND should be tied together in normal operation.
Note 3:
An internal clamp limits the GATE pins to a minimum of 12V above
V
EE
. Driving this pin beyond the clamp may damage the part.
Note 4:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 5:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground (AGND and DGND)
unless otherwise specified.
Note 6:
The LTC4258 is designed to maintain a port voltage of –46.6V to
–57V. The V
EE
supply voltage range accounts for the drop across the
MOSFET and sense resistor.
Note 7:
The LTC4258 implements overload current detection per IEEE
802.3af. The minimum overload current (I
CUT
) is dependent on port
voltage; I
CUT_MIN
= 15.4W/V
PORT_MIN
. An IEEE compliant system using the
LTC4258 should maintain port voltage above –46.6V.
Note 8:
V
EE
supply current while classifying a short is measured indirectly
by measuring the DETECTn pin current while classifying a short.
Note 9:
Guaranteed by design, not subject to test.
Note 10:
Values measured at V
ILD
and V
IHD
.
Note 11:
If fault occurs during an I
2
C transaction, the INT pin will not be
pulled down until a stop condition is present on the I
2
C bus.
4258fb
4
LTC4258
TYPICAL PERFOR A CE CHARACTERISTICS
Power On Sequence in Auto Mode
PORT 1
V
DD
= 3.3V
V
EE
= –48V
GND
POWER ON
PORT
VOLTAGE
20V/DIV
V
EE
V
EE
GATE +14V
VOLTAGE
10V/DIV V
EE
PORT
CURRENT 0mA
500mA/DIV
GND
PORT
VOLTAGE
10V/DIV
DETECTION
DETECTION
PHASE 1
PHASE 2
CLASSIFICATION
V
EE
Current Limit Foldback
225
200
175
V
SENSEn
(mV)
PULL-DOWN VOLTAGE (V)
150
125
100
75
50
25
V
DD
= 3.3V
V
EE
= –48V
T
A
= 25°C
–40
–32
–24
–16
–8
0
4258 G03
0
–48
V
OUTn-AGND
(V)
Classification Transient Response
to 40mA Load Step
0
V
DD
= 3.3V
V
EE
= –48V
T
A
= 25°C
–18V
CLASSIFICATION VOLTAGE (V)
–6
–8
–10
–12
–14
–16
–18
–20
PORT VOLTAGE WITH
TYPICAL CMPD3003
DETECTn
PIN VOLTAGE
0
10
20
30
40
50
60
CLASSIFICATION CURRENT (mA)
70
SUPPLY CURRENT (mA)
PORT
VOLTAGE
1V/DIV
40mA
PORT
CURRENT
20mA/DIV
0mA
50µs/DIV
4258 G07
U W
50ms/DIV
Powering On a 180µF Load
V
DD
= 3.3V
V
EE
= –48V
FET ON
LOAD
FULLY
CHARGED
FOLDBACK
425mA
CURRENT LIMIT
5ms/DIV
4258 G01
4258 G02
INT and SDAOUT Pull Down
Voltage vs Load Current
450
400
I
LIMIT
WITH R
SENSE
= 0.5Ω (mA)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
5
15
20
10
LOAD CURRENT (mA)
25
4258 G06
V
DD
= 3.3V
T
A
= 25°C
350
300
250
200
150
100
50
0
Classification Current Compliance
V
DD
= 3.3V
–2 V
EE
= –48V
T = 25°C
–4
A
3.0
2.5
2.0
1.5
1.0
0.5
V
EE
DC Supply Current vs
Supply Voltage
V
DD
= 3.3V
REG 12h = 00h
–50 –40 –30 –20 –10
V
EE
SUPPLY VOLTAGE (V)
0
0
–70 –60
4258 G08
4258 G09
4258fb
5
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