19-2708; Rev 0; 4/03
+48V, Single-Port Network Power Switch
For Power-Over-LAN
General Description
The MAX5922A/B/C is a single-port network power con-
troller with an integrated power MOSFET, operating from
a +32V to +60V supply rail. The device is specifically
designed for power-sourcing equipment (PSE) in power-
over-LAN applications and is fully compliant to the IEEE
802.3af standard. The MAX5922 provides power devices
(PD) discovery, classification, current limit, and other nec-
essary functions for an IEEE 802.3af compliant PSE.
The MAX5922 is suitable for PSE function in both
switch/router systems where the power is delivered to the
load through the signal pairs, and in midspan systems
where the power is delivered to the load through the
spare pairs. In midspan mode, a detection collision
avoidance circuit (MAX5922A/C only) provides the nec-
essary back-off timing to prevent fault detections that
happen when two different PSEs try to detect and
power the same PD. The MAX5922B/C have a detec-
tion disable input that can be connected high to disable
the detection/classification functions or connected low
to enable them.
The MAX5922 features a programmable undervoltage
lockout (UVLO) that keeps the device in shutdown until
the input voltage exceeds a certain threshold, set to 38V
(MAX5922A) or 28V (MAX5922B/C) internally. After suc-
cessfully discovering and classifying a PD, the MAX5922
enters startup mode. During startup, the MAX5922 limits
the output voltage and current slew rate to minimize EMI
(electromagnetic interference). The MAX5922 has an inte-
grated 0.45Ω N-channel power MOSFET that provides
efficient operation and simplified system design. The
MAX5922 monitors and provides current-limit protection
to the load at all times. The current limit is programmable
using an external current-sensing resistor. The MAX5922
features current-limit foldback and duty-cycle limit to
ensure robust operation during load-fault and short-circuit
conditions. Fault management allows the part to either
latch-off or autorestart after a fault.
The MAX5922 provides POK,
ZC,
and
FAULT
status sig-
nals to indicate output power is good, zero-current fault,
and other faults (overcurrent, overtemperature), respec-
tively. The MAX5922 is available in a 28-pin TSSOP pack-
age and is rated over the extended -40°C to +85°C
temperature range.
o
IEEE 802.3af Compliant
o
+32V to +60V Wide Operating Input Range
o
0.45Ω Integrated Power Switch
o
Power Device (PD) Detection and Classification
o
100µA PD Leakage Detection Tolerant
o
Programmable Current Limit
o
Zero-Current Detection with Status Output
o
Detection Collision Avoidance Option for Midspan
Application
o
Input Logic Signals Compatible with 1.8V to 5V
CMOS Logic
o
Separate Analog and Digital Grounds with Up to
±4V Offset
o
Power-Good Status Output
o
Overcurrent and Overtemperature Protection with
Status Outputs
o
Current-Limit Foldback with Timeout and Duty-
Cycle Control
o
Latch or Autorestart Fault Management
Features
MAX5922
Ordering Information
PART
MAX5922AEUI
MAX5922BEUI
MAX5922CEUI
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 TSSOP
28 TSSOP
28 TSSOP
Applications
Power-Sourcing Equipment (PSE)
Power-Over-LAN/Power-Over-MDI
(Media-Dependent Interface)
Computer Telephony
Single-Port Power Injector/Adapter
Midspan Power Injector
Switches/Routers with In-Line Power
Typical Application Circuits, Selector Guide, and Pin
Configuration appear at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
+48V, Single-Port Network Power Switch
For Power-Over-LAN
MAX5922
ABSOLUTE MAXIMUM RATINGS
(All voltages with respect to AGND_S, unless otherwise noted.)
IN ............................................................................-0.3V to +76V
UVLO ........................................................................-0.3V to +6V
V
DIG
to DGND ..........................................................-0.3V to +6V
OUT .......................................................-0.3V to (V
DRAIN
+ 0.3V)
DRAIN ..........................................................-0.3V to (V
IN
+ 0.3V)
RDT.........................................................................-0.3V to +12V
RCL to IN ................................................................-10V to +0.3V
EN, DET_DIS, DCA, CLASS, ZC_EN,
and LATCH to DGND ...........................................-0.3V to +6V
POK,
ZC,
CL0, CL1, CL2, and
FAULT
to DGND......-0.3V to +6V
DGND ..........................................................................-5V to +5V
Maximum Current into Drain .................................................0.8A
Maximum Current into POK,
ZC,
CL0, CL1, CL2,
FAULT...20mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin TSSOP (Derate 12.8mW/°C above +70°C) .....1026mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
IN
= 48V, V
DIG
= 3.3V, AGND_S = AGND = DGND = 0V, R
SENSE
= 0.5Ω ±1%, UVLO = open, EN = V
DIG
, R
RCL
= 150Ω ±1%, R
RDT
= 18.2kΩ ±1%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Analog Input Voltage Range
Analog Input Supply Current
Digital Input Voltage Range
Digital Input Supply Current
DGND to AGND Operating
Voltage Range
Current-Limit Response Time
OUT Current-Limit Foldback
Voltage
Current-Limit Sense Voltage
(V
IN
- V
DRS
) (Note 4)
Current-Limit Sense Foldback
Voltage (V
IN
- V
DRS
)
Overcurrent Timeout
D
MOS
On-Resistance
Power-Off OUT Sink Current
Maximum Output Voltage Slew
Rate
Maximum Output Current Slew
Rate
Power-OK Threshold (V
IN
- V
OUT
)
POK Output Low Voltage
POK Output Leakage Current
dV
OUT
/dt
dI
OUT
/dt
V
THPOK
V
FBSTOP
OUT shorted to AGND (Note 2)
(Note 3)
Maximum voltage across R
SENSE
at V
OUT
>
V
FBSTOP
0°C to +70°C
V
ILIM_fb
t
OC
R
DSON
V
OUT
= 0V
OUT shorted to AGND (Note 5)
I
OUT
= 100mA
T
A
= +25°C
T
A
= +85°C
198
203
64
50
SYMBOL
V
IN
I
IN
V
DIG
I
DIG
V
DIG
= 5V
-4
1
18
212
212
70
60
0.45
0.75
15
100
35
650
750
10
0.4
0.05
1
850
223
221
76
75
mV
ms
Ω
µA
V/ms
A/ms
mV
%
V
µA
V
IN
= 60V, measured at AGND after OUT
has stopped slewing
1.65
0.05
CONDITIONS
MIN
32
1
TYP
MAX
60
1.6
5.50
0.1
+4
UNITS
V
mA
V
mA
V
µs
V
V
ILIM
mV
EN = DGND, V
OUT
= 48V
V
OUT
rising, no load
V
OUT
rising, C
LOAD
= 100µF
V
OUT
rising, POK from low to high
Hysteresis
V
POK_LOW
I
POK
= 3mA
V
POK
= 3.3V
2
_______________________________________________________________________________________
+48V, Single-Port Network Power Switch
For Power-Over-LAN
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 48V, V
DIG
= 3.3V, AGND_S = AGND = DGND = 0V, R
SENSE
= 0.5Ω ±1%, UVLO = open, EN = V
DIG
, R
RCL
= 150Ω ±1%, R
RDT
= 18.2kΩ ±1%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
POK Output Delay (Note 6)
Zero-Current Detection Threshold
Voltage (V
IN
- V
DRS
)
ZC
Output Low Voltage
ZC
Output Leakage Current
Zero-Current Detection Delay
Zero-Current Deglitch Time
Thermal Shutdown
Shutdown Autorestart Time
UNDERVOLTAGE LOCKOUT
MAX5922A
UVLO floating, V
IN
rising
Default V
IN
UVLO
UVLO
TH
Hysteresis
Referenced to AGND_S,
V
UVLO
rising
UVLO Comparator Threshold
V
REF
Hysteresis
UVLO Input Resistance
LOGIC SIGNALS
EN, LATCH, DCA, DET_DIS
CLASS, and ZC_EN Input High
Voltage
EN, LATCH, DCA, DET_DIS
CLASS, and ZC_EN Input Low
Voltage
EN, LATCH, DCA, DET_DIS
CLASS, and ZC_EN Input Current
EN Low Pulse Width
FAULT,
CL0, CL1 and CL2,
Output Low Voltage
FAULT,
CL0, CL1 and CL2,
Output Leakage Current
V
OL
I
SINK
= 3mA
V
FAULT
= V
CL0
= V
CL1
= V
CL2
= 3.3V,
CLASS = 0V
0.05
V
IH
1.65V < V
DIG
< 5.5V
0.7
×
V
DIG
0.3
×
V
DIG
0.8
-1
3
0.4
1
+1
µA
µs
V
µA
V
MAX5922B/
MAX5922C
MAX5922A
MAX5922B/C
MAX5922A
MAX5922B/
MAX5922C
MAX5922A
MAX5922B/
MAX5922C
50
1.36
1.31
36
26
38
28
4.4
2.5
1.38
1.33
160
120
mV
kΩ
1.41
1.36
V
40
30
V
t
RESTART
t
ZCDEL
t
ZC_DEG
SYMBOL
t
POK_LOW
CONDITIONS
POK from high to low, V
OUT
falling
MIN
1.0
74
2.7
TYP
1.4
88
3.75
MAX
1.8
102
4.8
0.4
0.05
300
350
10
150
30
1.60
1.92
2.24
1
400
UNITS
ms
mV
V
µA
ms
ms
°C
°C
s
MAX5922
t
POK_HIGH
POK from low to high, V
OUT
rising
V
ZCTH
V
ZC_LOW
(Note 4)
I
ZC
= 3mA
V
ZC
= 3.3V
ZC
from high to low, I
OUT
falling (Note 7)
I
OUT
rising
Temperature rising
Hysteresis
LATCH = low (Note 8)
V
IL
1.65V < V
DIG
< 2.0V
2.0V < V
DIG
< 5.5V
V
_______________________________________________________________________________________
3
+48V, Single-Port Network Power Switch
For Power-Over-LAN
MAX5922
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 48V, V
DIG
= 3.3V, AGND_S = AGND = DGND = 0V, R
SENSE
= 0.5Ω ±1%, UVLO = open, EN = V
DIG
, R
RCL
= 150Ω ±1%, R
RDT
= 18.2kΩ ±1%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Detection Probe Voltage Phase I
Detection Probe Voltage Phase II
Detection Short-Circuit Current
Valid PD Detected Lower-Limit
Threshold
Valid PD Detected Upper-Limit
Threshold
Total Detection Time
Reject Capacitance During
Detection
Allowable Capacitance During
Detection
SYMBOL
V
PBI
V
PBII
I
SC_DET
R
PDL
R
PDH
t
det
C
PDH
C
PDL
R
PD
= 19kΩ to 26.5kΩ
R
PD
= 19kΩ to 26.5kΩ
6
0.6
CONDITIONS
R
PD
= 19kΩ to 26.5kΩ
R
PD
= 19kΩ to 26.5kΩ
OUT shorted to AGND
(Note 9)
(Note 9)
MIN
3.6
7.2
0.68
15
26.5
170
TYP
4
8
MAX
4.4
8.8
1.50
19
33.0
196
UNITS
V
V
mA
kΩ
kΩ
ms
µF
µF
PD DETECTION (See Figure 3,
PD Detection
Section)
PD CLASSIFICATION (See
PD Classification Mode
Section)
Classification Probe Voltage
Classification Short-Circuit
Current
Classification Time Duration
Total Detection and Classification
Delay Time
Class 0 to Class 1 Threshold
Class 1 to Class 2 Threshold
Class 2 to Class 3 Threshold
Class 3 to Class 4 Threshold
Default To Class 0 High-Current
Lower-Limit Threshold
Collision Detection Delay Time
(MAX5922A/MAX5922C Only)
V
CLASS
I
OUT
= 0.5mA to 45mA
No load
48
15
21.3
191
5.5
13
21
31
43
DCA = high, R
PD
= 15kΩ
2.38
6.5
14.5
23
33
46.5
2.8
3.22
15
20
28
65
26
230
7.5
16
25
35
V
mA
ms
ms
mA
mA
mA
mA
mA
s
I
SC_CLASS
Shorted to AGND
t
CLASS
t
TOT
I
CLASS_1L
I
CLASS_1-2
I
CLASS_2-3
I
CLASS_3-4
I
CLASS_4-0
t
DCA
From detection completion
From channel-enabled to power delivered
at the OUT pin
Note 1:
All specifications are 100% production tested at T
A
= +25°C, unless otherwise noted. All temperature limits are guaranteed by
design.
Note 2:
This is the time from an output overcurrent or short-circuit condition until the output goes into regulated current limit.
Note 3:
OUT voltage above which the output current limit is at its full value (see Figure 8).
Note 4:
To be consistent with the IEEE 802.3af standard, choose R
SENSE
= 0.5Ω ±1%.
Note 5:
This is the time the part stays in current-limit mode during overload condition. After t
OC
elapses (or when the junction temperature
hits +150°C) the part shuts down.
Note 6:
See the
Typical Operating Characteristics
and Figure 6.
Note 7:
This is the delay from I
OUT
falling below the zero-current threshold until
ZC
goes low and the IC shuts down (see the
Zero-Current
Detection
section).
Note 8:
See the
Fault Management
section.
Note 9:
PD is detected by the procedures specified by the IEEE 802.3af standard. A probe voltage V
PBI
(+4V typically) is forced at OUT
and the current I
S1
is measured after t
DET
/2. A second probe voltage V
PBII
(+8V typically) is then forced and I
S2
measured after
t
DET
/ 2 again. The voltage increment is then divided by the difference of the two currents (I
S2
- I
S1
). This is the PD resistance value.
4
_______________________________________________________________________________________
+48V, Single-Port Network Power Switch
For Power-Over-LAN
Typical Operating Characteristics
(MAX5922A, V
IN
= 48V, V
DIG
, EN, LATCH, CLASS, and ZC_EN = 3.3V, DCA, AGND_S = AGND = DGND = 0V, R
SENSE
= 0.5Ω ±1%,
UVLO floating, R
RCL
= 150kΩ, R
RDT
= 18.2kΩ, T
A
= +25°C, unless otherwise noted.)
V
IN
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX5922 toc01
MAX5922
V
IN
SUPPLY CURRENT
vs. TEMPERATURE
MEASURED AT
AGND
MAX5922 toc02
DIGITAL SUPPLY CURRENT
vs. TEMPERATURE
11.9
11.8
11.7
MAX5922 toc03
1.00
MEASURED AT AGND
0.95
SUPPLY CURRENT (mA)
0.90
0.85
0.80
T
A
= -40°C
0.75
0.70
32
37
42
47
52
57
T
A
= +25°C
T
A
= +85°C
1.00
0.95
SUPPLY CURRENT (mA)
0.90
0.85
0.80
0.75
0.70
V
IN
= 48V
V
IN
= 60V
12.0
I
DIG
(µA)
11.6
11.5
11.4
V
IN
= 32V
11.3
11.2
11.1
11.0
62
-40 -25 -10
5
20
35
50
65
80
-40
-25
-10
5
20
35
50
65
80
INPUT VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
V
IN
UNDERVOLTAGE LOCKOUT
vs. TEMPERATURE
MAX5922 toc04
MOSFET R
DSON
vs. TEMPERATURE
0.60
0.55
ON-RESISTANCE (Ω)
0.50
0.45
0.40
0.35
0.30
I
OUT
= 100mA
MAX5922 toc05
SENSE TRIP VOLTAGE
vs. TEMPERATURE
214
SENSE TRIP VOLTAGE (V)
213
212
211
210
209
208
207
206
205
V
IN
= 32V
V
IN
= 60V
V
IN
= 48V
MAX5922 toc06
40.0
39.0
DEFAULT V
IN
UVLO (V)
38.0
37.0
36.0
35.0
34.0
33.0
32.0
-40 -25 -10
5
20
35
50
65
80
TEMPERATURE (°C)
V
IN
FALLING
V
IN
RISING
215
-40 -25 -10
5
20
35
50
65
80
-40 -25 -10
5
20
35
50
65
80
TEMPERATURE (°C)
TEMPERATURE (°C)
FOLDBACK-CURRENT LIMIT
(ILIM vs. V
OUT
)
ZERO-CURRENT THRESHOLD VOLTAGE (mV)
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
0
5
10 15 20 25 30 35 40 45 50
OUTPUT VOLTAGE (V)
ILIM (A)
MAX5922 toc07
ZERO-CURRENT DETECTION THRESHOLD
VOLTAGE vs. TEMPERATURE
MAX5922 toc08
ON-RESISTANCE vs. V
DRAIN
I
OUT
= 100mA
0.7
ON-RESISTANCE (Ω)
0.6
T
A
= +25°C
0.5
0.4
0.3
0.2
0.1
T
A
= -40°C
T
A
= +85°C
MAX5922 toc09
3.70
3.68
3.66
3.64
3.62
3.60
3.58
3.56
3.54
3.52
3.50
-40 -25 -10
5
20
35
50
65
80
TEMPERATURE (°C)
V
IN
= 32V
V
IN
= 48V
V
IN
= 60V
0.8
28
32
36
40
44
48
52
56
60
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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