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19-3069; Rev 4; 6/06
KIT
ATION
EVALU
BLE
AVAILA
IEEE 802.3af-Compliant Power-Over-Ethernet
Interface/PWM Controller for Power Devices
General Description
The MAX5941A/MAX5941B integrate a complete power
IC for powered devices (PD) in a power-over-ethernet
(PoE) system. The MAX5941A/MAX5941B provide a PD
interface and a compact DC-DC PWM controller suitable
for flyback and forward converters in either isolated or
nonisolated designs.
The MAX5941A/MAX5941B PD interface complies with
the IEEE 802.3af standard, providing the PD with a detec-
tion signature, a classification signature, and an integrat-
ed isolation switch with programmable inrush current
control. These devices also feature power-mode under-
voltage lockout (UVLO) with wide hysteresis and power-
good status outputs.
The MAX5941A/MAX5941B also integrate all the building
blocks necessary for implementing DC-DC fixed-
frequency isolated power supplies. These devices are a
current-mode controller with an integrated high startup
circuit suitable for isolated telecom/industrial voltage-
range power supplies. A high-voltage startup circuit
allows the PWM controller to draw power directly from the
18V to 67V input supply during startup. The switching fre-
quency is internally trimmed to 275kHz ±10%, thus
reducing magnetics and filter components. The
MAX5941A allows an 85% operating duty cycle and can
be used to implement flyback converters. The MAX5941B
limits the operating duty cycle to less than 50% and can
be used in single-ended forward converters. The
MAX5941A/MAX5941B are designed to work with or with-
out an external diode bridge in front of the PD.
The MAX5941A/MAX5941B are available in 16-pin SO
packages.
Features
o
Powered Device Interface
Fully Integrated IEEE 802.3af-Compliant PD
Interface
PD Detection and Programmable Classification
Signatures
Less than 10µA Leakage Current Offset During
Detection
Integrated MOSFET for Isolation and Inrush
Current Limiting
Gate Output Allows External Control of the
Internal Isolation FET
Programmable Inrush Current Control
Programmable Undervoltage Lockout
o
PWM Controller
Wide Input Range: 18V to 67V
Current-Mode Control
Leading-Edge Blanking
Internally Trimmed 275kHz ±10% Oscillator
Soft-Start
MAX5941A/MAX5941B
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
MAX DUTY
CYCLE (%)
85
85
50
50
MAX5941AESE
-40°C to +85°C 16 SO (S16M-6)
MAX5941ACSE
MAX5941BCSE
0°C to +70°C 16 SO (S16M-6)
0°C to +70°C 16 SO (S16M-6)
MAX5941BESE
-40°C to +85°C 16 SO (S16M-6)
Applications
IP Phones
Wireless Access Nodes
Internet Appliances
Computer Telephony
Security Cameras
Power Devices in Power-Over-Ethernet/
Power-Over-MDI
Pin Configuration
TOP VIEW
V+ 1
V
DD
2
OPTO 3
SS_SHDN 4
ULVO 5
16 V
CC
15 NDRV
14 V-
MAX5941A
MAX5941B
13 CS
12 GND
11 PGOOD
10 PGOOD
9
OUT
Typical Operating Circuit appears at end of data sheet.
RCL 6
GATE 7
V
EE
8
SO
________________________________________________________________
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.
IEEE 802.3af-Compliant Power-Over-Ethernet
Interface/PWM Controller for Power Devices
MAX5941A/MAX5941B
ABSOLUTE MAXIMUM RATINGS
(All voltages are referenced to V
EE
, unless otherwise noted.)
GND........................................................................-0.3V to +90V
OUT,
PGOOD
...........................................-0.3V to (GND + 0.3V)
RCL, GATE .............................................................-0.3V to +12V
UVLO ........................................................................-0.3V to +8V
PGOOD to OUT.........................................-0.3V to (GND + 0.3V)
V+ to V-...................................................................-0.3V to +90V
V
DD
to V-.................................................................-0.3V to +40V
V
CC
to V-..............................................................-0.3V to +12.5V
OPTO, NDRV, SS_SHDN, CS to V-.............-0.3V to (V
CC
+ 0.3V)
Maximum Input/Output Current (Continuous)
OUT to V
EE
...................................................................500mA
GND, RCL to V
EE
............................................................70mA
UVLO,
PGOOD,
PGOOD to V
EE
.....................................20mA
GATE to V
EE
....................................................................80mA
V
DD
, V
CC
.........................................................................20mA
NDRV Continuous ...........................................................25mA
NDRV (Pulsed for less than 1µs) .......................................±1A
Continuous Power Dissipation (T
A
= +70°C)
16-Pin SO (derate 9.1mW/°C above +70°C)................727mW
Operating Temperature Range
MAX5941_CSE ..................................................0°C to +70°C
MAX5941_ESE ...............................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°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
= (GND - V
EE
) = 48V, GATE =
PGOOD
= PGOOD = OPEN, V- tied to OUT, V+ tied to GND, UVLO = V
EE
, T
A
= T
MIN
to +T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C. All voltages are referenced to V
EE
, unless otherwise noted.) (Note 1)
PARAMETER
PD INTERFACE
DETECTION MODE
Input Offset Current
Effective Differential Input
Resistance
CLASSIFICATION MODE
Classification Current Turn-Off
Threshold
V
TH,CLSS
V
IN
rising (Note 4)
Class 0, R
CL
= 10kΩ
Classification Current (Notes 5, 6)
I
CLASS
Class 1, R
CL
= 732Ω
V
IN
= 12.6V
to 20V, R
DISC
Class 2, R
CL
= 392Ω
= 25.5kΩ
Class 3, R
CL
= 255Ω
Class 4, R
CL
= 178Ω
POWER MODE
Operating Supply Voltage
Operating Supply Current
Default Power Turn-On Voltage
Default Power Turn-Off Voltage
Default Power Turn-On/Off
Hysteresis
External UVLO Programming
Range
UVLO External Reference Voltage
V
IN
I
IN
V
UVLO, ON
V
IN
= (GND - V
EE
)
Measure at GND, not including R
DISC
V
IN
increasing, UVLO = V
EE
37.4
30
7.4
Set UVLO externally (Note 7)
12
2.400
2.460
67
2.522
0.4
38.6
67
1
40.1
V
mA
V
V
V
V
V
20.8
0
9.17
17.29
26.45
36.6
21.8
22.5
2
11.83
19.71
29.55
41.4
mA
V
I
OFFSET
dR
V
IN
= 1.4V to 10.1V, GND = V- = OUT = V+
(Note 2)
V
IN
= 1.4V up to 10.1V with 1V step, OUT =
PGOOD
= GND = OUT = V+ (Note 3)
550
10
µA
kΩ
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
UVLO, OFF
V
IN
decreasing, UVLO = V
EE
V
HYST,
UVLO
V
IN,EX
V
REF, UVLO
V
UVLO
increasing
2
_______________________________________________________________________________________
IEEE 802.3af-Compliant Power-Over-Ethernet
Interface/PWM Controller for Power Devices
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= (GND - V
EE
) = 48V, GATE =
PGOOD
= PGOOD = OPEN, V- tied to OUT, V+ tied to GND, UVLO = V
EE
, T
A
= T
MIN
to +T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C. All voltages are referenced to V
EE
, unless otherwise noted.) (Note 1)
PARAMETER
UVLO External Reference Voltage
Hysteresis
UVLO Bias Current
UVLO Input Ground Sense
Threshold
UVLO Input Ground Sense Glitch
Rejection
Power Turn-Off Voltage,
Undervoltage Lockout Deglitch
Time
t
OFF_DLY
SYMBOL
HYST
I
UVLO
CONDITIONS
Ratio to V
REF,UVLO
UVLO = 2.460V
MIN
19.2
-1.5
50
7
TYP
20
MAX
20.9
+1.5
440
UNITS
%
µA
mV
µs
MAX5941A/MAX5941B
V
TH,G,UVLO
(Note 8)
UVLO = V
EE
V
IN
, V
UVLO
falling (Note 9)
T
A
= +25°C
(Note 11)
T
A
= +85°C
0.32
ms
Isolation Switch N-Channel
MOSFET On-Resistance
R
ON
Output current =
300mA, V
GATE
= 5.6V,
measured between
OUT and V
EE
0.6
0.8
0.5
38
5
5.58
1.15
10
5.76
1.23
70
4.62
4.76
80
1.1
Ω
1.5
V
80
15
5.93
1.31
Ω
µA
V
V
mV
4.91
0.4
0.2
1
1
V
mV
V
V
µA
µA
Isolation Switch N-Channel
MOSFET Off-Threshold Voltage
GATE Pulldown Switch Resistance
GATE Charging Current
GATE High Voltage
PGOOD,
PGOOD
Assertion V
OUT
Threshold
PGOOD,
PGOOD
Assertion V
GATE
Threshold
PGOOD
Output Low Voltage
PGOOD Output Low Voltage
PGOOD Leakage Current
PGOOD
Leakage Current
V
GSTH
R
G
I
G
V
GATE
V
OUTEN
OUT = GND, V
GATE
- V
EE,
output current
< 1µA
Power-off mode, V
IN
= 12V, UVLO = V
EE
V
GATE
= 2V
I
GATE
= 1µA
V
OUT
- V
EE
, |V
OUT
- V
EE
| decreasing,
V
GATE
= 5.75V
Hysteresis
(GATE - V
EE
) increasing, OUT = V
EE
Hysteresis
I
SINK
= 2mA (Note 10)
I
SINK
= 2mA, OUT
≤
(GND - 5V) (Note 10)
GATE = high, GND - V
OUT
= 67V (Note 10)
GATE = V
EE
,
PGOOD
- V
EE
= 67V (Note 10)
V
GSEN
V
OLDCDC
ELECTRICAL CHARACTERISTICS (PWM Controller)
(All voltages referenced to V-. V
DD
= 13V, a 10µF capacitor connects V
CC
to V-, V
CS
= V-, V+ = 48V, 0.1µF capacitor connected to
SS_SHDN, NDRV = open circuit, OPTO = V-, T
A
= T
MIN
to +T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SUPPLY CURRENT
I
V+(NS)
V+ Supply Current
V+ Supply Current After Startup
V
DD
Supply Current
I
VDD(NS)
I
VDD(S)
I
V+(S)
V
DD
= 0V, V+ = 67V, driver not switching
V+ = 67V, V
DD
= 0V, V
OPTO
= 4V, driver
switching
V+ = 67V, V
DD
= 13V, V
OPTO
= 4V
V
DD
= 36V, driver not switching
V
DD
= 36V, driver switching, V
OPTO
= 4V
0.85
1.4
11
0.9
1.9
1.3
2.7
1.3
2.6
mA
µA
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
_______________________________________________________________________________________
3
IEEE 802.3af-Compliant Power-Over-Ethernet
Interface/PWM Controller for Power Devices
MAX5941A/MAX5941B
ELECTRICAL CHARACTERISTICS (PWM Controller) (continued)
(All voltages referenced to V-. V
DD
= 13V, a 10µF capacitor connects V
CC
to V-, V
CS
= V-, V+ = 48V, 0.1µF capacitor connected to
SS_SHDN, NDRV = open circuit, OPTO = V-, T
A
= T
MIN
to +T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
V+ Shutdown Current
V
DD
Shutdown Current
PREREGULATORS/STARTUP
V+ Input Voltage
V
DD
Supply Voltage
INTERNAL REGULATORS
V
CC
Output Voltage
V
CC
Undervoltage Lockout
OUTPUT DRIVER
Peak Source Current
Peak Sink Current
NDRV High-Side Driver
Resistance
NDRV Low-Side Driver
Resistance
PWM COMPARATOR
OPTO Input Bias Current
OPTO Control Range
Slope Compensation
THERMAL SHUTDOWN
Thermal Shutdown Temperature
Thermal Hysteresis
CURRENT LIMIT
CS Threshold Voltage
CS Input Bias Current
Current-Limit Comparator
Propagation Delay
CS Blanking Time
OSCILLATOR
Clock Frequency Range
Max Duty Cycle
SOFT-START
SS Source Current
SS Sink Current
Peak Soft-Start Voltage Clamp
Shutdown Threshold
No external load
V
SS_SHDN
falling (Note 11)
V
SS_SHDN
rising (Note 11)
I
SSO
V
SS(SHDN)
= 0V
2.0
1
2.331
0.25
0.53
2.420
0.37
0.59
2.500
0.41
0.65
4.6
6.5
µA
mA
V
V
V
OPTO
= 4V
MAX5941A, V
OPTO
= 4V
MAX5941B, V
OPTO
= 4V
235
75
44
275
314
85
50
kHz
%
V
ILIM
V
OPTO
= 4V
0V
≤
V
CS
≤
2V, V
OPTO
= 4V
25mV overdrive on CS, V
OPTO
= 4V
V
OPTO
= 4V
419
-1
180
70
465
510
+1
mV
µA
ns
ns
150
25
°C
°C
V
SCOMP
MAX5941A
V
OPTO
= V
SS_SHDN
-1.00
2
26
+1.00
3
µA
V
mV/µs
R
OH
R
OL
V
CC
= 11V (externally forced)
V
CC
= 11V (externally forced)
V
CC
= 11V, externally forced, NDRV
sourcing 50mA
V
CC
= 11V, externally forced, NDRV sinking
50mA
570
1000
4
1.6
12
4
mA
mA
Ω
Ω
V
CC_UVLO
Powered from V+, I
CC
= 7.5mA, V
DD
= 0V
Powered from V
DD
, I
CC
= 7.5mA
V
CC
falling
7.5
9.0
9.8
10.0
6.6
12
11.0
V
V
18
13
67
36
V
V
SYMBOL
CONDITIONS
V
SS_SHDN
= 0V, V+ = 67V
V
SS_SHDN
= 0V
MIN
TYP
190
8
MAX
290
20
UNITS
µA
µA
4
_______________________________________________________________________________________
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