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MAX5942BCSE+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
General Description
The MAX5942A/MAX5942B integrate a complete power
IC for powered devices (PD) in a power-over-ethernet
(PoE) system. The MAX5942A/MAX5942B provide a PD
interface and a compact DC-DC PWM controller suitable
for flyback and forward converters in either isolated or
nonisolated designs.
The MAX5942A/MAX5942B PD interface complies with
the IEEE™ 802.3af standard, providing the PD with a
detection signature, a classification signature, and an
integrated isolation switch with programmable inrush cur-
rent control. These devices also feature power-mode
undervoltage lockout (UVLO) with wide hysteresis and
power-good status outputs.
The MAX5942A/MAX5942B also integrate all the build-
ing blocks necessary for implementing DC-DC fixed-
frequency isolated power supplies. This device is 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
frequency is internally trimmed to 275kHz ±10%, thus
reducing magnetics and filter components. The
MAX5942A allows an 85% operating duty cycle and can
be used to implement flyback converters. The MAX5942B
limits the operating duty cycle to less than 50% and can
be used in single-ended forward converters. The
MAX5942A/MAX5942B are designed to work with or with-
out an external diode bridge in front of the PD.
The MAX5942A/MAX5942B are available in 16-pin SO
packages.
Applications
IP Phones
Wireless Access Nodes
Internet Appliances
Computer Telephony
Security Cameras
Power Devices in Power-Over-Ethernet/
Power-Over-MDI
Features
♦ 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/ULVO
PGOOD/PGOOD Outputs Enable PWM
Controller
♦ PWM Controller
Wide Input Range: 18V to 67V
Isolated (Without Optocoupler) or Nonisolated
Power Supply
Current-Mode Control
Leading-Edge Blanking
Internally Trimmed 275kHz ±10% Oscillator
Soft-Start
MAX5942A/MAX5942B
IEEE 802.3af Power-Over-Ethernet
Interface/PWM Controller for Power Devices
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3024; Rev 2; 9/04
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
PART
TEMP RANGE
PIN-
PACKAGE
M A X D U T Y
C YC L E ( % )
MAX5942AESE*
-40°C to +85°C
16 SO 85
MAX5942ACSE
0°C to +70°C
16 SO 85
MAX5942BESE*
-40°C to +85°C
16 SO 50
MAX5942BCSE
0°C to +70°C
16 SO 50
Typical Operating Circuit appears at end of data sheet.
IEEE is a trademark of the Institute of Electrical and Electronics
Engineers.
*Future product—contact factory for availability.
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
V+
V
CC
NDRV
V-
CS
GND
PGOOD
PGOOD
OUT
TOP VIEW
MAX5942A
MAX5942B
SO
V
DD
FB
RCL
SS_SHDN
ULVO
GATE
V
EE
Pin Configuration
MAX5942A/MAX5942B
IEEE 802.3af Power-Over-Ethernet
Interface/PWM Controller for Power Devices
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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)
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.
(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 +80V
V
DD
to V-.................................................................-0.3V to +40V
V
CC
to V-..............................................................-0.3V to +12.5V
FB, 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 Ranges
MAX5942_CSE...................................................0°C to +70°C
MAX5942_ESE................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) ................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
PD INTERFACE
DETECTION MODE
Input Offset Current
I
OFFSET
V
IN
= 1.4V to 10.1V (Note 2) 10 µA
Effective Differential Input
Resistance
dR
V
IN
= 1.4V up to 10.1V with 1V step,
OUT = PGOOD = GND (Note 3)
550
kΩ
CLASSIFICATION MODE
Classification Current Turn-Off
Threshold
V
TH
CLSS
V
IN
rising (Note 4)
20.8 21.8 22.5
V
Class 0, R
CL
= 10kΩ 02
Class 1, R
CL
= 732Ω
9.17 11.83
Class 2, R
CL
= 392Ω
17.29 19.71
Class 3, R
CL
= 255Ω
26.45 29.55
Classification Current I
CLASS
V
IN
= 12.6V
to 20V, R
DISC
= 25.5kΩ
(Notes 5, 6)
Class 4, R
CL
= 178Ω
36.6 41.4
mA
POWER MODE
Operating Supply Voltage V
IN
V
IN
= (GND - V
EE
)67V
Operating Supply Current I
IN
Measure at GND, not including R
DISC
0.4
1mA
Default Power Turn-On Voltage
V
UVLO
ON
V
IN
increasing, UVLO = V
EE
37.4 38.6 40.1
V
Default Power Turn-Off Voltage
V
UVLO
OFF
V
IN
decreasing, UVLO = V
EE
30 V
Default Power Turn-On/Off
Hysteresis
V
HYST
UVLO
7.4 V
External UVLO Programming
Range
V
IN,EX
Set UVLO externally (Note 7) 12 67 V
UVLO External Reference Voltage
V
REF
UVLO
V
UVLO
increasing
2.400 2.460 2.522
V
UVLO External Reference
Voltage Hysteresis
HYST Ratio to V
REF,UVLO
19.2
20
20.9
%
MAX5942A/MAX5942B
IEEE 802.3af Power-Over-Ethernet
Interface/PWM Controller for Power Devices
_______________________________________________________________________________________ 3
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
UVLO Bias Current I
UVLO
UVLO = 2.460V
-1.5 +1.5
µA
UVLO Input Ground Sense
Threshold
V
TH
G
UVLO
(Note 8) 50 440 mV
UVLO Input Ground Sense Glitch
Rejection
UVLO = V
EE
7µs
Power Turn-Off Voltage,
Undervoltage Lockout Deglitch
Time
t
OFF_DLY
V
IN
, V
UVLO
falling (Note 9)
0.32
ms
T
A
= +25°C
(Note 11)
0.6
1.1
Isolation Switch N-Channel
MOSFET On-Resistance
R
ON
Output current =
300mA, V
GATE
= 5.6V,
measured between
OUT and V
EE
T
A
= +85°C
0.8
1.5
Ω
Isolation Switch N-Channel
MOSFET Off-Threshold Voltage
V
GSTH
OUT = GND, V
GATE
- V
EE,
output current
< 1µA
0.5 V
GATE Pulldown Switch Resistance
R
G
Power-off mode, V
IN
= 12V, UVLO = V
EE
38 80 Ω
GATE Charging Current I
G
V
GATE
= 2V 5 10 15 µA
GATE High Voltage V
GATE
I
GATE
= 1µA
5.58 5.76 5.93
V
V
OUT
- V
EE
, |V
OUT
- V
EE
| decreasing,
V
GATE
= 5.75V
1.15 1.23 1.31
V
PGOOD, PGOOD Assertion
V
OUT
Threshold
V
OUTEN
Hysteresis 70 mV
(GATE - V
EE
) increasing, OUT = V
EE
4.62 4.76 4.91
V
PGOOD, PGOOD Assertion
V
GATE
Threshold
V
GSEN
Hysteresis 80 mV
PGOOD Output Low Voltage
V
OLDCDC
I
SINK
= 2mA (Note 10) 0.4 V
PGOOD Output Low Voltage I
SINK
= 2mA, OUT ≤ (GND - 5V) (Note 10) 0.2 V
PGOOD Leakag e C ur r ent GATE = hi g h, GN D - V
OU T
= 67V ( N ote 10) 1 µA
PGOOD Leakag e C ur r ent GATE = V
E E
, P GOOD - V
E E
= 67V ( N ote 10) 1 µA
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)
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, V
FB
= 3V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SUPPLY CURRENT
I
V+(NS)
V
DD
= 0V, V+ = 67V, driver not switching 0.8 1.6
V+ Supply Current
I
V+(S)
V+ = 67V, V
DD
= 0V, V
FB
= 4V, driver
switching
1.6 3.2
mA
V+ Supply Current After Startup V+ = 67V, V
DD
= 13V, V
FB
= 4V 14 µA
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24

MAX5942BCSE+T

Mfr. #:
Buy MAX5942BCSE+T
Manufacturer:
Maxim Integrated
Description:
I/O Controller Interface IC IEEE 802.3af POE Int/PWM Controller
Lifecycle:
New from this manufacturer.
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