EVALUATION KIT AVAILABLE
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Benefits and Features
General Description
The MAX5988A/MAX5988B provide a complete power-
supply solution as IEEE
®
802.3af-compliant Class 1/
Class 2 Powered Devices (PDs) in a Power-over-Ethernet
(PoE) system. The devices integrate the PD interface with
an efficient DC-DC converter, offering a low external part
count PD solution. The devices also include a low-drop-
out regulator, MPS, sleep, and ultra-low-power modes.
The PD interface provides a detection signature and
a Class 1/Class 2 classification signature with a single
external resistor. The PD interface also provides an isola-
tion power MOSFET, a 60mA (max) inrush current limit,
and a 321mA (typ) operating current limit.
The integrated step-down DC-DC converter uses a peak
current-mode control scheme and provides an easy-to-
implement architecture with a fast transient response.
The step-down converter operates in a wide input volt-
age range from 8.8V to 60V and supports up to 6.49W of
input power at 1.3A load. The DC-DC converter operates
at a fixed 215kHz switching frequency, with an efficiency-
boosting frequency foldback that reduces the switching
frequency by half at light loads.
The devices feature an input undervoltage-lockout
(UVLO) with wide hysteresis and long deglitch time to
compensate for twisted-pair cable resistive drop and to
assure glitch-free transition during power-on/-off condi-
tions. The devices also feature overtemperature shut-
down, short-circuit protection, output overvoltage protec-
tion, and hiccup current limit for enhanced performance
and reliability.
All devices are available in a 20-pin, 4mm x 4mm, TQFN
power package and operate over the -40°C to +85°C
temperature range.
●
High Integration Saves Space and BOM Cost
•
Efficient, Integrated DC-DC Converter (with
Integrated Switches)
• Built-In Output-Voltage Monitoring
•
Protects Against Overload, Output Short Circuit,
Output Overvoltage, and Overtemperature
• Integrated TVS Diode Withstands Cable Discharge
Event (CDE)
• Internal LDO Regulator with Up to 100mA Load
●
Application-Specific Features Speed Design
• IEEE 802.3af Compliant
•
PoE Class 1/Class 2 Classification Set with Single
Resistor
•
Intelligent Maintain Power Signature (MPS)
•
Simplified Wall Adapter Interface
•
Pass 2kV, 200m CAT-6 Cable Discharge Event
●
High Efficiency During Light Loads Reduces Power
Consumption
• Sleep and Ultra-Low-Power Mode
•
Frequency Foldback for High-Efficiency Light-Load
Operation
•
Back-Bias Capability to Optimize the Efficiency
●
Robust Performance
•
8.8V to 60V Wide Input Voltage Range
• Hiccup-Mode Runaway Current Limit
•
49mA (typ) Inrush Current Limit
• Open-Drain
RESET
Output
●
Easy to Design With
• 3.0V to 14V Programmable Output Voltage Range
• Internal Compensation
• Fixed 215kHz Switching Frequency
• Fixed 3.3V or Adjustable Output Voltage through
an External Resistive Divider (LDO)
Ordering Information/Selector Guide
appears at end of data
sheet.
Applications
●
●
●
●
●
IEEE 802.3af-Powered Devices
IP Phones
Wireless Access Nodes
IP Security Cameras
WiMAX
®
Base Stations
IEEE is a registered service mark of the Institute of Electrical
and Electronics Engineers, Inc.
WiMAX is a registered certification mark and registered service
mark of WiMAX Forum.
19-6476; Rev 3; 1/15
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
VDRV to V
DD
............................................ -0.3V to (V
DD
+ 0.3V)
PGND to GND ......................................................-0.3V to +0.3V
LX Total RMS Current ...........................................................1.6A
Continuous Power Dissipation (T
A
= + 70NC)
TQFN (derate 28.6mW/NC above +70NC) ..............2285.7mW
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range............................ -65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
Absolute Maximum Ratings
(All voltages referenced to GND, unless otherwise noted.)
V
DD
to GND..........................-0.3V to +70V (internally clamped)
(100V, 100ms, R
TEST
= 3.3kω) (Note 1)
V
CC
, WAD, RREF to GND ........................ -0.3V to (V
DD
+ 0.3V)
AUX, LDO_IN, LED to GND .................................... -0.3V to 16V
LDO_OUT to GND .............................. -0.3V to (LDO_IN + 0.3V)
LDO_FB to GND ......................................................-0.3V to +6V
LX to GND ................................................ -0.3V to (V
CC
+ 0.3V)
LDO_OUT, VDRV, FB,
RESET, WK, SL, ULP,
MPS, CLASS2
to GND ..............................................................-0.3V to +6V
Note 1:
See
Figure 1,
Test Circuit.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion 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.
Package Thermal Characteristics
(Note 2)
Junction-to-Ambient Thermal Resistance (q
JA
) ..............35°C/W
Junction-to-Case Thermal Resistance (q
JC
) ..................2.7°C/W
Note 2:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to
www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(V
DD
= 48V, R
SIG
= 24.9kω, LED, V
CC
,
SL, ULP, WK, RESET,
LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see
Figure 3),
V
FB
= V
AUX
= 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are refer-
enced to GND, unless otherwise noted. T
A
= T
J
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 3)
PARAMETER
POWER DEVICE (PD) INTERFACE
DETECTION MODE
Input Offset Current
Effective Differential Input
Resistance
CLASSIFICATION MODE
Classification Enable Threshold
Classification Disable Threshold
Classification Stability Time
Classification Current
POWER MODE
VDD Supply Voltage Range
VDD Supply Current
VDD
IDD
60
VDD = 60V
3.3
4.5
V
mA
ICLASS
VDD = 12.6V
to 20V
CLASS2 = GND
CLASS2 = VDRV
9.12
16.1
VTH,CLS,EN
VTH,CLS,DIS
VDD rising
VDD rising
10.2
22
11.42
23
2
10.5
18
11.88
20.9
12.5
23.8
V
V
ms
mA
IOFFSET
dR
VVDD = 1.4V to 10.1V (Note 4)
VVDD = 1.4V to 10.1V with 1V step,
(Note 5)
23.95
8
25.5
µA
kω
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
www.maximintegrated.com
Maxim Integrated
│
2
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Electrical Characteristics (continued)
(V
DD
= 48V, R
SIG
= 24.9kω, LED, V
CC
,
SL, ULP, WK, RESET,
LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see
Figure 3),
V
FB
= V
AUX
= 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are refer-
enced to GND, unless otherwise noted. T
A
= T
J
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 3)
PARAMETER
VDD Turn-On Voltage
VDD Turn-Off Voltage
VDD Turn-On/Off Hysteresis
VDD Deglitch Time
Inrush to Operating Mode Delay
Isolation Power MOSFET On-
Resistance
SYMBOL
VON
VOFF
VHYST_UVLO
tOFF_DLY
tDELAY
RON_ISO
CONDITIONS
VDD rising
VDD falling
(Note 6)
VDD falling from 40V to 20V
(Note 5)
tDELAY = time after (VDD - VCC)
from 1.5V to 0V
IVCC = 100mA
TJ = +25°C
TJ = +85°C
MIN
37.2
30
TYP
38.8
31.5
7.3
150
123
1.2
1.5
MAX
40
UNITS
V
V
V
µs
ms
ω
MAINTAIN POWER SIGNATURE (MPS = VDRV)
PoE MPS Current Rising
Threshold
PoE MPS Current Falling
Threshold
PoE MPS Current Threshold
Hysteresis
PoE MPS Output Average
Current
PoE MPS Peak Output Current
PoE MPS Time High
PoE MPS Time Low
CURRENT LIMIT
Inrush Current Limit
Current Limit During Normal
Operation
LOGIC
WAD Detection Rising Threshold
WAD Detection Falling Threshold
WAD Detection Hysteresis
WAD Input Current
CLASS2, MPS Voltage Rising
Threshold
IWAD
VCLASS2, RISE
VWAD = 24V
VWAD_RISE
VWAD_FALL
5.8
0.6
125
2.9
8.8
V
V
V
µA
V
IINRUSH
ILIM
During initial turn-on period,
VDD - VCC = 4V, measured at VCC
After inrush completed, VCC = VDD
- 1.5V, measured at VCC
39
290
49
321
60
360
mA
mA
IMPS_RISE
IMPS_FALL
IMPS_HYS
IMPS_AVE
IMPS_PEAK
IMPS_HIGH
IMPS_LOW
10
18
14
28.7
24
4.3
4.8
12.6
95
190
40
35
mA
mA
mA
mA
mA
ms
ms
www.maximintegrated.com
Maxim Integrated
│
3
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Electrical Characteristics (continued)
(V
DD
= 48V, R
SIG
= 24.9kω, LED, V
CC
,
SL, ULP, WK, RESET,
LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see
Figure 3),
V
FB
= V
AUX
= 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are refer-
enced to GND, unless otherwise noted. T
A
= T
J
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 3)
PARAMETER
CLASS2, MPS Voltage Falling
Threshold
RESET
Output Voltage Low
RESET,
CLASS2, MPS Leakage
VAUX Input Voltage Range
VAUX Input Current
VDRV Output Voltage
SLEEP MODE
WK
and
ULP
Logic Threshold
SL
Logic Threshold
SL
Current
LED Current Amplitude
LED Current Programmable
Range
LED Current with Grounded
SL
LED Current Frequency
LED Current Duty Cycle
VDD Current Amplitude
Internal Current Duty Cycle
Internal Current Enable Time
Internal Current Disable Time
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
LDO
Input Voltage Range
Output Voltage
Max Output Voltage Setting
LDO FB Regulation Voltage
Inferred from line regulation
LDO_FB = VDRV
With external divider to LDO_FB
1.2
1.227
4.5
3.3
5.5
1.25
14
V
V
V
V
TSD
TSD,HYS
TJ rising
151
16
°C
°C
ILED
VTH
V
WK
falling and V
ULP
rising and
falling
Falling
V
SL
= 0V
R
SL
= 60.4kω, VLED = 6.5V
R
SL
= 30.2kω, VLED = 6.5V
R
SL
= 30.2kω, VLED = 3.5V
SYMBOL
VCLASS2, FALL
VOL_RESET
ILOG_LEAK
VAUX
IAUX
Inferred from VAUX input current
VAUX from 4.75V to 14V
ISINK = 1mA
-10
4.75
0.65
4.2
CONDITIONS
MIN
0.4
0.2
+10
14
3.1
5.5
TYP
MAX
UNITS
V
V
µA
V
mA
V
INTERNAL REGULATOR WITH BACK BIAS
1.6
0.55
62.4
9.2
19.2
10.6
21.2
21.2
10
2.9
0.8
12
23.5
V
V
µA
mA
IRANGE
ILED_MAX
fILED
DILED
IVDD
DIVDD
tMP_ENABLE
tMP_DISABLE
V
SL
= 0V
Sleep and ultra-low-power modes
Sleep and ultra-low-power modes
Sleep mode, VLED = 6.5V
Sleep and ultra-low-power modes
Ultra-low-power mode
Ultra-low-power mode
20
26
250
25
31.4
mA
mA
Hz
%
20.6
10
76
205
12
75
88
237
14.5
98
265
mA
%
ms
ms
www.maximintegrated.com
Maxim Integrated
│
4
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Electrical Characteristics (continued)
(V
DD
= 48V, R
SIG
= 24.9kω, LED, V
CC
,
SL, ULP, WK, RESET,
LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see
Figure 3),
V
FB
= V
AUX
= 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are refer-
enced to GND, unless otherwise noted. T
A
= T
J
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 3)
PARAMETER
LDO FB Leakage Current
Dropout
Load Regulation
Line Regulation
Overcurrent Protection
Threshold
LDO_FB Rising Threshold
LDO_FB Hysteresis
DC-DC CONVERTER INPUT SUPPLY
VDD Voltage Range
WAD Detection Rising Threshold
WAD Detection Falling Threshold
WAD Detection Hysteresis
POWER MOSFETs
High-Side pMOS On-Resistance
Low-Side nMOS On-Resistance
LX Leakage Current
SOFT-START (SS)
Soft-Start Time
FEEDBACK (FB)
FB Regulation Voltage
FB Input Bias Current
OUTPUT VOLTAGE
Output Voltage Range
Cycle-by-Cycle Overvoltage
Protection
VOUT
VOUT-OV
MAX5988A
MAX5988B
Rising (Note 8)
Falling (Note 8)
3.0
5.4
100.5
98.5
103
101.1
5.6
14
108
104
V
%
VFB-RG
IFB
VFB = 1.224V
1.203
1.226
10
1.252
200
V
nA
tSS-TH
10
ms
RDSON-H
RDSON-L
ILX-LKG
ILX = 0.5A (sourcing)
ILX = 0.5A (sinking)
VDD = VCC = 28V, VLX = (VPGND
+ 1V) to (VCC - 1V)
-5
0.54
0.14
+5
ω
ω
µA
VDD,RISING
VDD,FALLING
VWAD,RISE
VWAD,FALL
VCC = VDD = VWAD - 0.3V, rising
VCC = VDD = VWAD - 0.3V, falling
(Note 7)
(Note 7)
5.8
0.6
8
7.7
60
60
8.8
V
V
V
V
2.3
IOVC
VDROPOUT
VLDO_IN = 5V, VLDO_FB = VDRV,
ILOAD = 80mA
ILOAD from 1mA to 80mA
VLDO_IN from 4.5V to 14V
85
3.3
2.4
3.7
SYMBOL
CONDITIONS
MIN
-1
300
0.5
1.4
TYP
MAX
+1
UNITS
µA
mV
mV/mA
mV/V
mA
V
V
www.maximintegrated.com
Maxim Integrated
│
5
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