MAX5988A/MAX5988B IEEE 802.3 af-Compliant
EVALUATION KIT AVAILABLE
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
General Description
The MAX5988A/MAX5988B provide a complete powersupply 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-dropout 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 isolation 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-toimplement architecture with a fast transient response.
The step-down converter operates in a wide input voltage 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 efficiencyboosting 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 conditions. The devices also feature overtemperature shutdown, short-circuit protection, output overvoltage protection, 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.
Applications
●●
●●
●●
●●
●●
IEEE 802.3af-Powered Devices
IP Phones
Wireless Access Nodes
IP Security Cameras
WiMAX® Base Stations
Benefits and Features
●● 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.
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
Absolute Maximum Ratings
(All voltages referenced to GND, unless otherwise noted.)
VDD to GND...........................-0.3V to +70V (internally clamped)
(100V, 100ms, RTEST = 3.3kω) (Note 1)
VCC, WAD, RREF to GND......................... -0.3V to (VDD + 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 (VCC + 0.3V)
LDO_OUT, VDRV, FB, RESET, WK, SL, ULP, MPS, CLASS2
to GND...............................................................-0.3V to +6V
VDRV to VDD............................................. -0.3V to (VDD + 0.3V)
PGND to GND.......................................................-0.3V to +0.3V
LX Total RMS Current............................................................1.6A
Continuous Power Dissipation (TA = + 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
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 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.
Package Thermal Characteristics (Note 2)
Junction-to-Ambient Thermal Resistance (qJA)...............35°C/W
Junction-to-Case Thermal Resistance (qJC)...................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
(VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
8
μA
25.5
kω
POWER DEVICE (PD) INTERFACE
DETECTION MODE
Input Offset Current
Effective Differential Input
Resistance
IOFFSET
dR
VVDD = 1.4V to 10.1V (Note 4)
VVDD = 1.4V to 10.1V with 1V step,
(Note 5)
23.95
CLASSIFICATION MODE
Classification Enable Threshold
Classification Disable Threshold
VTH,CLS,EN
VTH,CLS,DIS
VDD rising
VDD rising
10.2
11.42
12.5
V
22
23
23.8
V
Classification Stability Time
Classification Current
2
ICLASS
VDD = 12.6V
to 20V
ms
CLASS2 = GND
9.12
10.5
11.88
CLASS2 = VDRV
16.1
18
20.9
mA
POWER MODE
VDD Supply Voltage Range
VDD Supply Current
www.maximintegrated.com
VDD
IDD
VDD = 60V
3.3
60
V
4.5
mA
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)
(VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +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 OnResistance
SYMBOL
VON
VOFF
VHYST_UVLO
tOFF_DLY
tDELAY
RON_ISO
CONDITIONS
VDD rising
VDD falling
MIN
TYP
MAX
UNITS
37.2
38.8
40
V
30
31.5
V
(Note 6)
7.3
V
VDD falling from 40V to 20V
(Note 5)
150
μs
tDELAY = time after (VDD - VCC)
from 1.5V to 0V
123
ms
IVCC = 100mA
TJ = +25°C
TJ = +85°C
1.2
ω
1.5
MAINTAIN POWER SIGNATURE (MPS = VDRV)
PoE MPS Current Rising
Threshold
IMPS_RISE
18
28.7
40
mA
PoE MPS Current Falling
Threshold
IMPS_FALL
14
24
35
mA
PoE MPS Current Threshold
Hysteresis
IMPS_HYS
4.3
mA
PoE MPS Output Average
Current
IMPS_AVE
4.8
mA
12.6
mA
PoE MPS Peak Output Current
IMPS_PEAK
10
PoE MPS Time High
IMPS_HIGH
95
ms
PoE MPS Time Low
IMPS_LOW
190
ms
CURRENT LIMIT
Inrush Current Limit
Current Limit During Normal
Operation
IINRUSH
During initial turn-on period,
VDD - VCC = 4V, measured at VCC
39
49
60
mA
ILIM
After inrush completed, VCC = VDD
- 1.5V, measured at VCC
290
321
360
mA
8.8
V
LOGIC
WAD Detection Rising Threshold
VWAD_RISE
WAD Detection Falling Threshold
VWAD_FALL
5.8
WAD Detection Hysteresis
WAD Input Current
CLASS2, MPS Voltage Rising
Threshold
www.maximintegrated.com
IWAD
VCLASS2, RISE
VWAD = 24V
V
0.6
V
125
μA
2.9
V
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)
(VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
CLASS2, MPS Voltage Falling
Threshold
RESET Output Voltage Low
SYMBOL
CONDITIONS
VCLASS2, FALL
VOL_RESET
MIN
TYP
MAX
0.4
UNITS
V
ISINK = 1mA
0.2
V
-10
+10
μA
Inferred from VAUX input current
4.75
14
V
VAUX from 4.75V to 14V
0.65
3.1
mA
4.2
5.5
V
VWK falling and VULP rising and
falling
1.6
2.9
V
SL Logic Threshold
Falling
0.55
0.8
V
SL Current
VSL = 0V
RSL = 60.4kω, VLED = 6.5V
9.2
10.6
12
19.2
21.2
23.5
mA
20
mA
31.4
mA
RESET, CLASS2, MPS Leakage
ILOG_LEAK
INTERNAL REGULATOR WITH BACK BIAS
VAUX Input Voltage Range
VAUX Input Current
VAUX
IAUX
VDRV Output Voltage
SLEEP MODE
WK and ULP Logic Threshold
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
VTH
ILED
RSL = 30.2kω, VLED = 6.5V
RSL = 30.2kω, VLED = 3.5V
IRANGE
ILED_MAX
fILED
DILED
IVDD
62.4
μA
21.2
10
VSL = 0V
Sleep and ultra-low-power modes
20.6
Sleep and ultra-low-power modes
Sleep mode, VLED = 6.5V
26
250
Hz
25
10
%
12
14.5
mA
DIVDD
tMP_ENABLE
Sleep and ultra-low-power modes
Internal Current Enable Time
Ultra-low-power mode
76
75
88
98
ms
%
Internal Current Disable Time
tMP_DISABLE
Ultra-low-power mode
205
237
265
ms
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
TSD
TSD,HYS
TJ rising
151
°C
16
°C
LDO
Input Voltage Range
Inferred from line regulation
Output Voltage
LDO_FB = VDRV
Max Output Voltage Setting
With external divider to LDO_FB
LDO FB Regulation Voltage
www.maximintegrated.com
4.5
14
3.3
1.2
V
V
1.227
5.5
V
1.25
V
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)
(VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
LDO FB Leakage Current
MIN
TYP
-1
MAX
UNITS
+1
μA
VLDO_IN = 5V, VLDO_FB = VDRV,
ILOAD = 80mA
300
mV
Load Regulation
ILOAD from 1mA to 80mA
0.5
mV/mA
Line Regulation
VLDO_IN from 4.5V to 14V
1.4
mV/V
Dropout
VDROPOUT
Overcurrent Protection
Threshold
IOVC
85
LDO_FB Rising Threshold
mA
3.3
LDO_FB Hysteresis
2.3
3.7
2.4
V
V
DC-DC CONVERTER INPUT SUPPLY
VDD Voltage Range
VDD,RISING
VDD,FALLING
VCC = VDD = VWAD - 0.3V, rising
VCC = VDD = VWAD - 0.3V, falling
WAD Detection Rising Threshold
VWAD,RISE
(Note 7)
WAD Detection Falling Threshold
VWAD,FALL
(Note 7)
8
60
7.7
60
8.8
5.8
WAD Detection Hysteresis
V
V
V
0.6
V
ILX = 0.5A (sourcing)
0.54
ω
ILX = 0.5A (sinking)
0.14
ω
POWER MOSFETs
High-Side pMOS On-Resistance
Low-Side nMOS On-Resistance
LX Leakage Current
RDSON-H
RDSON-L
ILX-LKG
VDD = VCC = 28V, VLX = (VPGND
+ 1V) to (VCC - 1V)
-5
+5
μA
SOFT-START (SS)
Soft-Start Time
tSS-TH
10
ms
FEEDBACK (FB)
FB Regulation Voltage
VFB-RG
FB Input Bias Current
IFB
1.203
VFB = 1.224V
1.226
1.252
V
10
200
nA
OUTPUT VOLTAGE
Output Voltage Range
Cycle-by-Cycle Overvoltage
Protection
www.maximintegrated.com
VOUT
VOUT-OV
MAX5988A
3.0
5.6
MAX5988B
5.4
14
Rising (Note 8)
100.5
103
108
Falling (Note 8)
98.5
101.1
104
V
%
Maxim Integrated │ 5
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Electrical Characteristics (continued)
(VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INTERNAL COMPENSATION NETWORK
Compensation Network ZeroResistance
RZERO
200
kω
Compensation Network ZeroCapacitance
CZERO
150
pF
CURRENT LIMIT
MAX5988A
Peak Current-Limit Threshold
IPEAK-LIMIT
MAX5988B
Runaway Current-Limit
Threshold
Valley Current-Limit Threshold
ZX Threshold
MAX5988A
IRUNAWAY-LIMIT
MAX5988B
IVALLEY-LIMIT
CLASS2 = GND
1.45
1.64
CLASS2 = VDRV
1.66
1.79
CLASS2 = GND
0.75
0.81
CLASS2 = VDRV
0.85
0.94
CLASS2 = GND
1.9
CLASS2 = VDRV
2.2
CLASS2 = GND
0.93
CLASS2 = VDRV
1.07
MAX5988A
1.5
MAX5988B
0.75
IZX
A
A
A
25
mA
TIMINGS
Switching Frequency
fSW
190
215
238
kHz
Frequency Foldback
fSW-FOLD
95
107.5
119
kHz
Consecutive ZX Events for
Entering Foldback
8
Events
Consecutive ZX Events for
Exiting Foldback
8
Events
VOUT Undervoltage Trip Level to
Cause HICCUP
VOUT-HICF
After soft-start completed (Note 8)
55
HICCUP Timeout
Minimum On-Time
60
65
154
tON-MIN
113
LX Dead Time
%
ms
140
14
ns
ns
RESET
VFB Threshold for RESET
Assertion
VFB-OKF
VFB falling (Note 8)
87
90
93
%
VFB Threshold for RESET
Deassertion
VFB-OKR
VFB rising (Note 8)
91.5
95
98
%
www.maximintegrated.com
Maxim Integrated │ 6
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Electrical Characteristics (continued)
(VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND,
C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected, CLASS2 = 0V, MPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
VLDO_FB Threshold for RESET
Assertion
SYMBOL
VLDO_FB-OKF
VLDO_FB Threshold for RESET
Deassertion
CONDITIONS
MIN
TYP
MAX
UNITS
VLDO_FB falling, LDO_FB = VDRV
(Note 9)
90
%
VFB rising
95
%
4.8
ms
RESET Deassertion Delay
3: All devices are 100% production tested at TA = +25°C. Limits over temperature are guaranteed by design.
4: The input offset current is illustrated in Figure 2.
5: Effective differential input resistance is defined as the differential resistance between VDD and GND, see Figure 2.
6: A 20V glitch on input voltage, which takes VDD below VON shorter than or equal to tOFF_DLY does not cause the device to
exit power-on mode.
Note 7: The WAD detection rising and falling thresholds control the isolation power MOS transistor. To turn the DC-DC on in WAD
mode, the WAD must be detected and the VDD must be within the VDD voltage range.
Note 8 Referred to feedback regulation voltage.
Note 9: Referred to LDO feedback regulation voltage.
Note
Note
Note
Note
IIN
RTEST
dRi =
1V
(VINi + 1 - VINi)
=
(IINi + 1 - IINi) (IINi + 1 - IINi)
IOFFSET = IINi 1ms/10ms/100ms
100V
MAX5988A
IINi + 1
EVALUATION
BOARD
IINi
VINi
dRi
dRi
IOFFSET
VINi
Figure 1. MAX5988A–MAX5988D Internal TVS Test Setup
www.maximintegrated.com
1V
VINi + 1
VIN
Figure 2. Effective Differential Resistance and Offset Current
Maxim Integrated │ 7
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
QUIESCENT CURRENT vs. SUPPLY
VOLTAGE (ULTRA-LOW POWER MODE)
0.35
0.30
0.25
0.20
0.15
0.10
3.50
3.25
3.00
2.75
0
2.9
4.4
5.9
7.4
8.9
2.50
10.1
27
26
25
24
23
22
40
35
45
50
55
1.4
60
2.9
4.4
5.9
7.4
8.9
INPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
INPUT OFFSET CURRENT
vs. INPUT VOLTAGE
CLASSIFICATION CURRENT
vs. INPUT VOLTAGE
CLASSIFICATION SETTLING TIME
MAX5988A toc04
3
2
1
0
-1
-2
25
23
CLASSIFICATION CURRENT (mA)
1.4
28
MAX5988A toc03
3.75
0.05
OFFSET CURRENT (µA)
MAX5988A toc02
0.40
4.00
21
CLASS2
19
10.1
MAX5988A toc06
MAX5988A toc05
DETECTION CURRENT (mA)
0.45
QUIESCENT CURRENT (mA)
MAX5988A toc01
0.50
SIGNATURE RESISTANCE
vs. SUPPLY VOLTAGE
DIFFERENTIAL RESISTANCE (kI)
DETECTION CURRENT vs. INPUT VOLTAGE
VDD
10V/div
GND
17
15
13
CLASS1
11
IDD
10mA /div
0mA
9
7
-3
5
4.4
5.9
7.4
8.9
10.1
10
12
SUPPLY VOLTAGE (V)
16
18
20
22
24
INRUSH CURRENT LIMIT vs. VCC VOLTAGE
LED CURRENT vs. R SL
44
20
20
18
8
6
12
18
24
VCC (V)
Maxim Integrated
www.maximintegrated.com
30
36
42
48
15
RSL = 60.4kI
10
12
40
RSL = 30.2kI
LED CURRENT (mA)
48
25
MAX5988A toc08
24
LED CURRENT (mA)
52
LED CURRENT vs. LED VOLTAGE
28
MAX5988A toc07
56
0
400µs/div
INPUT VOLTAGE (V)
60
INRUSH CURRENT (mA)
14
MAX5988A toc09
2.9
1.4
10
20
30
40
50
RSL (kI)
60
70
80
5
0
1.75
3.50
5.25
7.00
LED VOLTAGE (V)
8
Maxim Integrated │ 8
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
VIN = 36V
EFFICIENCY (%)
90
90
85
80
VIN = 48V
75
VIN = 36V
VIN = 48V
95
EFFICIENCY (%)
VIN = 12V
95
100
MAX5988A toc10
100
EFFICIENCY vs. LOAD CURRENT
(MAX5988B, VOUT = 12V)
MAX5988A toc11
EFFICIENCY vs. LOAD CURRENT
(MAX5988A, VOUT = 5V)
VIN = 57V
80
75
70
70
65
65
60
VIN = 57V
85
60
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
0.1
0.2
0.3
0.4
0.5
LOAD CURRENT (A)
LOAD CURRENT (A)
5V LOAD TRANSIENT
(0% TO 50%)
5V LOAD TRANSIENT
(50% TO 100%)
MAX5988A toc12
0.6
MAX5988A toc13
VOUT
AC-COUPLED
50mV/div
VOUT
AC-COUPLED
50mV/div
IOUT
500mA /div
0A
IOUT
500mA /div
0A
100µs/div
100µs/div
DC-DC CONVERTER STARTUP
IOUT = 0A
DC-DC CONVERTER STARTUP
ROUT = 6.67I
MAX5988A toc14
2ms/div
Maxim Integrated
www.maximintegrated.com
0.7
MAX5988A toc15
VOUT
1V/div
VOUT
1V/div
VGND
VGND
2ms/div
9
Maxim Integrated │ 9
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Pin Configuration
WK
LDO_FB
RESET
MPS
CLASS2
TOP VIEW
15
14
13
12
11
WAD 16
10
ULP
VDD 17
9
SL
8
VDRV
7
GND
6
FB
MAX5988A
MAX5988B
VCC 18
PGND 19
4
5
LDO_OUT
3
LDO_IN
1
AUX
2
LED
+
LX
RREF 20
*EP
TQFN
4mm × 4mm
*EXPOSED PAD, CONNECT EP TO GND.
Pin Description
PIN
NAME
1
AUX
2
LX
3
LED
LED Driver Output. In sleep mode, LED sources a periodic current (ILED) at 250Hz with 25% duty
cycle.
4
LDO_IN
LDO Input Voltage. Connect LDO_IN to output when used; otherwise, connect to GND. Connect a
minimum 1FF bypass capacitor between LDO_IN and GND.
5
LDO_OUT
6
FB
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FUNCTION
Auxiliary Voltage Input. Auxiliary input to the internal regulator, VDRV. Connect AUX to the output of
the buck converter, if the output voltage is greater than 4.75V, to back bias the internal circuitry and
increase efficiency. Connect to a clean ground when not used.
Inductor Connection. Inductor connection for the internal DC-DC converter.
LDO Output Voltage. Connect a minimum 1FF output capacitor between LDO_OUT and GND.
Feedback. Feedback input for the DC-DC buck converter. Connect FB to a resistive divider from the
output to GND to adjust the output voltage.
Maxim Integrated │ 10
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Pin Description (continued)
PIN
NAME
FUNCTION
7
GND
Ground. Reference rail for the device. It is also the “quiet” ground for all voltage references (e.g., FB is
referenced to this GND).
8
VDRV
Internal 5V Regulator Voltage Output. The internal voltage regulator provides 5V to the MOSFET driver
and other internal circuits. VDRV is referenced to GND. Do not use VDRV to drive external circuits.
Connect a 1FF bypass capacitor between VDRV and GND.
9
SL
Sleep Mode Enable Input. A falling edge on SL brings the device into sleep mode. An external resistor
(RSL) connected between SL and GND sets the LED current (ILED).
10
ULP
Ultra-Low Power-Mode Enable Input. ULP has an internal 50kω pullup resistor to the internal 5V bias
rail. A falling edge on SL while ULP is asserted low enables ultra-low power mode. When ultra-low
power mode is enabled, the power consumption of the device is reduced even lower than sleep mode
to comply with ultra-low power sleep power requirements while still supporting MPS.
11
CLASS2
Class 2 Selection Pin. Connect to VDRV for Class 2 operation. Connect to GND for Class 1 operation.
12
MPS
13
RESET
14
LDO_FB
15
WK
MPS Enable Pin. Connect to VDRV to turn the MPS function on. Connect to GND to turn the MPS
function off.
Open-Drain RESET Output. The RESET output is driven low if either LDO_OUT or FB drops below
90% of its set value. RESET goes high 4.8ms after both LDO_OUT and FB rise above 95% of their set
values. Leave unconnected when not used.
LDO Regulator Feedback Input. Connect to VDRV to get the preset LDO output voltage of 3.3V, or
connect to a resistive divider from LDO_OUT to GND for an adjustable LDO output voltage.
Wake Mode Enable Input. WK has an internal 50kω pullup resistor to the internal 5V bias rail. A falling
edge on WK brings the device out of sleep mode and into the normal operating mode (wake mode).
16
WAD
Wall Power Adapter Detector Input. Wall adapter detection is enabled when the voltage from WAD
to GND is greater than 8.8V. When a wall power adapter is present, the isolation p-channel power
MOSFET turns off. Connect WAD through a 10kω resistor to GND when the wall power adapter or other
auxiliary power source is not used.
17
VDD
Positive Supply Input. Connect a 68nF (min) bypass capacitor between VDD and PGND.
18
VCC
DC-DC Converter Power Input. VDD is connected to VCC by an isolation p-channel MOSFET. Connect a
10FF capacitor in parallel with a 1FF ceramic capacitor between VCC and PGND.
19
PGND
Power Ground. Power ground of the DC-DC converter power stage. Connect PGND to GND with a star
connection. Do not use PGND as reference for sensitive feedback circuit.
20
RREF
Signature Resistor Connection. Connect a 24.9kω resistor (RSIG) to GND.
—
EP
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Exposed Pad. Connect the exposed pad to GND.
Maxim Integrated │ 11
MAX5988A/MAX5988B
Detailed Description
PD Interface
The MAX5988A/MAX5988B include complete interface
functions for a PD to comply with the IEEE 802.3af standard as a Class 1/Class 2 PD. The devices provide the
detection and classification signatures using a single
external signature resistor. An integrated MOSFET provides isolation from the buck converter when the PSE has
not applied power. The devices guarantee a leakage current offset of less than 10µA during the detection phase.
The devices feature power-mode undervoltage-lockout
(UVLO) with wide hysteresis and long deglitch time to
compensate for twisted-pair-cable resistive drop and to
ensure glitch-free transitions between detection, classification, and power-on/-off modes.
Operating Modes
The devices operate in three different modes depending
on VDD. The three modes are detection mode, classification mode, and power mode. The device is in detection
mode when VDD is between 1.4V and 10.1V, classification mode when VDD is between 12.6V and 20V, and
power mode when the input voltage exceeds VON.
Detection Mode (1.4V < VDD < 10.1V)
In detection mode, the devices provide a signature
differential resistance to VDD. During detection, the
power-sourcing equipment (PSE) applies two voltages to
VDD, both between 1.4V and 10.1V with a minimum 1V
increment. The PSE computes the differential resistance
to ensure the presence of the 24.9kω signature resistor. Connect the 24.9kω signature resistor (RSIG) from
RREF to GND for proper signature detection. The device
applies VDD to RREF when in detection mode, and the
VDD offset current due to the device is less than 10µA.
The DC offset due to protection diodes does not significantly affect the signature resistance measurement.
Classification Mode (12.6V < VDD < 20V)
In classification mode, the devices sink Class 1/Class 2
classification currents. The PSE applies a classification
voltage between 12.6V and 20V, and measures the classification currents. The devices use the external 24.9kω
resistor (RSIG) and the CLASS2 pin to set the classifi-
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IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
cation current at 10.5mA (Class 1, CLASS1 = GND) or
18mA (Class 2, CLASS2 = VDRV). The PSE uses this to
determine the maximum power to deliver. The classification current includes current drawn by the supply current
of the device so the total current drawn by the PD is within the IEEE 802.3af standard. The classification current
is turned off when the device leaves classification mode.
Power Mode (VDD > VON)
In power mode, the devices have the isolation MOSFET
between VDD and VCC fully on. The devices have the
buck regulator enabled and the LDO enabled. The
devices can be in either wake mode, sleep mode, or
ultra-low-power mode. The buck regulator and LDO are
only enabled in wake mode.
The devices enter power mode when VDD rises above
the undervoltage lockout threshold (VON). When VDD
rises above VON, the device turns on the internal p-channel isolation MOSFET to connect VCC to VDD with inrush
current limit internally set to 49mA (typ). The isolation
MOSFET is fully turned on when VCC is near VDD and the
inrush current is below the inrush limit. Once the isolation MOSFET is fully turned on, the device changes the
current limit to 321mA (typ). The buck converter turns on
123ms after the isolation MOSFET turns on fully.
Undervoltage Lockout
The devices operate with up to a 60V supply voltage
with a turn-on UVLO threshold (VON) at 38.8V (typ), and
a turn-off UVLO threshold (VOFF) at 31.5V (typ). When
the input voltage is above VON, the device enters power
mode and the internal isolation MOSFET is turned on.
When the input voltage is below VOFF for more than
tOFF_DLY, the MOSFET and the buck converter are off.
LED Driver
The devices drive an LED, or multiple LEDs in series, with
a maximum LED voltage of 6.5V. In sleep mode and ultralow-power mode, the LED current is pulse width modulated with a duty cycle of 25% and the amplitude is set by
R SL. The LED driver current amplitude is programmable
from 10mA to 20mA using R SL according to the formula:
ILED = 646/R SL (mA)
where R SL is in kω.
Maxim Integrated │ 12
MAX5988A/MAX5988B
Sleep and Ultra-Low-Power Modes
The devices feature a sleep mode and an ultra-lowpower mode in which the internal p-channel isolation
MOSFET is kept on and the buck regulator is off. In sleep
mode, the LED driver output (LED) pulse width modulates the LED current with a 25% duty cycle. The peak
LED current (ILED) is set by an external resistor R SL. To
enable sleep mode, apply a falling edge to SL with ULP
disconnected or high impedance. Sleep mode can only
be entered from wake mode.
Ultra-low-power mode allows the devices to reduce
power consumption lower than sleep mode, while maintaining the power signature of the IEEE standard. The
ultra-low-power-mode enable input ULP is internally held
high with a 50kω pullup resistor to the internal 5V bias of
the device. To enable ultra-low-power mode, apply a falling edge to SL with ULP = LOW. Ultra-low-power mode
can only be entered from wake mode.
To exit from sleep mode or ultra-low-power mode and
resume normal operation, apply a falling edge on the
wake-mode enable input (WK).
Thermal-Shutdown Protection
If the devices’ die temperature reaches 151°C, an overtemperature fault is generated and the device shuts
down. The die temperature must cool down below
+135°C to remove the overtemperature fault condition.
After a thermal shutdown condition clears, the device is
reset.
WAD Description
For applications where an auxiliary power source such
as a wall power adapter is used to power the PD, the
devices feature wall power adapter detection.
The wall power adapter is connected from WAD to PGND.
The devices detect the wall power adapter when the voltage from WAD to PGND is greater than 8.8V. When a wall
power adapter is detected, the internal isolation MOSFET
is turned off, classification current is disabled.
Connect the auxiliar power source to WAD, connect a
diode from WAD to VDD, and connect a diode from WAD
to VCC. See the typical application circuit in Figures 3
and 4.
www.maximintegrated.com
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
The application circuit must ensure that the auxiliary
power source can provide power to VDD and VCC by
means of external diodes. The voltage on VDD must be
within the VDD voltage range to allow the DC-DC to operate. To allow operation of the DC-DC converter, the VDD
and VCC voltage must be greater than 8V, on the rising
edge, while on the falling edge the VDD and VCC may fall
down to 7.7V keeping the DC-DC converter on.
Note: When operating solely with a wall power adapter,
the WAD voltage must be able to meet the condition VDD
> 8.8V, that likely results in WAD > 8.8V.
Internal Linear Regulator and Back Bias
An internal voltage regulator provides VDRV to internal
circuitry. The VDRV output is filtered by a 1µF capacitor connected from VDRV to GND. The regulator is for
internal use only and cannot be used to provide power to
external circuits. VDRV can be powered by either VDD or
VAUX, depending on VAUX. The internal regulator is used
for both PD and buck converter operations.
VOUT can be used to back bias the VDRV voltage regulator if VOUT is greater than 4.75V. Back biasing VDRV
increases device efficiency by drawing current from
VOUT instead of VDD. If VOUT is used as back bias,
connect AUX directly to VOUT. In this configuration, the
VDRV source switches from VDD to VAUX after the buck
converter’s output has reached its regulation voltage.
Cable Discharge Event Protection (CDE)
A 70V voltage clamp is integrated to protect the internal
circuits from a cable discharge event.
DC-DC Buck Converter
The DC-DC buck converter uses a PWM, peak currentmode, fixed-frequency control scheme providing an
easy-to-implement architecture without sacrificing a fast
transient response. The buck converter operates in a
wide input voltage range from 8.8V to 60V and supports
up to 6.49W of output power at 1.3A load. The devices
provide a wide array of protection features including
UVLO, overtemperature shutdown, short-circuit protection with hiccup runaway current limit, cycle-by-cycle
peak current protection, and cycle-by-cycle output overvoltage protection, for enhanced performance and reliability. A frequency foldback scheme is implemented to
reduce the switching frequency to half at light loads to
increase the efficiency.
Maxim Integrated │ 13
MAX5988A/MAX5988B
Frequency Foldback Protection for
High-Efficiency Light-Load Operation
The devices enter frequency foldback mode when eight
consecutive inductor current zero-crossings occur. The
switching frequency is 215kHz under loads large enough
that the inductor current does not cross zero. In frequency foldback mode, the switching frequency is reduced to
107.5kHz to increase power conversion efficiency. The
device returns to normal mode when the inductor current
does not cross zero for eight consecutive switching periods. Frequency foldback mode is forced during startup
until 50% of the soft-start is completed.
Hiccup Mode
The devices include a hiccup protection feature. When
hiccup protection is triggered, the devices turn off the
high-side and turn on the low-side MOSFET until the
inductor current reaches the valley current limit. The
control logic waits 154ms until attempting a new softstart sequence. Hiccup mode is triggered if the current
in the high-side MOSFET exceeds the runaway currentlimit threshold, both during soft-start and during normal
operating mode. Hiccup mode can also be triggered in
normal operating mode in the case of an output undervoltage event. This happens if the regulated feedback
voltage drops below 60% (typ).
RESET Output
The devices feature an open-drain RESET output that
indicates if either the LDO or the switching regulator drop
out of regulation. The RESET output goes low if either
regulator drops below 90% of its regulated feedback
value. RESET goes high impedance 4.8ms after both
regulators are above 95% of their value.
Maintain Power Signature (MPS)
The devices feature the MPS to comply with the IEEE
802.3af standard. It is able to maintain a minimum current
(10mA) of the port to avoid the power disconnection from
the PSE. The devices enter MPS mode when the port
current is lower than 14mA and also exit the MPS mode
when the port current is greater than 40mA. The feature is
enabled by connecting the MPS pin to VDRV, or disabled
by connecting the MPS pin to GND.
Applications Information
Operation with Wall Adapter
For applications where an auxiliary power source such
as a wall power adapter is used to power the PD, the
devices feature wall power adapter detection. The device
www.maximintegrated.com
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
gives priority to the WAD supply over VDD supply, and
smoothly switches the power supply to WAD when it is
detected. The wall power adapter is connected from
WAD to PGND. The devices detect the wall power adapter when the voltage from WAD to PGND is greater than
8.8V. When a wall power adapter is detected, the internal
isolation MOSFET is turned off, classification current is
disabled and the device draws power from the auxiliary
power source through VCC. Connect the auxiliary power
source to WAD, connect a diode from WAD to VCC. See
the typical application circuit in Figures 3 and 4.
Adjusting LDO Output Voltage
An uncommitted LDO regulator is available to provide
a supply voltage to external circuits. A preset voltage
of 3.3V is set by connecting LDO_FB directly to VDRV.
For different output voltages connect a resistor divider
from LDO_OUT and LDO_FB to GND. The total feedback resistance should be in the range of 100kω. The
minimum output current capability is 85mA and thermal
considerations must be taken to prevent triggering thermal shutdown. The LDO regulator can be powered by
VOUT, a different power supply, or grounded when not
used. The LDO is enabled once the buck converter has
reached the regulation voltage. The LDO is disabled
when the buck converter is turned off or not regulating.
Adjusting Buck Converter Output Voltage
The buck converter output voltage is set by changing
the feedback resistor-divider ratio. The output voltage
can be set from 3.0V to 5.6V (MAX5988A) or 5.4V to
14V (MAX5988B). The FB voltage is regulated to 1.227V.
Keep the trace from the FB pin to the center of the resistive divider short, and keep the total feedback resistance
around 10kω.
Inductor Selection
Choose an inductor with the following equation:
L=
VOUT × (VCC − VOUT )
fS × VCC × L IR × IOUT(MAX)
where LIR is the ratio of the inductor ripple current to
full load current at the minimum duty cycle. Choose LIR
between 20% to 40% for best performance and stability.
Use an inductor with the lowest possible DC resistance
that fits in the allotted dimensions. Powdered iron ferrite
core types are often the best choice for performance.
With any core material, the core must be large enough
not to saturate at the current limit of the devices.
Maxim Integrated │ 14
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
VCC Input Capacitor Selection
The input capacitor reduces the current peaks drawn
from the input power supply and reduces switching noise
in the IC. The total input capacitance must be equal or
greater than the value given by the following equation
to keep the input-ripple voltage within specification and
minimize the high-frequency ripple current being fed
back to the input source:
CIN_MIN =
VRIPPLE(C) =
VRIPPLE(ESL)
=
IP − P
× ESL
t ON
or
The impedance of the input capacitor at the switching
frequency should be less than that of the input source so
high-frequency switching currents do not pass through
the input source, but are instead shunted through the
input capacitor. The input capacitor must meet the ripple
current requirement imposed by the switching currents.
The RMS input ripple current is given by:
VOUT × (VCC
IP − P
8 × C OUT × fS
VRIPPLE(ESR)
= IP −P × ESR
D × TS × IOUT
VIN−RIPPLE
where VIN-RIPPLE is the maximum allowed input ripple
voltage across the input capacitors and is recommended
to be less than 2% of the minimum input voltage. D is the
duty cycle (VOUT/VIN) and TS is the switching period (1/fS).
IRIPPLE
= ILOAD ×
where the output ripple due to output capacitance, ESR,
and ESL is:
VOUT )
IN
where IRIPPLE is the input RMS ripple current.
Output Capacitor Selection
The key selection parameters for the output capacitor are
capacitance, ESR, ESL, and voltage-rating requirements.
These affect the overall stability, output ripple voltage,
and transient response of the DC-DC converter. The output ripple occurs due to variations in the charge stored in
the output capacitor, the voltage drop due to the capacitor’s ESR, and the voltage drop due to the capacitor’s
ESL. Estimate the output-voltage ripple due to the output
capacitance, ESR, and ESL:
VRIPPLE(ESL)
=
IP − P
× ESL
t OFF
or whichever is larger. The peak-to-peak inductor current
(IP-P)
=
IP −P
VCC − VOUT
V
× OUT
fS × L
VCC
Use these equations for initial output capacitor selection. Determine final values by testing a prototype or an
evaluation circuit. A smaller ripple current results in less
output-voltage ripple. Since the inductor ripple current is
a factor of the inductor value, the output-voltage ripple
decreases with larger inductance. Use ceramic capacitors for low ESR and low ESL at the switching frequency
of the converter. The ripple voltage due to ESL is negligible when using ceramic capacitors.
Load-transient response depends on the selected output
capacitance. During a load transient, the output instantly
changes by ESR x ILOAD. Before the controller can
respond, the output deviates further, depending on the
inductor and output capacitor values. After a short time,
the controller responds by regulating the output voltage
back to its predetermined value. The controller response
time depends on the closed-loop bandwidth. A higher
bandwidth yields a faster response time, preventing the
output from deviating further from its regulating value.
VRIPPLE = VRIPPLE(C) + VRIPPLE(ESR) +VRIPPLE(ESL)
Table 1. Design Selection Table
CIN
COUT
OUTPUT
(V)
CERAMIC
ELECTROLYTIC
CERAMIC
3.3
2.2FF/100V
10FF/63V
1 x 100FF/6.3V
33FH/1.4A
1
5
2.2FF/100V
10FF/63V
1 x 100FF/6.3V
47FH/1.6A
1 or 2
12
2.2FF/100V
10FF/63V
2 x 10FF/16V
220FH/0.8A
1 or 2
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L
CLASS
Maxim Integrated │ 15
MAX5988A/MAX5988B
PCB Layout
Careful PCB layout is critical to achieve clean and stable
operation. It is highly recommended to duplicate the
MAX5988A EV kit layout for optimum performance. If
deviation is necessary, follow these guidelines for good
PCB layout:
1)Connect input and output capacitors to the power
ground plane; connect all other capacitors to the signal ground plane.
2)Place capacitors on VDD, VCC, AUX, VDRV as close
as possible to the IC and its corresponding pin using
direct traces. Keep power ground plane (connected
to PGND) and signal ground plane (connected to
GND) separate.
3)Keep the high-current paths as short and wide as
possible. Keep the path of switching current short
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IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
and minimize the loop area formed by LX, the output
capacitors, and the input capacitors.
4)Connect VDD, VCC, and PGND separately to a large
copper area to help cool the IC to further improve
efficiency and long-term reliability.
5)Ensure all feedback connections are short and direct.
Place the feedback resistors and compensation components as close as possible to the IC.
6)Route high-speed switching nodes, such as LX, away
from sensitive analog areas (FB).
7) Place enough vias in the pad for the EP of the devices
so that heat generated inside can be effectively dissipated by the PCB copper. The recommended spacing for the vias is 1mm to 1.2mm pitch. The thermal
vias should be plated (1oz copper) and have a small
barrel diameter (0.3mm to 0.33mm).
Maxim Integrated │ 16
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Typical Application Circuits
RJ45 AND
BRIDGE
RECTIFIER
C1
68nF
2.2µF
VDD
C2
10µF
VCC
WAD
AUX
VDRV
L0
47µH
CLASS2
C3
1µF
LDO_FB
WK
TO µP OPEN-DRAIN OUTPUTS
OR PULLDOWN SWITCHES
R1
7.5kI
MAX5988A
MAX5988B
ULP
C4
100µF
FB
SL
R2
2.49kI
RSL
60.4kI
TO 5V OUTPUTS
5V
OUTPUT
LX
MPS
LDO_IN
LDO_OUT
C5
1µF
C6
1µF
LED
RREF
RSIG
24.9kI
3.3V
OUTPUT
GND
PGND
0I
Figure 3. MAX5988A/MAX5988B Buck Regulator and Fixed LDO Output
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Maxim Integrated │ 17
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Typical Application Circuits (continued)
RJ45 AND
BRIDGE
RECTIFIER
C1
68nF
2.2µF
VDD
C2
10µF
VCC
WAD
AUX
VDRV
L0
47µH
CLASS2
C3
1µF
R1
7.5kI
MAX5988A
MAX5988B
WK
TO µP OPEN-DRAIN OUTPUTS
OR PULLDOWN SWITCHES
5V
OUTPUT
LX
MPS
ULP
C4
100µF
FB
R2
2.49kI
SL
RSL
60.4kI
ADJ_LDO_OUT
LDO_OUT
R3
TO 5V OUTPUTS
LDO_IN
R4
RREF
RSIG
24.9kI
C6
1µF
LDO_FB
C5
1µF
LED
GND
PGND
0I
Figure 4. MAX5988A/MAX5988B Buck Regulator and Adjustable LDO Output
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Maxim Integrated │ 18
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Functional Diagram
MAX5988A
MAX5988B
VCC
VDD
5V
TVS
HOT-SWAP
CONTROLLER
DETECTION
CLASSIFICATION
GND
5V
RREF
WAD
PD VOLTAGE
MONITOR
AUX
5V
5V
1.5V
5V
REGULATOR
VDRV
1
5V
0
CLK
BANDGAP
CONTROL
LX
DRIVER
VREF
LDO_IN
LDO_OUT
VREF
LDO
PGND
FB
LDO_FB
OPEN DRAIN
VDD
CLASS2
RESET
5V
VDD
50kI
CLASS
50kI
WK
MPS
MPS
LOGIC
SL
ULP
LED
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Maxim Integrated │ 19
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Chip Information
Package Information
PROCESS: BiCMOS
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
20 TQFN-EP
T2044+4
21-0139
90-0409
Ordering Information/Selector Guide
PART
PIN-PACKAGE
SLEEP/ULP
MODE
LDO
UVLO (V)
RESET
MPS/CLASS2
OUTPUTADJ
(V)
MAX5988AETP+
20 TQFN-EP*
Yes
Yes
38.8
Yes
Yes
3 to 5.6
MAX5988BETP+
20 TQFN-EP*
Yes
Yes
38.8
Yes
Yes
5.4 to 14
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
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Maxim Integrated │ 20
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Revision History
REVISION
NUMBER
REVISION
DATE
0
11/12
Initial release
—
1
1/13
Corrected land pattern number
20
2
4/14
Updated pin 16 in Pin Description table
11
3
1/15
Updated Benefits and Features section
1
DESCRIPTION
PAGES
CHANGED
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. │ 21
MAX5988A/MAX5988B
www.maximintegrated.com
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Maxim Integrated │ 22
MAX5988A/MAX5988B
www.maximintegrated.com
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, Powered Devices
with Integrated DC-DC Converter
Maxim Integrated │ 23
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