Datasheet

3Maxim Integrated
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 SYMBOL CONDITIONS MIN TYP MAX UNITS
V
DD
Turn-On Voltage V
ON
V
DD
rising 37.2 38.8 40 V
V
DD
Turn-Off Voltage V
OFF
V
DD
falling 30 31.5 V
V
DD
Turn-On/Off Hysteresis V
HYST_UVLO
(Note 6) 7.3 V
V
DD
Deglitch Time t
OFF_DLY
V
DD
falling from 40V to 20V
(Note 5)
150 µs
Inrush to Operating Mode Delay t
DELAY
t
DELAY
= time after (V
DD
- V
CC
)
from 1.5V to 0V
123 ms
Isolation Power MOSFET On-
Resistance
R
ON_ISO
I
VCC
= 100mA
T
J
= +25°C 1.2
ω
T
J
= +85°C 1.5
MAINTAIN POWER SIGNATURE (MPS = VDRV)
PoE MPS Current Rising
Threshold
I
MPS_RISE
18 28.7 40 mA
PoE MPS Current Falling
Threshold
I
MPS_FALL
14 24 35 mA
PoE MPS Current Threshold
Hysteresis
I
MPS_HYS
4.3 mA
PoE MPS Output Average
Current
I
MPS_AVE
4.8 mA
PoE MPS Peak Output Current I
MPS_PEAK
10 12.6 mA
PoE MPS Time High I
MPS_HIGH
95 ms
PoE MPS Time Low I
MPS_LOW
190 ms
CURRENT LIMIT
Inrush Current Limit I
INRUSH
During initial turn-on period,
V
DD
- V
CC
= 4V, measured at V
CC
39 49 60 mA
Current Limit During Normal
Operation
I
LIM
After inrush completed, V
CC
= V
DD
- 1.5V, measured at V
CC
290 321 360 mA
LOGIC
WAD Detection Rising Threshold V
WAD_RISE
8.8 V
WAD Detection Falling Threshold V
WAD_FALL
5.8 V
WAD Detection Hysteresis 0.6 V
WAD Input Current I
WAD
V
WAD
= 24V 125 µA
CLASS2, MPS Voltage Rising
Threshold
V
CLASS2, RISE
2.9 V