Datasheet

6Maxim 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
INTERNAL COMPENSATION NETWORK
Compensation Network Zero-
Resistance
R
ZERO
200 kω
Compensation Network Zero-
Capacitance
C
ZERO
150 pF
CURRENT LIMIT
Peak Current-Limit Threshold I
PEAK-LIMIT
MAX5988A
CLASS2 = GND 1.45 1.64
A
CLASS2 = VDRV 1.66 1.79
MAX5988B
CLASS2 = GND 0.75 0.81
CLASS2 = VDRV 0.85 0.94
Runaway Current-Limit
Threshold
I
RUNAWAY-LIMIT
MAX5988A
CLASS2 = GND 1.9
A
CLASS2 = VDRV 2.2
MAX5988B
CLASS2 = GND 0.93
CLASS2 = VDRV 1.07
Valley Current-Limit Threshold I
VALLEY-LIMIT
MAX5988A 1.5
A
MAX5988B 0.75
ZX Threshold I
ZX
25 mA
TIMINGS
Switching Frequency f
SW
190 215 238 kHz
Frequency Foldback f
SW-FOLD
95 107.5 119 kHz
Consecutive ZX Events for
Entering Foldback
8 Events
Consecutive ZX Events for
Exiting Foldback
8 Events
V
OUT
Undervoltage Trip Level to
Cause HICCUP
V
OUT-HICF
After soft-start completed (Note 8) 55 60 65 %
HICCUP Timeout 154 ms
Minimum On-Time t
ON-MIN
113 140 ns
LX Dead Time 14 ns
RESET
V
FB
Threshold for RESET
Assertion
V
FB-OKF
V
FB
falling (Note 8) 87 90 93 %
V
FB
Threshold for RESET
Deassertion
V
FB-OKR
V
FB
rising (Note 8) 91.5 95 98 %