Datasheet

10Maxim Integrated
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2,
Powered Devices with Integrated DC-DC Converter
Pin Description
Pin Configuration
PIN NAME FUNCTION
1 AUX
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.
2 LX Inductor Connection. Inductor connection for the internal DC-DC converter.
3 LED
LED Driver Output. In sleep mode, LED sources a periodic current (I
LED
) 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 LDO Output Voltage. Connect a minimum 1FF output capacitor between LDO_OUT and GND.
6 FB
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.
19
20
18
17
7
6
8
LX
LDO_OUT
9
AUX
LDO_FB MPS CLASS2 WK
12
V
CC
45
15 14 12 11
PGND
RREF
SL
VDRV
GND
FB
+
LED
RESET
3
13
V
DD
16
10
ULP
WAD
TQFN
4mm × 4mm
MAX5988A
MAX5988B
TOP VIEW
LDO_IN
*EXPOSED PAD, CONNECT EP TO GND.
*EP