Datasheet

IEEE 802.3af/at-Compliant, Powered Device Interface
Controllers with Integrated 70W High-Power MOSFET
MAX5982A/MAX5982B/MAX5982C
14 _____________________________________________________________________________________
Applications Information
Operation with 12V Adapter
Layout Procedure
Careful PCB layout is critical to achieve high efficiency
and low EMI. Follow these layout guidelines for optimum
performance:
1) Place the input capacitor, classification resistor, and
transient voltage suppressor as close as possible to
the MAX5982A/MAX5982B/MAX5982C.
2) Use large SMT component pads for power dissipat-
ing devices such as the MAX5982A/MAX5982B/
MAX5982C and the external diodes.
3) Use short and wide traces for high-power paths.
4) Place enough vias in the pad for the EP of the
MAX5982A/MAX5982B/MAX5982C so that heat gen-
erated 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).
Figure 2. Typical Configuration When Using a 12V Wall Power Adapter
68nF
2-EVENT
CLASSIFICATION
(ASSERTED ON)
ENABLE
DC-DC
CONVERTER
IN+
IN-
RJ-45
AND
BRIDGE
RECTIFIER
GND
GND
-54V
SMAJ58A
MAX5982A
MAX5982B
MAX5982C
R
DET
24.9kI
R
CLS
V
DD
V
SS
RTN
WAD
PG
DET
CLS
2EC/WAD
2EC
12V
BATTERY
I.5mA
THIS CIRCUIT ACHIEVES
PROPER 2EC LOGIC WHEN
BATTERY IS < 12.5V
WALK MODE
INPUT
60.4kI
1kI
MAX5982A/MAX5982B ONLY
WK
SL
ULP
LED
-54V
-54V
-54V
ISOLATED SLEEP
MODE INPUT
ULTRA-LOW-POWER
SLEEP