Datasheet

16Maxim Integrated
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2,
Powered Devices with Integrated DC-DC Converter
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 sig-
nal ground plane.
2) Place capacitors on V
DD
, V
CC
, 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
and minimize the loop area formed by LX, the output
capacitors, and the input capacitors.
4) Connect V
DD
, V
CC
, 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 com-
ponents 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 dis-
sipated by the PCB copper. The recommended spac-
ing 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).