Rainbow Electronics MAX17008 User Manual

Page 34

MAX17007A/MAX17008

3) Group the gate-drive components (BST capacitors,

bypass capacitor) together near the controller IC.

4) Make the DC-DC controller ground connections as

shown in Figures 1 and 2. This diagram can be
viewed as having four separate ground planes: I/O
ground, where all the high-power components go;
the power ground plane, where the PGND pin and
V

bypass capacitor go; the master’s analog

ground plane where sensitive analog components,
the master’s GND pin, and V

bypass capacitor

go; and the slave’s analog ground plane where the
slave’s GND pin and V

bypass capacitor go. The

master’s GND plane must meet the PGND plane
only at a single point directly beneath the IC.

Similarly, the slave’s GND plane must meet the
PGND plane only at a single point directly beneath
the IC. The respective master and slave ground
planes should connect to the high-power output
ground with a short metal trace from PGND to the
source of the low-side MOSFET (the middle of the
star ground). This point must also be very close to
the output capacitor ground terminal.

5) Connect the output power planes (V

OUT

and sys-

tem ground planes) directly to the output filter
capacitor positive and negative terminals with multi-
ple vias. Place the entire DC-DC converter circuit as
close to the load as is practical. See Figure 15.

Dual and Combinable QPWM Graphics
Core Controllers for Notebook Computers

______________________________________________________________________________________

OUTPUT 1

SMPS1

OUT1

OUT2

IN1

IN2

SMPS2

OUTPUT 2

KELVIN SENSE VIAS

UNDER THE INDUCTOR

(SEE MAX17007A EVALUATION KIT)

VIA TO POWER

GROUND

BYPASS

CAPACITOR

REF BYPASS
CAPACITOR

X-RAY VIEW.
IC MOUNTED
ON BOTTOM
SIDE OF PCB.

IC LAYOUT

CONNECT GND AND PGND THE
CONTROLLER AT ONE POINT
ONLY AS SHOWN

CONNECT THE

EXPOSED PAD TO

ANALOG GND

VIA TO ANALOG

GROUND

POWER STAGE LAYOUT (TOP SIDE OF PCB)

INDUCTOR

INPUT

POWER GROUND

INDUCTOR DCR SENSING

KELVIN SENSE VIAS TO

INDUCTOR PAD

CSL

CSH

Figure 15. PCB Layout Example