Rainbow-electronics MAX8720 Instrukcja Użytkownika Pobierz pdf (Strona 29)

Layout Procedure

1) Place the power components first, with ground ter-

minals adjacent (NL source, C

, C

OUT

, and DL

anode). If possible, make all these connections on

the top layer with wide, copper-filled areas.

2) Mount the controller IC adjacent to the low-side

MOSFET, preferably on the back side opposite NL

and NH to keep LX, GND, DH, and the DL gate-drive

lines short and wide. The DL and DH_ gate traces

must be short and wide (50 to 100 mils wide if the

MOSFET is 1in from the controller IC) to keep the dri-

ver impedance low and for proper adaptive dead-

time sensing.

3) Group the gate-drive components (BST diode and

capacitor, V

bypass capacitor) together near the

controller IC.

4) Make the DC-DC controller ground connections as

shown in Figures 1 and 12. This diagram can be

viewed as having two separate ground planes:

power ground, where all the high-power compo-

nents go, and an analog ground plane for sensitive

analog components. The analog ground plane and

power ground plane must meet only at a single point

directly at the IC.

5) Connect the output power planes directly to the out-

put filter capacitor positive and negative terminals

with multiple vias. Place the entire DC-DC converter

circuit as close to the load as is practical.

Chip Information

TRANSISTOR COUNT: 7190

PROCESS: BiCMOS

MAX8720

Dynamically Adjustable 6-Bit VID

Step-Down Controller

______________________________________________________________________________________ 29

BST

GND

SKIP

SUS

PGOOD

GNDS

ILIM

REF

TON

FBS

TIME

SHDN

V+

QSOP

TOP VIEW

MAX8720EEI

SUS

SKIP

TON

REF

36 35 34 33 32 31 30 29 28

10 11 12 13 14 15 16 17 18

PGND

N.C.

AGND

PGOOD

GNDS

ILIM

TIME

SHDN

V+

N.C.

BST

N.C.

THIN QFN

6mm x 6mm

MAX8720ETX

N.C.

FBS

Pin Configurations

1 2 ... 24 25 26 27 28 29 30 31

Step-Down Controller 1

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