Hig h -S p e e d , Dig it a lly Ad ju s t e d
S t e p -Do w n Co n t ro lle rs fo r No t e b o o k CP Us
where all the high-power components go; the PGND
La yo u t P ro c e d u re
1) Place the power components first, with ground termi-
nals adjacent (Q2 source, CIN-, COUT-, D1 anode). If
possible, make all these connections on the top layer
with wide, copper-filled areas.
plane, where the PGND pin and V bypass capaci-
DD
tor go; and an analog GND plane, where sensitive
analog components go. The analog ground plane
and PGND plane must meet only at a single point
directly beneath the IC. These two planes are then
connected to the high-power output ground with a
2) Mount the controller IC adjacent to MOSFET Q2,
preferably on the back side opposite Q2 in order to
keep LX-PGND current-sense lines and the DL gate-
drive line short and wide. The DL gate trace must be
short and wide, measuring 10 to 20 squares (50 to
100 mils wide if the MOSFET is 1 inch from the con-
troller IC).
short connection from V
cap/PGND to the source
DD
of the low-side MOSFET, Q2 (the middle of the star
ground). This point must also be very close to the out-
put capacitor ground terminal.
5) Connect the output power planes (V
and system
CORE
ground planes) directly to the output filter capacitor
positive and negative terminals with multiple vias.
Place the entire DC-DC converter circuit as close to
the CPU as is practical.
3) Group the gate-drive components (BST diode and
capacitor, V
bypass capacitor) together near the
DD
controller IC.
4) Make the DC-DC controller ground connections as
shown in Figure 11. This diagram can be viewed as
having three separate ground planes: output ground,
0/MAX71
P in Co n fig u ra t io n s
TOP VIEW
TOP VIEW
V+
SHDN
FB
1
2
3
4
5
6
7
8
9
24 DH
23 LX
22 BST
21 SKIP
20 D0
19 D1
18 D2
17 D3
16 D4
V+
SHDN
FB
1
2
3
4
5
6
7
8
9
24 DH
23 LX
22 BST
21 SKIP
20 D0
19 D1
18 D2
17 D3
16 OVP
FBS
FBS
MAX1711
MAX1710
CC
CC
ILIM
ILIM
V
CC
V
CC
TON
REF
TON
REF
GND 10
GNDS 11
PGOOD 12
15 V
DD
GND 10
GNDS 11
PGOOD 12
15 V
DD
14 PGND
13 DL
14 PGND
13 DL
QSOP
QSOP
26 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
