MAX1711 Maxim, MAX1711 Datasheet - Page 25

• Manufacturer Part Number: MAX1711
• Description: High-Speed / Digitally Adjusted Step-Down Controllers for Notebook CPUs
• Manufacturer: Maxim

Figure 11. Power-Stage PC Board Layout Example
• Keep the power traces and load connections short.
• LX and PGND connections to Q2 for current limiting
• When trade-offs in trace lengths must be made, it’s
This practice is essential for high efficiency. The use
of thick copper PC boards (2 oz. vs. 1 oz.) can en-
hance full-load efficiency by 1% or more. Correctly
routing PC board traces is a difficult task that must be
approached in terms of fractions of centimeters,
where a single milliohm of excess trace resistance
causes a measurable efficiency penalty.
must be made using Kelvin sense connections in
order to guarantee the current-limit accuracy. With
SO-8 MOSFETs, this is best done by routing power to
the MOSFETs from outside using the top copper
layer, while tying in PGND and LX inside (underneath)
the SO-8 package.
preferable to allow the inductor charging path to be
ALL ANALOG GROUNDS
CONNECT TO GND ONLY
NOTES: "STAR" GROUND IS USED.
SPLIT ANALOG GND PLANE AS SHOWN.
D1 IS DIRECTLY ACROSS Q2.
Step-Down Controllers for Notebook CPUs
BENEATH IC, 1 POINT ONLY.
GND
CONNECT GND TO PGND
V
CC
REF
I
LIM
CC
______________________________________________________________________________________
MAX1710
MAX1711
V
DD
VIA TO SOURCE
VIA TO LX
OF Q2
VIA TO PGND
NEAR Q2 SOURCE
Q1
High-Speed, Digitally Adjusted
INDUCTOR DISCHARGE PATH HAS LOW DC RESISTANCE
D1
Q2
L1
• Ensure that the FB connection to C
• Route high-speed switching nodes away from sensi-
• Make all pin-strap control input connections (SKIP,
made longer than the discharge path. For example,
it’s better to allow some extra distance between the
input capacitors and the high-side MOSFET than to
allow distance between the inductor and the low-side
MOSFET or between the inductor and the output filter
capacitor.
direct. However, in some cases it may be desirable to
deliberately introduce some trace length between the
FB inductor node and the output filter capacitor (see
the All-Ceramic-Capacitor Application section).
tive analog areas (CC, REF, ILIM).
ILIM, etc.) to GND or V
CIN
V
BATT
COUT
GND IN
VIA TO FB
NEAR COUT+
CC
rather than PGND or V
OUT
VIA TO GNDS
VIA TO FBS
is short and
GND
OUT
V
OUT
DD
.
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