Datasheet
MAX1973/MAX1974
V
OUT
= 2.5V
I
OUT(MAX)
= 1A
C
OUT
= 4.7µF
V
FB
= 1.25V
R
CS
= 0.26Ω
g
m
= 50µS
f
C
= 140kHz
Select the nearest standard value: C
C
= 560pF
Select the nearest standard value: R
C
= 43kΩ
PC Board Layout
A properly designed PC board layout is important in
any switching regulator. The switching power stage
requires particular attention. Follow these guidelines for
good PC board layout:
1) Place decoupling capacitors as close to IC pins as
possible. Keep the power ground plane (connected
to PGND) and signal ground plane (connected to
GND) separate. Connect the two ground planes with
a single connection from PGND to GND.
2) Input and output capacitors are connected to the
power ground plane; all other capacitors are con-
nected to the signal ground plane.
3) Keep the high-current paths as short and wide as
possible.
4) If possible, connect IN, LX, and PGND separately to
a large land area to help cool the IC to further
improve efficiency and long-term reliability.
5) Ensure all feedback connections are short and
direct. Place feedback resistors (if used) as close to
the IC as possible.
6) Route high-speed switching nodes (LX) away from
sensitive analog areas (FB, COMP, SS).
R
C
C
V
I
k
C
OUT
C
OUT
OUT MAX
=×
×
=
×
×
×
×
=
−
−
05
47 10
560 10
25
05 1
41 9
6
12
.
..
.
.
()
Ω
C
V
IR
g
f
pF
C
FB
OUT MAX CS
m
C
=
×
×××
×
=
×
××××
×
=
−
05
11
2
125
05 1
1
026
50 10
1
2 140000
547
6
.
.
..
()
π
π
Smallest 1A, 1.4MHz Step-Down Regulators
14 ______________________________________________________________________________________
Chip Information
TRANSISTOR COUNT: 1998
PROCESS: BiCMOS
V
OUT
(V) C
IN
(µF) C
OUT
(µF) C
C
(pF) R
C
(kΩ)
2.5 4.7 4.7 560 43
1.8 4.7 4.7 560 30
Table 4. Recommended Components for the MAX1973
V
OUT
(V) C
IN
(µF) C
OUT
(µF) C
C
(pF) R
C
(kΩ)
1.5 4.7 4.7 330 43
1.0 4.7 4.7 330 27
Table 5. Recommended Components for the MAX1974
Selector Guide
PART FEATURES
OUTPUT PRESET
MAX1973EUB
Voltage Margining
1.8V or 2.5V
MAX1974EUB
Power-OK Output
1V or 1.5V