MAX1632AEAI Datasheet, PDF (8/29 Pages) Maxim Integrated Products – Multi-Output, Low-Noise Power-Supply Controllers for Notebook Computers

Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
INPUT
C3
+5V OUTPUT
R1
C1
*
Q1
0.1μF
L1
Q2
5V ON/OFF
3.3V ON/OFF
10Ω
4.7μF
0.1μF
ON/OFF
0.1μF
V+ SHDN SECFB VL
SYNC
BST5
BST3
DH5
DH3
LX5
LX3
DL5 ^MAX1631A
MAX1634A _DL3
PGND
CSH5
CSL5
CSH3
CSL3
FB3
FB5
TIME/ON5
RUN/ON3
GND
REF
RESET
SKIP
STEER
SEQ
1μF
0.1μF
+5V ALWAYS ON
4.7μF
0.1μF
Q3
0.1μF
L2
Q4
R2
+3.3V OUTPUT
* ^C2
RESET OUTPUT
+2.5V ALWAYS ON
*1A SCHOTTKY DIODE REQUIRED
FOR THE MAX1631A (SEE OUTPUT
OVERVOLTAGE PROTECTION SECTION).
Figure 1. Standard 3.3V/5V Application Circuit (MAX1631A/MAX1634A)
_______Standard Application Circuit
The basic MAX1631A/MAX1634A dual-output 3.3V/5V
buck converter (Figure 1) is easily adapted to meet a
wide range of applications with inputs up to 28V by
substituting components from Table 1. These circuits
represent a good set of tradeoffs between cost, size,
and efficiency, while staying within the worst-case
specification limits for stress-related parameters, such
as capacitor ripple current. Do not change the frequen-
cy of these circuits without first recalculating compo-
nent values (particularly inductance value at maximum
battery voltage). Adding a Schottky rectifier across
each synchronous rectifier improves the efficiency of
these circuits by approximately 1%, but this rectifier is
otherwise not needed because the MOSFETs required
for these circuits typically incorporate a high-speed sili-
con diode from drain to source. Use a Schottky rectifier
rated at a DC current equal to at least 1/3 of the load
current.
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