MAX1630_05 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
ON/OFF
10Ω
4.7μF
0.1μF
0.1μF
V+ SHDN SECFB VL
SYNC
BST5
BST3
DH5
DH3
LX5
LX3
DL5 ^MAX1631
MAX1634 _DL3
PGND
CSH5
CSL5
CSH3
CSL3
FB3
FB5
TIME/ON5
RUN/ON3
GND
REF
RESET
SKIP
STEER
SEQ
1μF
Figure 1. Standard 3.3V/5V Application Circuit (MAX1631/MAX1634)
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 MAX1631 (SEE OUTPUT
OVERVOLTAGE PROTECTION SECTION).
_______Standard Application Circuit
The basic MAX1631/MAX1634 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. Don’t change the frequency
of these circuits without first recalculating component
values (particularly inductance value at maximum bat-
tery voltage). Adding a Schottky rectifier across each
synchronous rectifier improves the efficiency of these
circuits by approximately 1%, but this rectifier is other-
wise not needed because the MOSFETs required for
these circuits typically incorporate a high-speed silicon
diode from drain to source. Use a Schottky rectifier
rated at a DC current equal to at least one-third of the
load current.
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