Du a l-Ou t p u t P o w e r-S u p p ly
Co n t ro lle r fo r No t e b o o k Co m p u t e rs
MAX786
Table 1. Surface-Mount Components
(See Figure 1 for Standard Application Circuit.)
COMPONENT
SPECIFICATION
MANUFACTURER
PART NO.
TPSE226M035R0100
595D336X0035R
AVX
Sprague
C1, C10
33µF, 35V tantalum capacitors
AVX
Sprague
TAJB475M016
595D475X0016A
C2
C3
4.7µF, 6V tantalum capacitor
1µF, 20V tantalum capacitor
AVX
Sprague
TAJA105M025
595D105X0020A2B
C4, C5
C6
0.1µF, 16V ceramic capacitors
330µF, 10V tantalum capacitor
150µF, 10V tantalum capacitors
0.01µF, 16V ceramic capacitors
1N4148-type dual diodes
1N5819 SMT diodes
Murata-Erie
Sprague
GRM42-6X7R104K50V
595D337X0010R
595D157X0010D
GRM42-6X7R103K50V
CMPD2836
C7, C12
C8, C9
D2A, D2B
D1, D3
L1, L2
Sprague
Murata-Erie
Central Semiconductor
Nihon
EC10QS04
10µH, 2.65A inductors
Sumida
CDR125-100
N1–N4
R1, R2
N-channel MOSFETs (SO-8)
0.025Ω, 1% (SMT) resistors
Siliconix
Si9410DY
IRC
LR2010-01-R025-F
current. The main switching outputs track the reference
voltage. Loading the reference will reduce the main
outputs slightly, according to the reference load-regula-
tion error.
Table 2. Component Suppliers
FACTORY FAX
COMPANY
USA PHONE
[COUNTRY CODE]
(803) 946-0690
(800) 282-4975
Both the VL and REF outputs remain active, even when
the switching regulators are turned off, to supply mem-
ory keep-alive power (see Shutdown Mode section).
AVX
[1] (803) 626-3123
Central Semiconductor [1] (516) 435-1824 (516) 435-1110
IRC
[1] (512) 992-3377 (512) 992-7900
[1] (814) 238-0490 (814) 237-1431
These linear-regulator outputs can be directly connected
to the corresponding step-down regulator outputs (i.e.,
REF to +3.3V, VL to +5V) to keep the main supplies alive
in standby mode. However, to ensure start-up, standby
load currents must not exceed 5mA on each supply.
Murata-Erie
Nihon
[81] 3-3494-7414
(805) 867-2555
Siliconix
Sprague
Sumida
[1] (408) 970-3950 (408) 988-8000
[1] (603) 224-1430 (603) 224-1961
Fault Protection
The +3.3V and +5V PWM supplies and the compara-
tors are disabled when either of two faults is present:
VL < +4.0V or REF < +2.8V (85% of its nominal value).
[81] 3-3607-5144
(847) 956-0666
__________________De s ig n P ro c e d u re
In t e rn a l VL a n d REF S u p p lie s
An internal linear regulator produces the 5V used by the
internal control circuits. This regulator’s output is avail-
able on pin VL and can source 5mA for external loads.
Bypass VL to GND with 4.7µF. To save power, when the
+5V switch-mode supply is above 4.5V, the internal lin-
ear regulator is turned off and the high-efficiency +5V
switch-mode supply output is connected to VL.
Figure 1’s schematic and Table 2’s component list
show values suitable for a 3A, +5V supply and a 3A,
+3.3V supply. This circuit operates with input voltages
from 6.5V to 30V, and maintains high efficiency with
output currents between 5mA and 3A (see the Typical
Operating Characteristics). This circuit’s components
may be changed if the design guidelines described in
this s e c tion a re us e d — b ut b e fore b e g inning the
d e s ig n, the following informa tion s hould b e firmly
established:
The internal 3.3V bandgap reference (REF) is powered
by the internal 5V VL supply. It can furnish up to 5mA.
Bypass REF to GND with 0.22µF, plus 1µF/mA of load
______________________________________________________________________________________ 13
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
