MAX786R View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX786R Datasheet PDF : 20 Pages
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Dual-Output Power-Supply
Controller for Notebook Computers
_________________Detailed Description
The MAX786 converts a 5.5V to 30V input to four outputs
(Figure 1). It produces two high-power, PWM, switch-
mode supplies, one at +5V and the other at +3.3V. The
two supplies operate at either 300kHz or 200kHz,
allowing for small external components. Output current
capability depends on external components, and can
exceed 6A on each supply. An internal 5V, 5mA supply
(VL) and a 3.3V, 5mA reference voltage are also gener-
ated via linear regulators, as shown in Figure 2. Fault
protection circuitry shuts off the PWMs when the inter-
nal supplies lose regulation.
Two precision voltage comparators are also included.
Their output stages permit them to be used as level
translators for driving external N-channel MOSFETs in
load-switching applications, or for more conventional
logic signals.
The MAX786 has two close relatives: the MAX782 and
the MAX783. The MAX782 and MAX783 each include
an extra flyback winding regulator and linear regulators
for dual, +12V/programmable PCMCIA VPP outputs.
The MAX782/MAX783 data sheet contains extra appli-
cations information on the MAX786 not found in this
data sheet.
+3.3V Switch-Mode Supply
The +3.3V supply is generated by a current-mode,
PWM step-down regulator using two N-channel
MOSFETs, a rectifier, and an LC output filter (Figure 1).
The gate-drive signal to the high-side MOSFET, which
must exceed the battery voltage, is provided by
a boost circuit that uses a 100nF capacitor connected
to BST3.
INPUT
5.5V TO 30V
(NOTE 1) C1
33µF
+3.3V
AT
3A
R1
25mΩ
L1 N1
10µH
C7 C12
150µF 150µF
D1
1N5819
N3
D2A
1N4148
C5
0.1µF
+3.3V ON/OFF
+5V ON/OFF
SHUTDOWN
OSC SYNC
(NOTE 2)
C9
0.01µF
NOTE 1: INPUT VOLTAGE RANGE 6.5V TO 30V
AS SHOWN. SEE LOW-VOLTAGE
(6-CELL) OPERATION SECTION FOR
DETAILS.
NOTE 2: USE SHORT, KELVIN-CONNECTED PC
BOARD TRACES PLACED VERY CLOSE
TO ONE ANOTHER.
23
22
V+
VL
25
BST3
27
DH3
26
LX3
18
BST5
16
DH5
17
LX5
24 DL3
DL5 19
MAX786
1 CS3
CS5 15
28 FB3
FB5 21
2
SS3
14
SS5
3
ON3
6
VH
13
ON5
4
D1
12
SHDN
8
Q1
11
SYNC
5
D2
7
Q2
GND REF PGND
9 10 20
C3
1µF
D2B
1N4148C4
0.1µF
N2 L2
10µH
D3
N4
1N5819
C10
33µF
+5V AT 5mA
4.7µF
+5V
R2
AT
25m
3A
C6
330µF
(NOTE 2)
C8
0.01µF
COMPARATOR SUPPLY INPUT
IN
COMPARATOR 1
OUT
IN COMPARATOR 2
OUT
+3.3V AT 5mA
Figure 1. MAX786 Application Circuit
8 _______________________________________________________________________________________
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