MAX782 Просмотр технического описания (PDF) - Maxim Integrated
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MAX782 Datasheet PDF : 32 Pages
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Triple-Output Power-Supply
Controller for Notebook Computers
BATTERY INPUT
C1
5.5V TO 30V
(NOTE 1)
33µF
VPP
CONTROL
INPUTS
+3.3V at 3A
R1
25mΩ
C14 C7
150µF 150µF
L1
10µH
D3
1N5819
+3.3V ON/OFF
+5V ON/OFF
OSC SYNC
D1A
1N4148
C5
0.1µF
N1
N3
(NOTE 2)
C9
0.01µF
N1- N4 = Si9410DY
NOTE 1: BATTERY VOLTAGE RANGE 6.5V to 30V
WITH COMPONENTS SHOWN
SEE LOW-VOLTAGE (6-CELL) OPERATION SECTION.
NOTE 2: SEE FIGURE 5.
29
V+
16
DA0
15
DA1
18
DB0
17
DB1
28
VL
9
VPPA
11
VPPB
10
VDD
MAX782
C2
4.7µF
C11
1µF
C10
1µF
D1B
1N4148 C4
C13
33µF
+5V at 5mA
0V, 5V, 12V
0V, 5V, 12V
+15V AT 300mA, SEE
D2
EC11FS1
HIGH-SIDE SUPPLY (VDD)
SECTION.
31
BST3
33 DH3
24
BST5
22
DH5
0.1µF
N2 1:2.2
C12
2.2µF
32
LX3
30 DL3
35
CS3
23
LX5
25
DL5
21
CS5
+5V at 3A
L2 10µH
R2
N4
D4
1N5819
20mΩ
C6
330µF
34 FB3
36 SS3
1 ON3
FB5 27
SS5 20
5
VH
(NOTE 2)
C8
0.01µF
COMPARATOR SUPPLY INPUT
19 ON5
2, 3, 4
D1-D3
3
COMPARATOR INPUTS
14 SYNC
8, 7, 6
Q1-Q3
3
COMPARATOR OUTPUTS
GND REF PGND
12 13 26
C3
1µF
3.3V AT 5mA
Figure 1. MAX782 Application Circuit
+3.3V Supply
The +3.3V supply is produced by a current-mode PWM
step-down regulator using two small N-channel MOSFETs,
a catch diode, an inductor, and a filter capacitor.
Efficiency is greatly enhanced by the use of the second
MOSFET (connected from LX3 to PGND), which acts as
a synchronous rectifier. A 100nF capacitor connected
to BST3 provides the drive voltage for the high-side
(upper) N-channel MOSFET.
A current limit set by an external sense resistor prevents
excessive inductor current during start-up or under
short-circuit conditions. A soft-start capacitor can be
chosen to tailor the rate at which the output ramps up.
This supply can be turned on by connecting ON3 to
logic high, or can be turned off by connecting ON3 to
GND. All logic levels are TTL and CMOS compatible.
+5V Supply
The +5V output is produced by a current-mode PWM
step-down regulator similar to the +3.3V supply. This
supply uses a transformer primary as its inductor, the
secondary of which is used for the high-side (VDD)
supply. It also has current limiting and soft-start. It can
be turned off by connecting ON5 to GND, or turned on
by connecting ON5 to logic high.
The +5V supply’s dropout voltage, as configured in
Figure 1, is typically 400mV at 2A. As VIN approaches
5V, the +5V output gracefully falls with VIN until the VL
regulator output hits its undervoltage lockout threshold.
At this point, the +5V supply turns off.
The default frequency for both PWM controllers is
300kHz (with SYNC connected to REF), but 200kHz
may be used by connecting SYNC to GND or VL.
_______________________________________________________________________________________ 9
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