MAX782 MAXIM [Maxim Integrated Products], MAX782 Datasheet - Page 9

• Manufacturer Part Number: MAX782
• Description: Triple-Output Power-Supply Controller for Notebook Computers
• Manufacturer: MAXIM [Maxim Integrated Products]

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.
Figure 1. MAX782 Application Circuit
150 F
+3.3V at 3A
C14
N1-N4 = Si9410DY
NOTE 1: BATTERY VOLTAGE RANGE 6.5V to 30V
NOTE 2: SEE FIGURE 5.
150 F
C7
BATTERY INPUT
WITH COMPONENTS SHOWN
SEE LOW-VOLTAGE (6-CELL) OPERATION SECTION.
CONTROL
INPUTS
+3.3V ON/OFF
5.5V TO 30V
25m
+5V ON/OFF
VPP
R1
OSC SYNC
(NOTE 1)
_______________________________________________________________________________________
1N5819
10 H
L1
D3
C1
33 F
(NOTE 2)
N1
Controller for Notebook Computers
0.01 F
N3
0.1 F
C9
C5
+3.3V Supply
1N4148
D1A
35
34
16
15
18
17
31
33
32
30
36
19
14
1
Triple-Output Power-Supply
GND
CS3
DA0
DA1
DB0
DB1
BST3
DH3
LX3
DL3
FB3
SS3
ON3
ON5
SYNC
V+
12
29
MAX782
REF PGND
13
C3
1 F
D1-D3
Q1-Q3
VPPA
VPPB
BST5
VL
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 V
5V, the +5V output gracefully falls with V
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.
VDD
DH5
CS5
DL5
SS5
LX5
FB5
VH
28
26
9
11
10
24
22
23
25
21
27
20
5
2, 3, 4
8, 7, 6
D1B
1N4148 C4
C8
0.01 F
0.1 F
C2
4.7 F
3
3
C11
1 F
C10
1 F
(NOTE 2)
N4
N2 1:2.2
1N5819
L2 10 H
EC11FS1
COMPARATOR SUPPLY INPUT
COMPARATOR INPUTS
COMPARATOR OUTPUTS
D4
0V, 5V, 12V
0V, 5V, 12V
+5V at 5mA
D2
3.3V AT 5mA
C12
2.2 F
+15V AT 300mA, SEE
HIGH-SIDE SUPPLY (VDD)
SECTION.
20m
R2
+5V Supply
IN
IN
approaches
+5V at 3A
until the VL
C6
330 F
C13
33 F
9