MAX782CBX Maxim Integrated Products, MAX782CBX Datasheet - Page 24

• Manufacturer Part Number: MAX782CBX
• Description: DC/DC Switching Controllers
• Manufacturer: Maxim Integrated Products

Specifications of MAX782CBX

• Number Of Outputs: 2
• Output Voltage: 3.3 V
• Output Current: 18 A
• Input Voltage: 5.5 V to 30 V
• Mounting Style: SMD/SMT
• Package / Case: SSOP-36
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Case: SSOP36
• Dc: 97+

Triple-Output Power-Supply
Controller for Notebook Computers
When the +5V and +3.3V supplies are off, the complete
MAX782 circuit consumes only about 70µA, plus any
leakage through the off MOSFETs. Some NiCd batter-
ies can be damaged if they are fully discharged and
then left for long periods (months) under load. Even
100µA can do damage if left long enough.
The complete power-supply system can be shut down
by taking ON5 low, cutting the supply to the MAX782’s
V+ pin, while the bootstrapped +5V supply is turned
off. This removes the supply from the controller, and
turns off all the supplies. In this condition, the current
consumption drops to the level of the leakage currents
in the off transistors. Switching the V+ supply off is
easy because the V+ line draws very little power;
switching the entire power input from the battery would
be more difficult.
Figure 12 shows a logic interface for a momentary
switch that toggles the whole system on and off. The
logic circuit runs from the battery supply, so the input
voltage from the battery is limited to the normal operat-
ing range for the flip-flop gates, which is usually 18V for
4000-series CMOS circuits. The active-high OFF input
permits the supplies to be turned off under logic control
as well as when the switch is pushed. If this logic input
is not required, omit R1 and Q1. The supplies can only
be turned on using the hardware switch. For automatic
turn-off, connect the OFF input to a battery-voltage
sensing comparator or to a timer powered from VL.
Ensure that any signal connected to OFF does not
glitch high at power-up.
Figure 13 shows a low-dropout linear regulator
designed to provide an additional VPP output from the
VDD line. It can be turned off with a logic-level signal;
its output can be switched to 5V or 12V; and it pro-
vides excellent rejection of the high-frequency noise
on VDD. If a monolithic linear regulator is used,
choose one having good PSRR performance at
300kHz.
24
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Generating Additional VPP Outputs
Using External Linear Regulators
Total Shutdown Circuits
Figure 12. Hardware/Software Total Shutdown Circuit
Figure 13. External Regulator For Additional VPP Outputs
VDD
OFF/ON
FROM MAX782
FROM MAX782
REF
V
ON/
OFF
BATT
1M
(+5.5V TO +18V)
R5
100k
100nF
1 F
C1
X = DON'T CARE
OFF/ON
OFF
Q2
2N7002
1 F
0
1
0
C4
10nF
3
2
1N4148
1N4148
CD4011B
1M
1M
1M
1M
R1
OP27
U1
7
4
12/5
S
X
0
1
R
Q1
2N4401
R4
1k
12/5
2N4403
6
Q1
1N4148
1N4148
10nF
ON
C3
ON5
V
ON
OUT
1M
12
0
5
Q3
2N7002
16.9k
(V)
R1
VL
ON5
MAX782
6.8 F
R3
26.7k
R2
6.34k
PGND
V+
C2
ZETEX
ZVP2106G
SOT 223
OUT