Rainbow Electronics MAX782 User Manual

19-0146; Rev 2; 5/94

Evaluation Kit

Information Included

Controller for Notebook Computers

_______________General Description

The MAX782 is a system-engineered power-supply con­troller for notebook computers or similar battery-powered
equipment. It provides two high-performance step-down
(buck) pulse-width modulators (PWMs) for +3.3V and +5V,
and dual PCMCIA VPP outputs powered by an integral fly­back winding controller. Other functions include dual, low­dropout, micropower linear regulators for CMOS/RTC back­up, and three precision low-battery-detection comparators.

High efficiency (95% at 2A; greater than 80% at loads
from 5mA to 3A) is achieved through synchronous recti­fication and PWM operation at heavy loads, and Idle­ModeTMoperation at light loads. It uses physically
small components, thanks to high operating frequen­cies (300kHz/200kHz) and a new current-mode PWM
architecture that allows for output filter capacitors as
small as 30µF per ampere of load. Line- and load-tran­sient response are terrific, with a high 60kHz unity-gain
crossover frequency allowing output transients to be
corrected within four or five clock cycles. Low system
cost is achieved through a high level of integration and
the use of low-cost, external N-channel MOSFETs. The
integral flyback winding controller provides a low-cost,
+15V high-side output that regulates even in the
absence of a load on the main output.

Triple-Output Power-Supply

___________________________Features

♦ Dual PWM Buck Controllers (+3.3V and +5V)
♦ Dual PCMCIA VPP Outputs (0V/5V/12V)
♦ Three Precision Comparators or Level Translators
♦ 95% Efficiency
♦ 420µA Quiescent Current;

70µA in Standby (linear regulators alive)

♦ 5.5V to 30V Input Range
♦ Small SSOP Package
♦ Fixed Output Voltages Available:

3.3 (standard)

3.45 (High-Speed Pentium™)

3.6 (PowerPC™)

______________Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX782CBX 0°C to +70°C 36 SSOP
MAX782RCBX 0°C to +70°C 36 SSOP
MAX782SCBX 0°C to +70°C 36 SSOP

Ordering Information continued on last page.

__________________Pin Configuration

TOP VIEW

Other features include low-noise, fixed-frequency PWM
operation at moderate to heavy loads and a synchroniz­able oscillator for noise-sensitive applications such as
electromagnetic pen-based systems and communicat­ing computers. The MAX782 is a monolithic BiCMOS IC
available in fine-pitch, SSOP surface-mount packages.

_______________________Applications

Notebook Computers
Portable Data Terminals
Communicating Computers
Pen-Entry Systems

______Typical Application Diagram

+3.3V

+5V

µP
MEMORY
PERIPHERALS

DUAL

PCMCIA

SLOTS

5.5V
TO

30V

VPP

CONTROL

ON3
ON5

SYNC

Idle-Mode is a trademark of Maxim Integrated Products. Pentium is a trademark of Intel

™

MAX782

4



POWER

SECTION

SUSPEND POWER

LOW-BATTERY WARNING

VPP (0V/5V/12V)
VPP (0V/5V/12V)

ON3

1

D1

2

D2

3

D3

4

VH

5

Q3
Q2

Q1

VPPA

VDD

VPPB

GND

REF

SYNC

DA1
DA0
DB1

DB0

MAX782

6
7
8

9
10
11
12
13
14
15
16
17
18

SSOP

.

PowerPC is a trademark of IBM.

MAX782

V

OUT

3.3V

3.45V

3.6V

36

SS3
CS3

35

FB3

34

DH3

33

LX3

32
31

BST3

30

DL3

29

V+

28

VL

27

FB5

26

PGND

25

DL5

24

BST5

23

LX5

22

DH5

21

CS5

20

SS5

19

ON5

________________________________________________________________

Maxim Integrated Products

Call toll free 1-800-998-8800 for free samples or literature.

1

Triple-Output Power-Supply
Controller for Notebook Computers

ABSOLUTE MAXIMUM RATINGS

V+ to GND.................................................................-0.3V, +36V

PGND to GND........................................................................±2V

VL to GND ...................................................................-0.3V, +7V

BST3, BST5 to GND ..................................................-0.3V, +36V

LX3 to BST3.................................................................-7V, +0.3V

LX5 to BST5.................................................................-7V, +0.3V

Inputs/Outputs to GND

MAX782

(D1-D3, ON5, REF, SYNC, DA1, DA0, DB1, DB0, ON5,

SS5, CS5, FB5, CS3, FB3, SS3, ON3)..........-0.3V, (VL + 0.3V)

VDD to GND.................................................................-0.3V, 20V

VPPA, VPPB to GND.....................................-0.3V, (VDD + 0.3V)

VH to GND...................................................................-0.3V, 20V

Q1-Q3 to GND.................................................-0.3V, (VH + 0.3V)

DL3, DL5 to PGND...........................................-0.3V, (VL + 0.3V)

Stresses beyond those listed under “Absolute Maximum Ratings‘” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(V+ = 15V, GND = PGND = 0V, IVL= I
unless otherwise noted.)

PARAMETER CONDITIONS MIN TYP MAX UNITS

+3.3V AND 5V STEP-DOWN CONTROLLERS

Input Supply Range 5.5 30 V

FB5 Output Voltage 4.80 5.08 5.20 V

FB3 Output Voltage

Load Regulation Either controller (CS_ - FB_ = 0mV to 70mV) 2 %
Line Regulation Either controller (V+ = 6V to 30V) 0.03 %/V

Current-Limit Voltage
SS3/SS5 Source Current 2.5 4.0 6.5 µA

SS3/SS5 Fault Sink Current 2 mA

15V FLYBACK CONTROLLER

VDD Regulation Setpoint Falling edge, hysteresis = 1% V
VDD Shunt Setpoint Rising edge, hysteresis = 1% V
VDD Shunt Current VDD = 20V 23 mA

Quiescent VDD Current 140 300 µA

VDD Off Current 15 30 µA

PCMCIA REGULATORS (Note 1)

VPPA/VPPB Output Voltage

VPPA/VPPB Off Input Current Program to Hi-Z, VDD = 19V, 0V < VPP < 12V 35 µA

= 0mA, ON3 = ON5 = 5V, other digital input levels are 0V or +5V, TA = T

REF

0mV < (CS5-FB5) < 70mV, 6V < V+ < 30V
(includes load and line regulation)

0mV < (CS3-FB3) < 70mV, 6V < V+ < 30V
(includes load and line regulation)

CS3-FB3 or CS5-FB5
CS5-FB5 (VDD < 13V, flyback mode) -50 -100 -160

VDD = 18V, ON3 = ON5 = 5V,
VPPA/B programmed to 12V with no external load

VDD = 18V, ON3 = ON5 = 5V,
VPPA/B programmed to Hi-Z or 0V

Program to 12V, 13V < VDD < 19V, 0mA < IL< 60mA 11.6 12.1 12.5
Program to 5V, 13V < VDD < 19V, 0mA < IL< 60mA 4.85 5.05 5.20
Program to 0V, 13V < VDD < 19V, -0.3mA < IL< 0.3mA -0.3 0.3

DH3 to LX3..................................................-0.3V, (BST3 + 0.3V)

DH5 to LX5..................................................-0.3V, (BST5 + 0.3V)

REF, VL, VPP Short to GND........................................Momentary

REF Current.........................................................................20mA

VL Current...........................................................................50mA

VPPA, VPPB Current.........................................................100mA

Continuous Power Dissipation (T

SSOP (derate 11.76mW/°C above +70°C) ...................941mW

Operating Temperature Ranges:

MAX782CBX/MAX782__CBX...............................0°C to +70°C

MAX782EBX/MAX782__EBX ............................-40°C to +85°C

Storage Temperature Range.............................-65°C to +160°C

Lead Temperature (soldering, 10sec).............................+300°C

MAX782
MAX782R
MAX782S

= +70°C)

A

3.17 3.35 3.46

3.32 3.50 3.60

3.46 3.65 3.75

80 100 120

13 14
18 20

MIN

to T

mV

V
V
V

V

MAX

,

2 _______________________________________________________________________________________

Triple-Output Power-Supply

Controller for Notebook Computers

ELECTRICAL CHARACTERISTICS (continued)

(V+ = 15V, GND = PGND = 0V, IVL= I
unless otherwise noted.)

PARAMETER CONDITIONS MIN TYP MAX UNITS

INTERNAL REGULATOR AND REFERENCE

VL Output Voltage
VL Fault Lockout Voltage
VL/FB5 Switchover Voltage Rising edge of FB5, hysteresis = 1% 4.2 4.7 V

REF Output Voltage No external load (Note 2) 3.24 3.36 V

REF Fault Lockout Voltage Falling edge 2.4 3.2

REF Load Regulation 0mA < IL< 5mA 30 75 mV

V+ Standby Current 70 110 µA

Quiescent Power Consumption

(both PWM controllers on)

V+ Off Current

COMPARATORS

D1-D3 Trip Voltage Falling edge, hysteresis = 1%

D1-D3 Input Current D1 = D2 = D3 = 0V to 5V

Q1-Q3 Source Current VH = 15V, Q1-Q3 forced to 2.5V 12 20 30 µA

Q1-Q3 Sink Current

Q1-Q3 Output High Voltage

Q1-Q3 Output Low Voltage

Quiescent VH Current VH = 18V, D1 = D2 = D3 = 5V, no external load

OSCILLATOR AND INPUTS/OUTPUTS

Oscillator Frequency

SYNC High Pulse Width 200 ns

SYNC Low Pulse Width 200 ns

SYNC Rise/Fall Time Not tested 200 ns

Oscillator SYNC Range 240 350 kHz

Maximum Duty Cycle

Input Low Voltage ON3, ON5, DA0, DA1, DB0, DB1, SYNC 0.8 V

Input High Voltage

Input Current

DL3/DL5 Sink/Source Current DL3, DL5 forced to 2V 1 A

DH3/DH5 Sink/Source Current BST3-LX3 = BST5-LX5 = 4.5V, DH3, DH5 forced to 2V 1 A

DL3/DL5 On Resistance High or low 7 Ω

DH3/DH5 On Resistance High or low, BST3-LX3 = BST5-LX5 = 4.5V 7 Ω

Note 1: Output current is further limited by maximum allowable package power dissipation.
Note 2: Since the reference uses VL as its supply, V+ line regulation error is insignificant.

= 0mA, ON3 = ON5 = 5V, other digital input levels are 0V or +5V, TA = T

REF

ON5 = ON3 = 0V, 5.5V < V+ < 30V, 0mA < IL< 25mA
Falling edge, hysteresis = 1% 3.6 4.2 V

D1 = D2 = D3 = ON3 = ON5 = DA0 = DA1 = DB0 =
DB1 = 0V, V+ = 30V

D1 = D2 = D3 = DA0 = DA1 = DB0 = DB1 = 0V,
FB5 = CS5 = 5.25V, FB3 = CS3 = 3.5V

FB5 = CS5 = 5.25V, VL switched over to FB5 30 60 µA

VH = 15V, Q1-Q3 forced to 2.5V 200 500 1000 µA
I

= 5µA, VH = 3V

SOURCE

I

= 20µA, VH = 3V

SINK

SYNC = 3.3V 270 300 330
SYNC = 0V or 5V 170 200 230

SYNC = 3.3V 89 92
SYNC = 0V or 5V 92 95

ON3, ON5, DA0, DA1, DB0, DB1 2.4
SYNC VL-0.5
ON3, ON5, DA0, DA1, DB0, DB1, VIN= 0V or 5V

4.5 5.5

6.0 8.6

1.61 1.69 V

VH-0.5 V

610µA

MIN

±100

0.4 V

±1 µA

to T

V

V

mW

nA

kHz

%

V

MAX782

,

MAX

_______________________________________________________________________________________ 3

Triple-Output Power-Supply
Controller for Notebook Computers

__________________________________________Typical Operating Characteristics

(Circuit of Figure 1, Transpower transformer type TTI5870, TA= +25°C, unless otherwise noted.)

+5V OUTPUT CURRENT, 200kHz

100

MAX782

90

EFFICIENCY (%)

80

70

0.001 0.1 10

0.01 1

+5V OUTPUT CURRENT (A)

+3.3V OUTPUT CURRENT, 200kHz

100

+5V ON, +5V LOAD = 0mA
IDD = 0mA, 
COMPONENTS OF TABLE 5

90

EFFICIENCY (%)

80

70

0.001 0.1 10

0.01 1

+3.3V OUTPUT CURRENT (A)

+5V OUTPUT CURRENT vs.

MINIMUM INPUT VOLTAGE, 300kHz

9

8

EFFICIENCY vs.

VIN = 10V

VIN = 15V

COMPONENTS,
OF TABLE 5. SYNC = 0V,
+3.3V OFF, I

EFFICIENCY vs.

VIN = 6V

VIN = 15V

VIN = 6V

DD

VIN = 10V

IDD = 300mA

= 0mA

EFFICIENCY vs.

+5V OUTPUT CURRENT, 300kHz

100

IDD = 0mA
+3.3V OFF

VIN = 15V

90

EFFICIENCY (%)

80

70

0.001 0.01 1
+5V OUTPUT CURRENT (A)

EFFICIENCY vs.

+3.3V OUTPUT CURRENT, 300kHz

100

I

= 0mA

DD

+5V ON
+5V LOAD = 0mA

90

EFFICIENCY (%)

80

70

0.001 0.01 1

+3.3V OUTPUT CURRENT (A)

+5V OUTPUT CURRENT vs.

MINIMUM INPUT VOLTAGE, 200kHz

9

COMPONENTS OF TABLE 4,
SYNC = 0V

8

VIN = 6V

VIN = 30V

0.1 10

VIN = 6V

VIN = 15V

VIN = 30V

0.1 10

IDD = 300mA

IDD OUTPUT CURRENT vs. INPUT VOLTAGE
COILTRONIX CTX03-12062 TRANSFORMER

10

+3V LOAD = 0mA R

1

0.1

LOAD CURRENT (A)

DD

I

0.01
510 20 30

10000

1000

100

INPUT CURRENT (µA)

10

0 5 15 25

1000

100

+5V LOAD = 0A-1A

15 25

INPUT VOLTAGE (V)

QUIESCENT INPUT CURRENT vs.

INPUT VOLTAGE

+3.3V LOAD = +5V LOAD = 0mA

+5V, +3V ON

10 20 30

INPUT VOLTAGE (V)

SWITCHING FREQUENCY vs.

LOAD CURRENT

CIRCUIT OF FIGURE 1,
SYNC = REF (300kHz)
ON3 = ON5 = 5V

+5V, VIN = 7.5V

= 0.020Ω

SENSE

+5V LOAD = 3A

+5V, +3V OFF

7

6

MINIMUM INPUT VOLTAGE (V)

5

0.01 0.1 10
+5V OUTPUT CURRENT (A)

IDD = 140mA

IDD = 60mA

IDD = 0mA

1

7

6

MINIMUM INPUT VOLTAGE (V)

5

0.01 0.1 10
+5V LOAD CURRENT (A)

IDD = 140mA

I

= 60mA

DD

IDD = 0mA

1

10

+5V, VIN = 30V

1

SWITCHING FREQUENCY (kHz)

0.1
100µA 10mA 1A

1mA 100mA

LOAD CURRENT

4 _______________________________________________________________________________________

+3.3V, VIN = 7.5V

Triple-Output Power-Supply

Controller for Notebook Computers

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, Transpower transformer type TTI5870, TA= +25°C, unless otherwise noted.)

PULSE-WIDTH MODULATION MODE WAVEFORMS

HORIZONTAL = 500ns/div
+5V OUTPUT CURRENT = 1A
INPUT VOLTAGE = 16V

+5V LOAD-TRANSIENT RESPONSE

LX VOLTAGE
10V/div

+5V OUTPUT
VOLTAGE
50mV/div

3A

LOAD CURRENT

0A

HORIZONTAL = 5µs/div
+5V OUTPUT CURRENT = 42mA
INPUT VOLTAGE = 16V

IDLE-MODE WAVEFORMS

+3.3V LOAD-TRANSIENT RESPONSE

LX VOLTAGE
10V/div

+5V OUTPUT
VOLTAGE
50mV/div

3A

LOAD CURRENT

0A

MAX782

HORIZONTAL = 200µs/div

= 15V

V

IN

_______________________________________________________________________________________ 5

+5V OUTPUT
50mV/div

HORIZONTAL = 200µs/div
V

= 15V

IN

+3.3V OUTPUT
50mV/div

Triple-Output Power-Supply
Controller for Notebook Computers

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, Transpower transformer type TTI5870, VDD ≥ 13V, TA= +25°C, unless otherwise noted.)

+5V LINE-TRANSIENT RESPONSE, RISING

MAX782

HORIZONTAL = 20µs/div
I

= 2A

LOAD

+3.3V LINE-TRANSIENT RESPONSE, RISING

+5V OUTPUT
50mV/div

VIN, 10V TO 16V
2V/div

+3.3V OUTPUT
50mV/div

, 10V TO 16V

V

IN

2V/div

+5V LINE-TRANSIENT RESPONSE, FALLING

HORIZONTAL = 20µs/div
I

= 2A

LOAD

+3.3V LINE-TRANSIENT RESPONSE, FALLING

+5V OUTPUT
50mV/div

VIN, 16V TO 10V
2V/div

+3.3V OUTPUT
50mV/div

, 16V TO 10V

V

IN

2V/div

HORIZONTAL = 20µs/div
I

= 2A

LOAD

HORIZONTAL = 20µs/div
I

= 2A

LOAD

6 _______________________________________________________________________________________

Triple-Output Power-Supply

Controller for Notebook Computers

______________________________________________________________Pin Description

PIN

10

NAME FUNCTION

1

2

3

4

5

6

7

8

9

ON3 Logic input to turn on +3.3V. Logic high turns on the regulator. Connect to VL for automatic start-up.

D1

D2

D3

VH

Q3

Q2

Q1

VPPA 0V, 5V, 12V, Hi-Z PCMCIA VPP output. Sources up to 60mA. Controlled by DA0 and DA1.

VDD

VPPB 0V, 5V, 12V, Hi-Z PCMCIA VPP output. Sources up to 60mA. Controlled by DB0 and DB1.11

#1 level-translator/comparator noninverting input. Inverting comparator input is internally connected to

1.650V. Controls Q1. Connect to GND if unused.
#2 level-translator/comparator noninverting input. Inverting comparator input is internally connected to

1.650V. Controls Q2. Connect to GND if unused.
#3 level-translator/comparator noninverting input. Inverting comparator input is internally connected to

1.650V. Controls Q3. Connect to GND if unused.
External supply input for level-translator/comparator. For N-channel FET drive, connect to VDD or external

+13V to +18V supply. For low-battery comparators, connect to +3.3V or +5V (or to VL/REF).
#3 level-translator/comparator output. Sources 20µA from VH when D3 is high. Sinks 500µA to GND

when D3 is low, even with VH = 0V.
#2 level-translator/comparator output. Sources 20µA from VH when D2 is high. Sinks 500µA to GND

when D2 is low, even with VH = 0V.
#1 level-translator/comparator output. Sources 20µA from VH when D1 is high. Sinks 500µA to GND

when D1 is low, even with VH = 0V.

15V flyback input (feedback). A weak shunt regulator conducts 3mA to GND when VDD exceeds 19V.
Also the supply input to the VPP regulators.

MAX782

GND Low-current analog ground12

REF13

SYNC14

DA1, DA0,

DB1, DB0

SS520

21

23 LX5 +5V-supply inductor connection

CS5

DH5 +5V-supply external MOSFET high-side switch-drive output22

3.3V reference output. Sources up to 5mA for external loads. Bypass to GND with 1µF/mA load or

0.22µF minimum.
Oscillator frequency control and synchronization input: Connect to VL or to GND for f = 200kHz; connect

to REF for f = 300kHz. For external synchronization in the 240kHz to 350kHz range, a high-to-low transi­tion causes the start of a new cycle.

Intel 82365 compatible PCMCIA VPP control inputs (see Table 1)15-18

Logic input to turn on +5V. Logic high turns on the regulator. Connect to VL for automatic startup.19 ON5

+5V-supply soft-start control input. Ramp time to full current limit is 1ms/nF of capacitance to GND.
+5V-supply current-sense input. +100mV = current limit in buck mode, -100mV = current limit in flyback

mode (where the ±100mV are referenced to FB5).

_______________________________________________________________________________________ 7

Triple-Output Power-Supply
Controller for Notebook Computers

_________________________________________________Pin Description (continued)

PIN NAME FUNCTION

24

25

MAX782

26

27

28

29

30

31

32

33

34

BST5 +5V-supply boost capacitor connection (0.1µF to LX5)

DL5 +5V-supply external MOSFET synchronous-rectifier drive output

PGND Power ground

FB5 +5V-supply feedback input and low-side current-sense terminal

Internal 5V-supply output. Bypass with 4.7µF. This pin is linearly regulated from V+ or switched to the

VL

+5V output to improve efficiency. VL is always on and can source up to 5mA for external loads.

V+ Main (battery) input: 5.5V to 30V

DL3 +3.3V-supply external MOSFET synchronous-rectifier drive output

BST3 +3.3V-supply boost capacitor connection (0.1µF to LX3)

LX3 +3.3V-supply inductor connection

DH3

FB3

CS3 +3.3V-supply current-sense input. Maximum is +100mV referenced to FB3.35

SS3 +3.3V-supply soft-start control input. Ramp time to full current limit is 1ms/nF of capacitance to GND.36

+3.3V-supply external MOSFET high-side switch-drive output

+3.3V-supply feedback and low-side current-sense terminal

Table 1. Truth Table for VPP Control Pins

D_0 D_1 VPP_

0
0
1
1

0
1
0
1

0V

5V
12V
Hi-Z

_______________Detailed Description

The MAX782 converts a 5.5V to 30V input to five outputs
(Figure 1). It produces two high-power, switch-mode,
pulse-width modulated (PWM) supplies, one at +5V and
the other at +3.3V. These two supplies operate at either
200kHz or 300kHz, allowing extremely small external
components to be used. Output current capability
depends on external components, and can exceed 5A

on each supply. A 15V high-side (VDD) supply is also
provided, delivering an output current that can exceed
300mA, depending on the external components chosen.
Two linear regulators supplied by the 15V VDD line cre­ate programmable VPP supplies for PCMCIA slots.
These supplies (VPPA, VPPB) can be programmed to be
grounded or high impedance, or to deliver 5V or 12V at
up to 60mA.

An internal 5V, 25mA supply (VL) and a 3.3V, 5mA ref­erence voltage (REF) are also generated, as shown in
Figure 2. Fault-protection circuitry shuts off the PWM
and high-side supply when the internal supplies lose
regulation.

Three precision comparators are included. Their out­put stages permit them to be used as level translators
for driving high-side external power MOSFETs: For
example, to facilitate switching VCC lines to PCMCIA
slots.

8 _______________________________________________________________________________________

Triple-Output Power-Supply

Controller for Notebook Computers

MAX782

BATTERY INPUT

5.5V TO 30V
(NOTE 1)

VPP

CONTROL

INPUTS

R1

+3.3V at 3A

C14

150µF

N1-N4 = Si9410DY
NOTE 1: BATTERY VOLTAGE RANGE 6.5V to 30V 
WITH COMPONENTS SHOWN
SEE
NOTE 2: SEE FIGURE 5.

25mΩ

C7

150µF

+3.3V ON/OFF

+5V ON/OFF

OSC SYNC

LOW-VOLTAGE (6-CELL) OPERATION

L1

10µH

1N5819

C1
33µF

N1

D3

(NOTE 2)

0.1µF

N3

0.01µF

D1A

1N4148

C5

C9

SECTION.

29 28

V+ VL

16
15

DA1

18

DB0

17

DB1

MAX782

31

BST3

33

DH3

32

LX3

30

DL3

35

CS3

34

FB3

36

SS3

1

ON3

19

ON5

14

SYNC

GND REF PGND

12 13 26

D1-D3
Q1-Q3

C3
1µF

VPPADA0

VPPB

VDD

BST5

DH5

LX5

DL5
CS5

FB5
SS5

C13

+5V at 3A

C6
330µF

33µF



C2

D1B
1N4148

4.7µF
C11

1µF

C4

0.1µF

C8

0.01µF

3
3

C10
1µF

N4

(NOTE 2)

9

11

10

24
22
23
25
21
27
20
5

VH

2, 3, 4
8, 7, 6

+5V at 5mA

0V, 5V, 12V

0V, 5V, 12V

+15V AT 300mA, SEE 

HIGH-SIDE SUPPLY (VDD)

D2

EC11FS1

1:2.2

N2

L2 10µH

D4

1N5819

COMPARATOR SUPPLY INPUT
COMPARATOR INPUTS
COMPARATOR OUTPUTS

SECTION.

C12

2.2µF

3.3V AT 5mA

R2

20mΩ

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.

_______________________________________________________________________________________ 9

The +5V output is produced by a current-mode PWM

+5V Supply

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 VINapproaches
5V, the +5V output gracefully falls with VINuntil 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.

Triple-Output Power-Supply
Controller for Notebook Computers

V+

VL

MAX782

REF

GND

SYNC

VPPA

DA0
DA1

VPPB

DB0
DB1

D3

5V

3.3V

1.65V

+5V LDO

LINEAR 

REGULATOR

+3.3V

REFERENCE

300kHz/200kHz

OSCILLATOR

LINEAR

REGULATOR

LINEAR

REGULATOR

2.8V

P

3.3V

PWM

CONTROLLER



(SEE FIG. 3)

ON

5V

PWM

CONTROLLER

(SEE FIG. 3)

ON

4.5V

4V

STANDBY

ON

13V TO 19V


FAULT

VDD REG

13V

FB3
CS3
BST3
DH3
LX3
DL3
SS3

PGND

ON3

FB5
CS5
BST5
DH5
LX5
DL5
SS5

ON5

VDD

19V

Q3

D2

1.65V

D1

1.65V

VH

Figure 2. MAX782 Block Diagram

10 ______________________________________________________________________________________

Q2

Q1