Rainbow Electronics MAX786 User Manual

__________________General Description

The MAX786 is a system-engineered power-supply
controller for notebook computers or similar battery­powered equipment. It provides two high-performance
step-down (buck) pulse-width modulators (PWMs)
for +3.3V and +5V. Other features include dual,
low-dropout, micropower linear regulators for
CMOS/RTC back-up, and two precision low-battery­detection 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
Idle ModeTMoperation at light loads. The MAX786 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 load­transient responses are terrific, with a high 60kHz unity­gain 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.

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 MAX786 is a monolithic,
BiCMOS IC available in fine-pitch, surface-mount
SSOP packages.

___________________________Applications

Notebook Computers
Portable Data Terminals
Communicating Computers
Pen-Entry Systems

________________________________Features

♦ Dual PWM Buck Controllers (+3.3V and +5V)
♦ Two Precision Comparators or Level Translators
♦ 95% Efficiency
♦ 420µA Quiescent Current, 70µA in Standby

(linear regulators alive)

♦ 25µA Shutdown Current (+5V linear alive)
♦ 5.5V to 30V Input Range
♦ Small SSOP Package
♦ Fixed Output Voltages:

3.3V (standard)

3.45V (High-Speed Pentium

™)

3.6V (PowerPC™)

_________________Ordering Information

MAX786

Dual-Output Power-Supply

Controller for Notebook Computers

_______________________________________________________________________

Maxim Integrated Products

1

19-0160; Rev 2; 4/97

_____________________Pin Configuration

28
27
26
25
24
23
22
21

1
2
3
4
5
6
7
8

FB3
DH3
LX3
BST3

D1

ON3

SS3

CS3

TOP VIEW

DL3
V+
VL

FB5

Q1

Q2

VH

D2

20
19
18
17

9
10
11
12

PGND
DL5
BST5
LX5

SHDN

SYNC

REF

GND

SSOP

MAX786

16
15

13
14

DH5
CS5

SS5

ON5

Idle Mode is a trademark of Maxim Integrated Products. Pentium is a trademark of Intel Corp. PowerPC is a trademark of IBM Corp.

________Typical Application Diagram

MAX786

5.5V
TO

30V

SHUTDOWN

POWER

SECTION

POWER-GOOD

LOW-BATTERY WARNING

µP
MEMORY
PERIPHERALS

+3.3V

+5V

5V ON/OFF

3.3V ON/OFF
SYNC

SUSPEND POWER

28 SSOP0°C to +70°CMAX786RCAI

28 SSOP0°C to +70°CMAX786CAI

PIN-PACKAGETEMP. RANGEPART

3.45V

3.3V

V

OUT

Ordering Information continued at end of data sheet.

EVALUATION KIT

INFORMATION INCLUDED

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone].

MAX786

Dual-Output Power-Supply
Controller for Notebook Computers

2 ________________________________________________________________________________________________

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

REF

= 0mA,

SHDN

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

T

A

= T

MIN

to T

MAX

, unless otherwise noted.)

ABSOLUTE MAXIMUM RATINGS

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

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

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

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

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

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

Inputs/Outputs to GND

(D1, D2,

SHDN

, ON5, REF, SS5, CS5,

FB5, SYNC, CS3,FB3, SS3, ON3)............-0.3V to (VL + 0.3V)

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

Q1, Q2 to GND............................................-0.3V to (VH + 0.3V)

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

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

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

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

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

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

Continuous Power Dissipation (T

A

= +70°C)

SSOP (derate 9.52mW/°C above +70°C)....................762mW

Operating Temperature Ranges

MAX786CAI/MAX786_CAI .................................0°C to +70°C

MAX786EAI/MAX786_EAI...............................-40°C to +85°C

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

MAX786S

MAX786R

MAX786

FB3 Output Voltage

3.46 3.65 3.75

V

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

3.32 3.50 3.60

REF Load Regulation 30 75 mV0mA < IL< 5mA (Note 2)

PARAMETER

VL Output Voltage

MIN TYP MAX

4.5 5.5

UNITS

Current-Limit Voltage

V

80 100 120

VL Fault Lockout Voltage

mV

Line Regulation

3.6 4.2

0.03 %/V

Load Regulation 2.5

V

%

3.17 3.35 3.46

VL/FB5 Switchover Voltage

SS3/SS5 Source Current 2.5 4.0 6.5 µA

4.2 4.7 V

REF Output Voltage

SS3/SS5 Fault Sink Current 2

3.24 3.36

mA

V

REF Fault Lockout Voltage 2.4 3.2 V

Input Supply Range 5.5 30 V
FB5 Output Voltage 4.80 5.08 5.20 V

CONDITIONS

ON5 = ON3 = 0V, 5.5V < V+ < 30V, 0mA < IL< 25mA

CS3-FB3 or CS5-FB5

Falling edge, hysteresis = 1%

Either controller (V+ = 6V to 30V)

Either controller (CS_ -FB_ = 0mV to 70mV)

Rising edge of FB5, hysteresis = 1%
No external load (Note 1)

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

Falling edge

V+ Shutdown Current 25 40 µA

–S—H—D—N–

= D1 = D2 = ON3 = ON5 = 0V, V+ = 30V

V+ Standby Current 70 120 µAD1 = D2 = ON3 = ON5 = 0V, V+ = 30V
Quiescent Power Consumption

(both PWM controllers on)

5.5 8.6 mW

D1 = D2 = 0V, FB5 = CS5 = 5.25V,
FB3 = CS3 = 3.5V

V+ Off Current 30 60 µAFB5 = CS5 = 5.25V, VL switched over to FB5

D1, D2 Trip Voltage 1.61 1.69 VFalling edge, hysteresis = 1%
D1, D2 Input Current ±100 nAD1 = D2 = 0V, 5V

3.3V AND 5V STEP-DOWN CONTROLLERS

INTERNAL REGULATOR AND REFERENCE

COMPARATORS

MAX786

Dual-Output Power-Supply

Controller for Notebook Computers

_________________________________________________________________________________________________

3

Note 1: Since the reference uses VL as its supply, its V+ line regulation error is insignificant.
Note 2: The main switching outputs track the reference voltage. Loading the reference reduces the main outputs slightly according

to the closed-loop gain (AV

CL

) and the reference voltage load-regulation error. AVCLfor the +3.3V supply is unity gain.

AVCLfor the +5V supply is 1.54.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Q1, Q2 Source Current VH = 15V, V

OUT

= 2.5V 12 20 30 µA

Q1, Q2 Sink Current VH = 15V, V

OUT

= 2.5V 200 500 1000 µA

Q1, Q2 Output High Voltage I

SOURCE

= 5µA, VH = 3V VH -0.5 V

Q1, Q2 Output Low Voltage I

SINK

= 20µA, VH = 3V 0.4 V

Quiescent VH Current VH = 18V, D1 = D2 = 5V, no external load 4 10 µA

OSCILLATOR AND INPUTS/OUTPUTS

Oscillator Frequency

SYNC = 3.3V 270 300 330

kHz

SYNC = 0V, 5V 170 200 230
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

SYNC = 3.3V 89 92

%

SYNC = 0V or 5V 92 95
Input Low Voltage

SHDN

, ON3, ON5, SYNC 0.8 V

Input High Voltage

SHDN

, ON3, ON5 2.4

V

SYNC VL -0.5
Input Current

SHDN

, ON3, ON5 VIN= 0V, 5V ±1 µA

DL3/DL5 Sink/Source Current V

OUT

= 2V 1 A

DH3/DH5 Sink/Source Current BST3-LX3 = BST5-LX5 = 4.5V, V

OUT

= 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

ELECTRICAL CHARACTERISTICS (continued)

(V+ = 15V, GND = PGND = 0V, IVL= I

REF

= 0mA,

SHDN

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

T

A

= T

MIN

to T

MAX

, unless otherwise noted.)

MAX786

Dual-Output Power-Supply
Controller for Notebook Computers

4 _______________________________________________________________________________________

________________________________________________Typical Operating Characteristics

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

EFFICIENCY vs. +5V OUTPUT

CURRENT, 300kHz

EFFICIENCY (%)

50

60

70

80

90

100

1m 10m 100m 1 10

+5V OUTPUT CURRENT (A)

VIN = 6V

VIN = 15V

VIN = 30V

+3.3V OFF

EFFICIENCY vs. +3.3V OUTPUT

CURRENT, 200kHz

EFFICIENCY (%)

50

60

70

80

90

100

1m

10m 100m 1 10

+3.3V OUTPUT CURRENT (A)

VIN = 6V

VIN = 15V

VIN = 30V

SYNC = 0V, +5V ON

EFFICIENCY vs. +3.3V OUTPUT

CURRENT, 300kHz

EFFICIENCY (%)

50

60

70

80

90

100

1m 10m 100m 1 10

+3.3V OUTPUT CURRENT (A)

VIN = 6V

VIN = 15V

VIN = 30V

+5V ON

SHUTDOWN SUPPLY CURRENT vs.

SUPPLY VOLTAGE

SHUTDOWN SUPPLY CURRENT (µA)

0

100

200

300

400

500

0

6 12 18 24 30

SUPPLY VOLTAGE (V)

SHDN = 0V

QUIESCENT SUPPLY CURRENT vs.

SUPPLY VOLTAGE

QUIESCENT SUPPLY CURRENT (mA)

0

1

2

18

19

0 6 12 18 24 30

SUPPLY VOLTAGE (V)

ON3 = ON5 = HIGH

STANDBY SUPPLY CURRENT vs.

SUPPLY VOLTAGE

STANDBY SUPPLY CURRENT (mA)

0

0.5

1.0

1.5

2.0

2.5

0 6 12 18 24 30

ON3 = ON5 = 0V

SUPPLY VOLTAGE (V)

MINIMUM VIN TO V

OUT

DIFFERENTIAL

vs. +5V OUTPUT CURRENT

MINIMUM V

IN

TO V

OUT

DIFFERENTIAL (V)

+5V OUTPUT CURRENT (A)

0

0.2

0.4

0.6

0.8

1.0

1m 10m 100m 1 10

300kHz

200kHz

+5V OUTPUT
STILL REGULATING

EFFICIENCY vs. +5V OUTPUT

CURRENT, 200kHz

EFFICIENCY (%)

50

60

70

80

90

100

1m 10m 100m 1 10

+5V OUTPUT CURRENT (A)

VIN = 6V

VIN = 30V

VIN = 15V

SYNC = 0V, +3.3V OFF

1000

0.1
100µ 10m 1

SWITCHING FREQUENCY vs.

LOAD CURRENT

10

LOAD CURRENT (A)

SWITCHING FREQUENCY (kHz)

100

1m 100m

SYNC = REF (300kHz)
ON3 = ON5 = 5V

+5V, VIN = 7.5V

1

+5V, VIN = 30V

+3.3V, VIN = 7.5V

200µs/div
I

LOAD

= 100mA

V

IN

= 10V

IDLE MODE WAVEFORMS

+5V OUTPUT
50mV/div

2V/div

MAX786

Dual-Output Power-Supply

Controller for Notebook Computers

_______________________________________________________________________________________ 5

500ns/div

+5V OUTPUT CURRENT = 1A

V

IN

= 16V

PULSE-WIDTH MODULATION MODE WAVEFORMS

LX 10V/div

+5V OUTPUT
50mV/div

200µs/div
V

IN

= 15V

+3.3V LOAD-TRANSIENT RESPONSE

+3.3V OUTPUT
50mV/div

3A
0A

LOAD CURRENT

200µs/div
V

IN

= 15V

+5V LOAD-TRANSIENT RESPONSE

+5V OUTPUT
50mV/div

3A
0A

LOAD CURRENT

_________________________________Typical Operating Characteristics (continued)

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

MAX786

Dual-Output Power-Supply
Controller for Notebook Computers

6 _______________________________________________________________________________________

_________________________________Typical Operating Characteristics (continued)

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

20µs/div

I

LOAD

= 2A

+5V LINE-TRANSIENT RESPONSE, RISING

VIN, 10V TO 16V
2V/div

+5V OUTPUT
50mV/div

20µs/div

I

LOAD

= 2A

+5V LINE-TRANSIENT RESPONSE, FALLING

VIN, 16V TO 10V
2V/div

+5V OUTPUT
50mV/div

20µs/div

I

LOAD

= 2A

+3.3V LINE-TRANSIENT RESPONSE, RISING

+3.3V OUTPUT
50mV/div

V

IN

, 10V TO 16V

2V/div

20µs/div

I

LOAD

= 2A

+3.3V LINE-TRANSIENT RESPONSE, FALLING

+3.3V OUTPUT
50mV/div

V

IN

, 16V TO 10V

2V/div