19-0160; Rev 2; 4/97
IT
TION K
ED
VALUA
E
INCLUD
ATION
INFORM
Dual-Output Power-Supply
Controller for Notebook Computers
________________________________Features
o
Dual PWM Buck Controllers (+3.3V and +5V)
o
Two Precision Comparators or Level Translators
o
95% Efficiency
o
420µA Quiescent Current, 70µA in Standby
(linear regulators alive)
o
25µA Shutdown Current (+5V linear alive)
o
5.5V to 30V Input Range
o
Small SSOP Package
o
Fixed Output Voltages:
3.3V (standard)
3.45V (High-Speed Pentium™)
3.6V (PowerPC™)
__________________General Description
The MAX786 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. Other features include dual,
low-dropout, micropower linear regulators for
CMOS/RTC back-up, and two precision low-battery-
detection comparators.
High efficiency (95% at 2A; greater than 80% at loads
from 5mA to 3A) is achieved through synchronous recti-
fication and PWM operation at heavy loads, and
Idle Mode
TM
operation 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 load-
transient responses are terrific, with a high 60kHz unity-
gain crossover frequency allowing output transients to
be corrected within four or five clock cycles. Low sys-
tem 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 synchro-
nizable oscillator for noise-sensitive applications such
as electromagnetic pen-based systems and communi-
cating computers. The MAX786 is a monolithic,
BiCMOS IC available in fine-pitch, surface-mount
SSOP packages.
MAX786
_________________Ordering Information
PART
MAX786CAI
MAX786RCAI
TEMP. RANGE
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
28 SSOP
28 SSOP
V
OUT
3.3V
3.45V
Ordering Information continued at end of data sheet.
_____________________Pin Configuration
TOP VIEW
CS3
1
SS3
2
ON3
3
D1
4
D2
5
VH
6
28
FB3
27
DH3
26
LX3
25
BST3
___________________________Applications
Notebook Computers
Portable Data Terminals
Communicating Computers
Pen-Entry Systems
MAX786
24
DL3
23
V+
22
VL
21
FB5
20
PGND
19
DL5
18
BST5
17
LX5
16
DH5
15
CS5
________Typical Application Diagram
+3.3V
5.5V
TO
30V
SHUTDOWN
5V ON/OFF
3.3V ON/OFF
SYNC
POWER
SECTION
µP
MEMORY
+5V PERIPHERALS
Q2
7
Q1
8
GND
9
REF
10
SYNC
11
SHDN
12
ON5
13
SS5
14
MAX786
POWER-GOOD
LOW-BATTERY WARNING
SUSPEND POWER
SSOP
Idle Mode is a trademark of Maxim Integrated Products. Pentium is a trademark of Intel Corp. PowerPC is a trademark of IBM Corp.
_______________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Dual-Output Power-Supply
Controller for Notebook Computers
MAX786
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
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, I
VL
= 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.)
PARAMETER
3.3V AND 5V STEP-DOWN CONTROLLERS
Input Supply Range
FB5 Output Voltage
0mV < (CS5-FB5) < 70mV, 6V < V + < 30V
(includes load and line regulation)
0mV < (CS3-FB3) < 70mV, 6V < V + < 30V
(includes load and line regulation)
MAX786
MAX786R
MAX786S
CONDITIONS
MIN
5.5
4.80
3.17
3.32
3.46
5.08
3.35
3.50
3.65
2.5
0.03
100
4.0
TYP
MAX
30
5.20
3.46
3.60
3.75
UNITS
V
V
FB3 Output Voltage
V
%
%/V
mV
µA
mA
V
V
V
V
V
mV
µA
µA
mW
µA
V
nA
Load Regulation
Either controller (CS_ -FB_ = 0mV to 70mV)
Line Regulation
Either controller (V+ = 6V to 30V)
Current-Limit Voltage
CS3-FB3 or CS5-FB5
SS3/SS5 Source Current
SS3/SS5 Fault Sink Current
INTERNAL REGULATOR AND REFERENCE
VL Output Voltage
ON5 = ON3 = 0V, 5.5V < V+ < 30V, 0mA < I
L
< 25mA
VL Fault Lockout Voltage
Falling edge, hysteresis = 1%
VL/FB5 Switchover Voltage
Rising edge of FB5, hysteresis = 1%
REF Output Voltage
No external load (Note 1)
REF Fault Lockout Voltage
Falling edge
REF Load Regulation
0mA < I
L
< 5mA (Note 2)
–— –
— —
SHDN = D1 = D2 = ON3 = ON5 = 0V, V+ = 30V
V+ Shutdown Current
V+ Standby Current
D1 = D2 = ON3 = ON5 = 0V, V+ = 30V
Quiescent Power Consumption
(both PWM controllers on)
V+ Off Current
COMPARATORS
D1, D2 Trip Voltage
D1, D2 Input Current
D1 = D2 = 0V, FB5 = CS5 = 5.25V,
FB3 = CS3 = 3.5V
FB5 = CS5 = 5.25V, VL switched over to FB5
Falling edge, hysteresis = 1%
D1 = D2 = 0V, 5V
80
2.5
2
4.5
3.6
4.2
3.24
2.4
120
6.5
30
25
70
5.5
30
1.61
5.5
4.2
4.7
3.36
3.2
75
40
120
8.6
60
1.69
±100
2
________________________________________________________________________________________________
Dual-Output Power-Supply
Controller for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, GND = PGND = 0V, I
VL
= 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.)
PARAMETER
Q1, Q2 Source Current
Q1, Q2 Sink Current
Q1, Q2 Output High Voltage
Q1, Q2 Output Low Voltage
Quiescent VH Current
CONDITIONS
VH = 15V, V
OUT
= 2.5V
VH = 15V, V
OUT
= 2.5V
I
SOURCE
= 5µA, VH = 3V
I
SINK
= 20µA, VH = 3V
VH = 18V, D1 = D2 = 5V, no external load
SYNC = 3.3V
SYNC = 0V, 5V
SYNC High Pulse Width
SYNC Low Pulse Width
SYNC Rise/Fall Time
Oscillator SYNC Range
Maximum Duty Cycle
Input Low Voltage
Input High Voltage
Input Current
DL3/DL5 Sink/Source Current
DH3/DH5 Sink/Source Current
DL3/DL5 On-Resistance
DH3/DH5 On-Resistance
SYNC = 3.3V
SYNC = 0V or 5V
SHDN, ON3, ON5, SYNC
SHDN, ON3, ON5
SYNC
SHDN, ON3, ON5 V
IN
= 0V, 5V
V
OUT
= 2V
BST3-LX3 = BST5-LX5 = 4.5V, V
OUT
= 2V
High or low
High or low, BST3-LX3 = BST5-LX5 = 4.5V
1
1
7
7
2.4
VL - 0 .5
±1
µA
A
A
Ω
Ω
Not tested
240
89
92
92
95
0.8
V
V
270
170
200
200
200
350
4
300
200
MIN
12
200
VH - 0 .5
0.4
10
330
230
ns
ns
ns
kHz
%
TYP
20
500
MAX
30
1000
UNITS
µA
µA
V
V
µA
MAX786
OSCILLATOR AND INPUTS/OUTPUTS
Oscillator Frequency
kHz
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. AV
CL
for the +3.3V supply is unity gain.
AV
CL
for the +5V supply is 1.54.
_________________________________________________________________________________________________
3
Dual-Output Power-Supply
Controller for Notebook Computers
MAX786
________________________________________________Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. +5V OUTPUT
CURRENT, 200kHz
100
VIN = 6V
VIN = 30V
EFFICIENCY (%)
VIN = 15V
100
EFFICIENCY vs. +5V OUTPUT
CURRENT, 300kHz
100
EFFICIENCY vs. +3.3V OUTPUT
CURRENT, 200kHz
VIN = 15V
90
VIN = 6V
EFFICIENCY (%)
VIN = 15V
80
VIN = 30V
70
+3.3V OFF
60
90
VIN = 6V
80
VIN = 30V
90
EFFICIENCY (%)
80
70
SYNC = 0V, +3.3V OFF
60
70
60
SYNC = 0V, +5V ON
50
1m
10m
100m
1
+5V OUTPUT CURRENT (A)
10
50
1m
10m
100m
1
+5V OUTPUT CURRENT (A)
10
50
1m
10m
100m
1
10
+3.3V OUTPUT CURRENT (A)
EFFICIENCY vs. +3.3V OUTPUT
CURRENT, 300kHz
100
QUIESCENT SUPPLY CURRENT (mA)
VIN = 15V
90
EFFICIENCY (%)
VIN = 6V
80
70
+5V ON
60
VIN = 30V
19
QUIESCENT SUPPLY CURRENT vs.
SUPPLY VOLTAGE
2.5
STANDBY SUPPLY CURRENT (mA)
STANDBY SUPPLY CURRENT vs.
SUPPLY VOLTAGE
18
ON3 = ON5 = HIGH
2
2.0
1.5
ON3 = ON5 = 0V
1.0
1
0.5
50
1m
10m
100m
1
10
+3.3V OUTPUT CURRENT (A)
0
0
6
12
18
24
30
SUPPLY VOLTAGE (V)
0
0
6
12
18
SUPPLY VOLTAGE (V)
24
30
SHUTDOWN SUPPLY CURRENT vs.
SUPPLY VOLTAGE
500
MINIMUM VIN TO VOUT DIFFERENTIAL (V)
SHUTDOWN SUPPLY CURRENT (µA)
1.0
MINIMUM VIN TO VOUT DIFFERENTIAL
vs. +5V OUTPUT CURRENT
1000
SWITCHING FREQUENCY (kHz)
SWITCHING FREQUENCY vs.
LOAD CURRENT
SYNC = REF (300kHz)
ON3 = ON5 = 5V
100
+5V, V
IN
= 7.5V
400
0.8
300kHz
300
SHDN = 0V
200
0.6
10
+5V, V
IN
= 30V
0.4
200kHz
+5V OUTPUT
STILL REGULATING
1
+3.3V, V
IN
= 7.5V
100
0.2
0
0
6
12
18
24
SUPPLY VOLTAGE (V)
30
0
1m
10m
100m
1
10
+5V OUTPUT CURRENT (A)
0.1
100µ
1m
10m
100m
1
LOAD CURRENT (A)
4
_______________________________________________________________________________________
Dual-Output Power-Supply
Controller for Notebook Computers
_________________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
IDLE MODE WAVEFORMS
PULSE-WIDTH MODULATION MODE WAVEFORMS
MAX786
+5V OUTPUT
50mV/div
LX 10V/div
2V/div
+5V OUTPUT
50mV/div
200µs/div
I
LOAD
= 100mA
V
IN
= 10V
500ns/div
+5V OUTPUT CURRENT = 1A
V
IN
= 16V
+5V LOAD-TRANSIENT RESPONSE
+3.3V LOAD-TRANSIENT RESPONSE
3A
0A
LOAD CURRENT
3A
0A
LOAD CURRENT
+5V OUTPUT
50mV/div
+3.3V OUTPUT
50mV/div
200µs/div
V
IN
= 15V
200µs/div
V
IN
= 15V
_______________________________________________________________________________________
5
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