19-3262; Rev 0; 4/04
500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
MAX8741/MAX8742
General Description
The MAX8741/MAX8742 are buck-topology, step-down,
switch-mode, power-supply controllers that generate
logic-supply voltages in battery-powered systems. These
high-performance, dual/triple-output devices include on-
board power-up sequencing, power-good signaling with
delay, digital soft-start, secondary winding control, low-
dropout circuitry, internal frequency-compensation net-
works, and automatic bootstrapping.
Up to 97% efficiency is achieved through synchronous
rectification and Maxim’s proprietary Idle Mode™ control
scheme. Efficiency is greater than 80% over a 1000:1
load-current range, which extends battery life in system
suspend or standby mode. Excellent dynamic response
corrects output load transients within five clock cycles.
Strong 1A on-board gate drivers ensure fast external
n-channel MOSFET switching.
These devices feature a logic-controlled and synchroniz-
able, fixed-frequency, pulse-width-modulation (PWM)
operating mode. This reduces noise and RF interference
in sensitive mobile communications and pen-entry appli-
cations. Asserting the
SKIP
pin enables fixed-frequency
mode, for lowest noise under all load conditions.
The MAX8741/MAX8742 include two PWM regulators,
adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V
modes. All these devices include secondary feedback
regulation, and the MAX8742 contains a 12V/120mA lin-
ear regulator. The MAX8741 includes a secondary feed-
back input (SECFB), plus a control pin (STEER) that
selects which PWM (3.3V or 5V) receives the secondary
feedback signal. SECFB provides a method for adjusting
the secondary winding voltage regulation point with an
external resistor-divider, and is intended to aid in creating
auxiliary voltages other than fixed 12V.
The MAX8741/MAX8742 contain internal output overvolt-
age- and undervoltage-protection features.
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Features
97% Efficiency
4.2V to 30V Input Range
2.5V to 5.5V Dual Adjustable Outputs
Selectable 3.3V and 5V Fixed or Adjustable
Outputs (Dual Mode™)
12V Linear Regulator
Adjustable Secondary Feedback (MAX8741)
5V/50mA Linear-Regulator Output
Precision 2.5V Reference Output
Programmable Power-Up Sequencing
Power-Good (RESET) Output
Output Overvoltage Protection
Output Undervoltage Shutdown
333kHz/500kHz Low-Noise, Fixed-Frequency
Operation
Low-Dropout, 98% Duty-Factor Operation
2.5mW Typical Quiescent Power (12V Input,
Both SMPSs On)
4µA Typical Shutdown Current
Ordering Information
PART
MAX8741EAI
MAX8741ETJ
MAX8742EAI
MAX8742ETJ
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
32 Thin QFN 5mm x 5mm
28 SSOP
32 Thin QFN 5mm x 5mm
Functional Diagram
INPUT
5V (RTC)
5V
LINEAR
12V
LINEAR
12V
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC Converters
3.3V
3.3V
SMPS
5V
SMPS
5V
Idle Mode is a trademark of Maxim Integrated Products, Inc.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
ON/OFF
POWER-UP
SEQUENCE
POWER-
GOOD
RESET
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
MAX8741/MAX8742
ABSOLUTE MAXIMUM RATINGS
V+ to GND ..............................................................-0.3V to +36V
PGND to GND.....................................................................±0.3V
V
L
to GND ................................................................-0.3V to +6V
BST3, BST5 to GND ..............................................-0.3V to +36V
CSH3, CSH5 to GND................................................-0.3V to +6V
FB3 to GND ..............................................-0.3V to (CSL3 + 0.3V)
FB5 to GND ...............................................-0.3V to (CSL5 +0.3V)
LX3 to BST3..............................................................-6V to +0.3V
LX5 to BST5..............................................................-6V to +0.3V
REF, SYNC, SEQ, STEER,
SKIP,
TIME/ON5, SECFB,
RESET
to GND ..........-0.3V to (V
L
+ 0.3V)
V
DD
to GND. ...........................................................-0.3V to +20V
RUN/ON3,
SHDN
to GND.............................-0.3V to (V+ + 0.3V)
12OUT to GND ..........................................-0.3V to (V
DD
+ 0.3V)
DL3, DL5 to PGND........................................-0.3V to (V
L
+ 0.3V)
DH3 to LX3 ..............................................-0.3V to (BST3 + 0.3V)
DH5 to LX5 ..............................................-0.3V to (BST5 + 0.3V)
V
L
, REF Short to GND ................................................Momentary
12OUT Short to GND..................................................Continuous
REF Current...........................................................+5mA to -1mA
V
L
Current.........................................................................+50mA
12OUT Current . .............................................................+200mA
V
DD
Shunt Current. ...........................................................+15mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin SSOP (derate 9.52mW/°C above +70°C) ........762mW
32-Pin Thin QFN (derate 21.3mW/°C above +70°C) ....1702mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range ............................-65°C to +160°C
Lead Temperature (soldering, 10s) ................................+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, both PWMs on, SYNC = V
L
, V
L
load = 0, REF load = 0,
SKIP
= 0,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
MAIN SMPS CONTROLLERS
Input Voltage Range
3V Output Voltage in Adjustable Mode
3V Output Voltage in Fixed Mode
5V Output Voltage in Adjustable Mode
5V Output Voltage in Fixed Mode
Output Voltage Adjust Range
Adjustable-Mode Threshold Voltage
Load Regulation
Line Regulation
Current-Limit Threshold
Idle-Mode Threshold
Soft-Start Ramp Time
Oscillator Frequency
V+ = 4.2V to 30V, CSH3 - CSL3 = 0,
CSL3 connected to FB3
V+ = 4.2V to 30V, 0 < CSH3 - CSL3
< 80mV, FB3 = 0
V+ = 4.2V to 30V, CSH5 - CSL5 = 0,
CSL5 connected to FB5
V+ = 5.3V to 30V, 0 < CSH5 - CSL5
< 80mV, FB5 = 0
Either SMPS
Dual-mode comparator
Either SMPS, 0 < CSH_ - CSL_ < 80mV
Either SMPS, 5.2V < V+ < 30V
CSH3 - CSL3 or CSH5 - CSL5
SKIP
= V
L
or V
DD
< 13V or SECFB < 2.44V
SKIP
= 0, not tested
From enable to 95% full current limit with
respect to f
OSC
(Note 1)
SYNC = V
L
SYNC = 0
450
283
80
-50
10
4.2
2.42
3.20
2.42
4.85
REF
0.5
-2
0.03
100
-100
25
512
500
333
550
383
120
-150
40
2.5
3.39
2.5
5.13
30.0
2.58
3.47
2.58
5.25
5.5
1.1
V
V
V
V
V
V
V
%
%/V
mV
mV
Clks
kHz
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, both PWMs on, SYNC = V
L
, V
L
load = 0, REF load = 0,
SKIP
= 0,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
Maximum Duty Factor
SYNC Input High Pulse Width
SYNC Input Low Pulse Width
SYNC Rise/Fall Time
SYNC Input-Frequency Range
Current-Sense Input Leakage Current
FLYBACK CONTROLLER
V
DD
Regulation Threshold
SECFB Regulation Threshold
DL Pulse Width
V
DD
Shunt Threshold
V
DD
Shunt Sink Current
V
DD
Leakage Current
12V LINEAR REGULATOR
(MAX8742)
12OUT Output Voltage
12OUT Current Limit
Quiescent V
DD
Current
INTERNAL REGULATOR AND REFERENCE
V
L
Output Voltage
V
L
Undervoltage-Lockout Fault Threshold
V
L
Switchover Threshold
REF Output Voltage
REF Load Regulation
REF Sink Current
REF Fault-Lockout Voltage
V+ Operating Supply Current
V+ Standby Supply Current
V+ Standby Supply Current in Dropout
V+ Shutdown Supply Current
Falling edge
V
L
switched over to CSL5, 5V SMPS on
V+ = 5.5V to 30V, both SMPSs off, includes
current into
SHDN
V+ = 4.2V to 5.5V, both SMPSs off, includes
current into
SHDN
V+ = 4.0V to 30V,
SHDN
= 0
Both SMPSs enabled,
FB3 = FB5 = 0,
CSL3 = CSH3 = 3.5V,
CSL5 = CSH5 = 5.3V
MAX8742
MAX8741
SHDN
= V+, RUN/ON3 = TIME/ON5 = 0,
5.4V < V+ < 30V, 0mA < I
LOAD
< 50mA
Falling edge, hysteresis = 1%
Rising edge of CSL5, hysteresis = 1%
No external load (Note 4)
0 < I
LOAD
< 50µA
0 < I
LOAD
< 5mA
10
1.8
5
30
50
4
2.5
1.5
2.4
50
60
200
10
4
mW
4
4.7
3.5
4.2
2.45
3.6
4.5
2.5
5.1
3.7
4.7
2.55
12.5
100.0
V
V
V
V
mV
µA
V
µA
µA
µA
µA
13V < V
DD
< 18V, 0 < I
LOAD
< 120mA
12OUT forced to 11V, V
DD
= 13V
V
DD
= 18V, run mode, no 12OUT load
11.65
12.10
150
50
100
12.50
V
mA
µA
Falling edge (MAX8742)
Falling edge (MAX8741)
V
DD
< 13V or SECFB < 2.44V
Rising edge, hysteresis = 1% (MAX8742)
V
DD
= 20V (MAX8742)
V
DD
= 5V, off mode (Note 3)
18
10
30
13
2.44
0.75
20
14
2.60
V
V
µs
V
mA
µA
V+ = V
L
= 0,
CSL3 = CSH3 = CSL5 = CSH5 = 5.5V
SYNC = V
L
SYNC = 0 (Note 2)
Not tested
Not tested
Not tested
400
0.01
CONDITIONS
MIN
95
96.5
200
200
200
583
10
TYP
97
98
MAX
UNITS
%
ns
ns
ns
kHz
µA
MAX8741/MAX8742
Quiescent Power Consumption
_______________________________________________________________________________________
3
500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
MAX8741/MAX8742
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, both PWMs on, SYNC = V
L
, V
L
load = 0, REF load = 0,
SKIP
= 0,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
FAULT DETECTION
Overvoltage Trip Threshold
Overvoltage Fault Propagation Delay
Output Undervoltage Threshold
Output Undervoltage-Lockout Time
Thermal-Shutdown Threshold
RESET
RESET
Trip Threshold
RESET
Propagation Delay
RESET
Delay Time
INPUTS AND OUTPUTS
Feedback-Input Leakage Current
Logic Input-Low Voltage
Logic Input-High Voltage
Input Leakage Current
Logic Output-Low Voltage
Logic Output-High Current
TIME/ON5 Input Trip Level
TIME/ON5 Source Current
TIME/ON5 On-Resistance
Gate-Driver Sink/Source Current
Gate-Driver On-Resistance
FB3, FB5; SECFB = 2.6V
RUN/ON3,
SKIP,
TIME/ON5 (SEQ = REF),
SHDN,
STEER, SYNC
RUN/ON3,
SKIP,
TIME/ON5 (SEQ = REF),
SHDN,
STEER, SYNC
RUN/ON3,
SKIP,
TIME/ON5 (SEQ = REF),
SHDN,
STEER, SYNC, SEQ; V
PIN
= 0V or 3.3V
RESET,
I
SINK
= 4mA
RESET
= 3.5V
SEQ = 0 or V
L
TIME/ON5 = 0, SEQ = 0 or V
L
TIME/ON5; RUN/ON3 = 0, SEQ = 0 or V
L
DL3, DH3, DL5, DH5; forced to 2V
High or low (Note 5)
SSOP package
QFN package
1
2.4
2.5
3
15
1
1.5
1.5
7
8
2.6
3.5
80
2.4
±1
0.4
1
50
0.6
nA
V
V
µA
V
mA
V
µA
Ω
A
Ω
With respect to unloaded output voltage,
falling edge; typical hysteresis = 1%
Falling edge, CSL_ driven 2% below
RESET
trip threshold
With respect to f
OSC
27,000
-7
-5.5
1.5
32,000
37,000
-4
%
µs
Clks
With respect to unloaded output voltage
CSL_ driven 2% above overvoltage trip
threshold
With respect to unloaded output voltage
From each SMPS enabled, with respect to
f
OSC
Typical hysteresis = 10°C
60
3300
4
7
1.5
70
4096
+150
80
4700
10
%
µs
%
Clks
°C
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
MAX8741/MAX8742
ELECTRICAL CHARACTERISTICS
(V+ = 15V, both PWMs on, SYNC = V
L
, V
L
load = 0, REF load = 0,
SKIP
= 0,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 6)
PARAMETER
MAIN SMPS CONTROLLERS
Input Voltage Range
3V Output Voltage in Adjustable Mode
3V Output Voltage in Fixed Mode
5V Output Voltage in Adjustable Mode
5V Output Voltage in Fixed Mode
Output Voltage Adjust Range
Adjustable-Mode Threshold Voltage
Current-Limit Threshold
Oscillator Frequency
Maximum Duty Factor
SYNC Input Frequency Range
FLYBACK CONTROLLER
V
DD
Regulation Threshold
SECFB Regulation Threshold
V
DD
Shunt Threshold
V
DD
Shunt Sink Current
12V LINEAR REGULATOR
(MAX8742)
12OUT Output Voltage
Quiescent V
DD
Current
INTERNAL REGULATOR AND REFERENCE
V
L
Output Voltage
V
L
Undervoltage-Lockout Fault Threshold
V
L
Switchover Threshold
REF Output Voltage
REF Load Regulation
REF Sink Current
REF Fault-Lockout Voltage
V+ Operating Supply Current
Falling edge
V
L
switched over to CSL5, 5V SMPS on
SHDN
= V+, RUN/ON3 = TIME/ON5 = 0,
5.4V < V+ < 30V, 0 < I
LOAD
< 50mA
Falling edge, hysteresis = 1%
Rising edge of CSL5, hysteresis = 1%
No external load (Note 4)
0 < I
LOAD
< 50µA
0 < I
LOAD
< 5mA
10
1.8
2.4
50
4.7
3.5
4.2
2.45
5.1
3.7
4.7
2.55
12.5
100.0
V
V
V
V
mV
µA
V
µA
13V < V
DD
< 18V, 0mA < I
LOAD
< 100mA
V
DD
= 18V, run mode, no 12OUT load
11.65
12.50
100
V
µA
Falling edge (MAX8742)
Falling edge (MAX8741)
Rising edge, hysteresis = 1% (MAX8742)
V
DD
= 20V (MAX8742)
13
2.44
18
10
14
2.60
20
V
V
V
mA
V+ = 4.2V to 30V, CSH3 - CSL3 = 0,
CSL3 connected to FB3
V+ = 4.2V to 30V, 0 < CSH3 - CSL3
< 80mV, FB3 = 0
V+ = 4.2V to 30V, CSH5 - CSL5 = 0,
CSL5 connected to FB5
V+ = 5.3V to 30V, 0 < CSH5 - CSL5
< 80mV, FB5 = 0
Either SMPS
Dual-mode comparator
CSH3 - CSL3 or CSH5 - CSL5
SKIP
= V
L
or V
DD
< 13V or SECFB < 2.44V
SYNC = V
L
SYNC = 0
SYNC = V
L
SYNC = 0 (Note 2)
4.2
2.42
3.20
2.42
4.85
REF
0.5
80
-50
450
283
95
97
400
583
30.0
2.58
3.47
2.58
5.25
5.5
1.1
120
-150
550
383
V
V
V
V
V
V
V
mV
kHz
%
kHz
CONDITIONS
MIN
TYP
MAX
UNITS
_______________________________________________________________________________________
5
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