__________________General Description
The MAX730A/MAX738A/MAX744A are 5V-output
CMOS, step-down switching regulators. The MAX738A/
MAX744A accept inputs from 6V to 16V and deliver
750mA. The MAX744A guarantees 500mA load capa-
bility for inputs above 6V and has tighter oscillator fre-
quency limits for low-noise (radio) applications. The
MAX730A accepts inputs between 5.2V and 11V and
delivers 450mA for inputs above 6V. Typical efficien-
cies are 85% to 96%. Quiescent supply current is
1.7mA and only 6A in shutdown.
Pulse-width modulation (PWM) current-mode control
provides precise output regulation and excellent tran-
sient responses. Output voltage accuracy is guaran-
teed to be 5% over line, load, and temperature varia-
tions. Fixed-frequency switching allows easy filtering of
output ripple and noise, as well as the use of small
external components. These regulators require only a
single inductor value to work in most applications, so
no inductor design is necessary.
The MAX730A/MAX738A/MAX744A also feature cycle-
by-cycle current limiting, overcurrent limiting, undervolt-
age lockout, and programmable soft-start protection.
___________________________Applications
Portable Instruments
Cellular Phones and Radios
Personal Communicators
Distributed Power Systems
Computer Peripherals
________________________________Features
o
750mA Load Currents (MAX738A/MAX744A)
o
High-Frequency, Current-Mode PWM
o
159kHz to 212.5kHz Guaranteed Oscillator
Frequency Limits (MAX744A)
o
85% to 96% Efficiencies
o
1.7mA Quiescent Current
o
6A Shutdown Supply Current
o
Single Preselected Inductor Value,
No Component Design Required
o
Overcurrent, Soft-Start, and Undervoltage
Lockout Protection
o
Cycle-by-Cycle Current Limiting
o
8-Pin DIP/SO Packages (MAX730A)
_________________Ordering Information
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
MAX730A/MAX738A/MAX744A
5V, Step-Down,
Current-Mode PWM DC-DC Converters
________________________________________________________________
Maxim Integrated Products
1
TOP VIEW
1
2
3
4
8
7
6
5
V+
LX
GND
OUT
CC
SS
REF
MAX730A
MAX738A
MAX744A
DIP
SHDN
Pin Configurations continued on last page.
_________________Pin Configurations
MAX738A
MAX744A
INPUT
6V TO 16V
V+
LX
OUT
CC
GND
SS
REF
SHDN
ON/OFF
33
H
OUTPUT
5V
100
F
68
F
__________Typical Operating Circuit
19-0165; Rev 2; 1/96
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
PART
TEMP. RANGE
PIN-PACKAGE
MAX730A
CPA
0C to +70C
8 Plastic DIP
MAX730ACSA
0C to +70C
8 SO
MAX730AC/D
0C to +70C
Dice*
MAX730AEPA
8 Plastic DIP
MAX730AESA
-40C to +85C
8 SO
-40C to +85C
MAX730AMJA
-55C to +125C
8 CERDIP
MAX730A/MAX738A/MAX744A
5V, Step-Down,
Current-Mode PWM DC-DC Converters
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 3, V+ = 9V for the MAX730A, V+ = 12V for the MAX738A/MAX744A, I
LOAD
= 0mA, T
A
= T
MIN
to T
MAX
,
unless otherwise noted.)
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.
PARAMETER
MAX730A
MIN
TYP
MAX
UNITS
4.75
5.00
5.25
CONDITIONS
Pin Voltages
V+ (MAX730A) ......................................................+12V, -0.3V
V+ (MAX738A/MAX744A) .....................................+18V, -0.3V
LX (MAX730A) .................................(V+ - 12V) to (V+ + 0.3V)
LX (MAX738A/MAX744A) ................(V+ - 21V) to (V+ + 0.3V)
OUT .................................................................................25V
SS, CC,
SHDN .........................................-0.3V to (V+ + 0.3V)
Peak Switch Current (I
LX
) ........................................................2A
Reference Current (I
REF
) ...................................................2.5mA
Continuous Power Dissipation (T
A
= +70C)
8-Pin Plastic DIP (derate 9.09mW/C above +70C)...727mW
8-Pin SO (derate 5.88mW/C above +70C) ...............471mW
16-Pin Wide SO (derate 9.52mW/C above +70C) .....762mW
8-Pin CERDIP (derate 8.00mW/C above +70C) .......640mW
Operating Temperature Ranges:
MAX7_ _AC_ _....................................................0C to +70C
MAX7_ _AE_ _ .................................................-40C to +85C
MAX7_ _AMJA ..............................................-55C to +125C
Junction Temperatures:
MAX7_ _AC_ _/AE_ _...................................................+150C
MAX7_ _AMJA.............................................................+175C
Storage Temperature Range ............................-65C to +160C
Lead Temperature (soldering, 10sec).............................+300C
0mA < I
LOAD
< 450mA,
MAX730AC
0mA < I
LOAD
< 450mA,
MAX730AE
0mA < I
LOAD
< 300mA,
MAX730AM
0mA < I
LOAD
< 450mA,
MAX738AC/AE
0mA < I
LOAD
< 350mA,
MAX738AM
0mA < I
LOAD
< 500mA,
MAX744AC/AE
0mA < I
LOAD
< 375mA,
MAX744AM
MAX738A
MIN
TYP
MAX
4.75
5.00
5.25
4.75
5.00
5.25
MAX744A
MIN
TYP
MAX
4.75
5.00
5.25
4.75
5.00
5.25
Output Voltage
V
V+ = 9.0V
to 16.0V
6.0
16.0
6.0
16.0
5.2
11.0
V
V+ = 5.2V to 11.0V
0.15
V+ = 6.0V to 16.0V
0.15
0.15
%/V
Line Regulation
V+ = 6.0V
to 16.0V
V+ = 6.0V
to 11.0V
V+ = 10.2V to 16.0V,
0mA < I
LOAD
< 750mA
0mA < I
LOAD
< 750mA,
MAX744AC/AE
0mA < I
LOAD
< 600mA,
MAX744AM
Input Voltage
Range
MAX730A/MAX738A/MAX744A
5V, Step-Down,
Current-Mode PWM DC-DC Converters
_______________________________________________________________________________________
3
Note 1:
The standby current typically settles to 25A (over temperature) within 2 seconds; however, to decrease test time, the part
is guaranteed at a 100A maximum value.
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 3, V+ = 9V for the MAX730A, V+ = 12V for the MAX738A/MAX744A, I
LOAD
= 0mA, T
A
= T
MIN
to T
MAX
,
unless otherwise noted.)
PARAMETER
I
LOAD
= 0mA to 300mA
MAX730A
MIN
TYP
MAX
Supply Current
(includes switch
current)
I
LOAD
= 0mA to 750mA
UNITS
V+ = 9.0V, I
LOAD
= 300mA
MAX738A
MIN
TYP
MAX
4.3
mA
MAX744AE
I
LX
= 500mA
6.0
100.0
6.0
100.0
6.0
100.0
A
Standby Current
V
IH
0.0005
LX On Resistance
2.0
2.0
2.0
MAX744AC/AE
0.5
V
IL
MAX744A
MIN
TYP
MAX
0.25
0.25
0.25
V
0.5
0.0005
Shutdown Input
Threshold
%/mA
Shutdown Input
Leakage Current
V+ = 12V, I
LOAD
= 750mA
Load Regulation
0.0005
SHDN = 0V (Note 1)
0.5
1.7
3.0
1.7
3.0
1.7
3.0
159.0 185.0 212.5
MAX744AC/AE
1.2
2.5
V+ = 12V, LX = 0V
MAX744AM
1.0
3.0
1.0
1.0
V+ = 6.0V
to 9.0V
MAX744AC/AE
3.0
1.0
A
Reference Drift
1.0
1.0
MAX744AM
A
3.5
1.5
MAX744AM
V+ = 9.0V
to 12.0V
MAX744AC
4.0
50
50
LX Leakage Current
1.5
87
1.5
CONDITIONS
A
Short-Circuit Current
V+ rising
159.0
216.5
5.7
6.0
5.7
6.0
4.7
5.2
V+ falling
5.0
5.7
V
kHz
Undervoltage
Lockout
90
87
90
%
Efficiency
92
V+ = 6.0V
to 16.0V
V+ = 12V, T
A
= +25C
Reference Voltage
1.15
1.23
1.30
1.15
1.23
1.30
1.15
1.23
1.30
V
50
130
160
190
130
170
210
ppm/C
Oscillator Frequency
7500
7500
7500
Compensation Pin
Impedance
4.5
V+ = 12.0V
to 16.0V
MAX744AM
100
90
80
60
0
200
600
800
1000
OUTPUT CURRENT (mA)
EFFICIENCY (%)
MAX730A
EFFICIENCY vs. OUTPUT CURRENT
70
400
V+ = 5.5V
V+ = 7V
V+ = 9V
V+ = 11V
(NOTES 3, 6)
100
90
80
60
0
200
600
800
1000
OUTPUT CURRENT (mA)
EFFICIENCY (%)
MAX738A
EFFICIENCY vs. OUTPUT CURRENT
70
400
V+ = 6V
V+ = 8V
V+ = 12V
V+ = 16V
(NOTES 3, 6)
2.5
2.0
1.5
0
0
2
6
8
10
QUIESCENT SUPPLY CURRENT (mA)
MAX738A/MAX744A
QUIESCENT SUPPLY CURRENT
vs. SUPPLY VOLTAGE
0.5
4
1.0
12
14
16
UNDERVOLTAGE
LOCKOUT HYSTERESIS
UNDERVOLTAGE
LOCKOUT ENABLED
1000
800
600
0
0
100
300 400 500
PEAK INDUCTOR CURRENT (mA)
MAX738A/MAX744A
PEAK INDUCTOR CURRENT
vs. OUTPUT CURRENT
200
200
400
600 700 800
L1 = 100
H
C4 = 150
F
V+ = 6.6V
V+ = 8.0V TO 16.0V
MAX730A/MAX738A/MAX744A
5V, Step-Down,
Current-Mode PWM DC-DC Converters
4
_______________________________________________________________________________________
__________________________________________Typical Operating Characteristics
(Circuit of Figure 3, T
A
= +25C, unless otherwise noted.)
100
90
80
60
0
200
600
800
1000
OUTPUT CURRENT (mA)
EFFICIENCY (%)
MAX744A
EFFICIENCY vs. OUTPUT CURRENT
70
400
V+ = 6.0V
V+ = 9.0V
V+ = 12.0V
V+ = 16.0V
(NOTE 3)
-60
0
60 80 100
STANDBY SUPPLY CURRENT (
A)
STANDBY SUPPLY CURRENT
vs. TEMPERATURE
16
10
6
2
18
14
12
8
4
0
-40 -20
20 40
120 140 160
V+ = 16V
MAX738A/MAX744A
ONLY
V+ = 9V
V+ = 6V
(NOTES 4, 5)
20
V+ = 12V
MAX738A/MAX744A
ONLY
3.0
2.5
1.5
1.0
0.5
-60
20 40
80
120
TEMPERATURE (C)
QUIESCENT SUPPLY CURRENT (mA)
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
2.0
0
-40 -20 0
60
100
140 160
MAX730A, V+ = 9.0V
MAX738A, V+ = 12.0V
MAX744A, V+ = 12.0V
(NOTES 4, 5)
1400
1000
4
8
10
12
14
SUPPLY VOLTAGE (V)
MAXIMUM OUTPUT CURRENT (mA)
MAXIMUM OUTPUT CURRENT vs.
SUPPLY VOLTAGE
1200
800
6
16
MAX738A
MAX730A
MAX744A
(NOTES 3, 6)
1400
1000
800
4
8
10
12
14
SUPPLY VOLTAGE (V)
MAXIMUM OUTPUT CURRENT (mA)
MAXIMUM OUTPUT CURRENT vs.
SUPPLY VOLTAGE, NO R1
1200
6
16
600
400
200
(NOTES 3, 6)
MAX738A
MAX730A
MAX744A
MAX730A/MAX738A/MAX744A
5V, Step-Down,
Current-Mode PWM DC-DC Converters
_______________________________________________________________________________________
5
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 3, T
A
= +25C, unless otherwise noted.)
4
6
8
10
14
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
OSCILLATOR FREQUENCY vs.
SUPPLY VOLTAGE
12
16
MAX744A
MAX738A
MAX730A
(
NOTE 3)
220
170
160
150
180
190
200
210
210
190
180
-60
20 40
80
120
TEMPERATURE (C)
OSCILLATOR FREQUENCY (kHz)
MAX744A
OSCILLATOR FREQUENCY
vs. TEMPERATURE
200
170
-40 -20 0
60
100
140 160
V+ = 6.0V
V+ = 16.0V
V+ = 9.0V
V+ = 12.0V
(NOTE 4)
200
180
170
160
-60
20 40
80
120
TEMPERATURE (C)
SUPPLY CURRENT (mA)
MAX738A
OSCILLATOR FREQUENCY
vs. TEMPERATURE
190
140
-40 -20 0
60
100
140 160
150
130
120
V+ = 6.0V
V+ = 16.0V
V+ = 12.0V
V+ = 9.0V
(NOTE 4)
-60
20 40
80
120
TEMPERATURE (C)
OSCILLATOR FREQUENCY (kHz)
MAX730A
OSCILLATOR FREQUENCY
vs. TEMPERATURE
-40 -20 0
60
100
140 160
240
200
180
160
220
0
140
V+ = 9.0V
V+ = 7.0V
(NOTE 4)
V+ = 5.5V
V+ = 11.0V
Note 3:
Commercial temperature range external component values in Table 3.
Note 4:
Wide temperature range external component values in Table 3.
Note 5:
Standby and shutdown current includes all external component leakage currents. Capacitor leakage currents dominate at T
A
> +85C,
Sanyo OS-CON capacitors were used.
Note 6:
Operation beyond the specifications listed in the electrical characteristics may exceed the power dissipation ratings of the device.
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