19-0165; Rev 2; 1/96
5V, Step-Down,
Current-Mode PWM DC-DC Converters
__________________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 6µA 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.
________________________________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
6µA 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)
MAX730A/MAX738A/MAX744A
_________________Ordering Information
PART
MAX730ACPA
MAX730ACSA
MAX730AC/D
MAX730AEPA
MAX730AESA
MAX730AMJA
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP
___________________________Applications
Portable Instruments
Cellular Phones and Radios
Personal Communicators
Distributed Power Systems
Computer Peripherals
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
__________Typical Operating Circuit
INPUT
6V TO 16V
V+
33µH
LX
OUTPUT
5V
_________________Pin Configurations
TOP VIEW
68µF
SHDN
1
MAX738A
MAX744A
ON/OFF
SHDN
OUT
8
7
V+
LX
GND
OUT
100µF
REF
2
SS
3
CC
4
MAX730A
MAX738A
MAX744A
DIP
6
5
REF
SS
GND
CC
Pin Configurations continued on last page.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
5V, Step-Down,
Current-Mode PWM DC-DC Converters
MAX730A/MAX738A/MAX744A
ABSOLUTE MAXIMUM RATINGS
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
= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C)...727mW
8-Pin SO (derate 5.88mW/°C above +70°C) ...............471mW
16-Pin Wide SO (derate 9.52mW/°C above +70°C) .....762mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C) .......640mW
Operating Temperature Ranges:
MAX7_ _AC_ _....................................................0°C to +70°C
MAX7_ _AE_ _ .................................................-40°C to +85°C
MAX7_ _AMJA ..............................................-55°C to +125°C
Junction Temperatures:
MAX7_ _AC_ _/AE_ _...................................................+150°C
MAX7_ _AMJA.............................................................+175°C
Storage Temperature Range ............................-65°C to +160°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
(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
CONDITIONS
0mA < I
LOAD
< 450mA,
MAX730AC
V+ = 6.0V
to 11.0V
0mA < I
LOAD
< 450mA,
MAX730AE
0mA < I
LOAD
< 300mA,
MAX730AM
0mA < I
LOAD
< 450mA,
MAX738AC/AE
V+ = 6.0V
to 16.0V
0mA < I
LOAD
< 350mA,
MAX738AM
0mA < I
LOAD
< 500mA,
MAX744AC/AE
0mA < I
LOAD
< 375mA,
MAX744AM
V+ = 10.2V to 16.0V,
0mA < I
LOAD
< 750mA
0mA < I
LOAD
< 750mA,
MAX744AC/AE
4.75 5.00
0mA < I
LOAD
< 600mA,
MAX744AM
5.2
V+ = 5.2V to 11.0V
V+ = 6.0V to 16.0V
0.15
0.15
0.15
11.0
6.0
16.0
6.0
16.0
V
%/V
5.25
4.75 5.00
5.25
4.75 5.00
5.25
MAX730A
MIN TYP MAX
MAX738A
MIN TYP MAX
MAX744A
MIN TYP MAX
UNITS
Output Voltage
4.75 5.00
5.25
4.75 5.00
5.25
V
V+ = 9.0V
to 16.0V
Input Voltage
Range
Line Regulation
2
_______________________________________________________________________________________
5V, Step-Down,
Current-Mode PWM DC-DC Converters
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
Load Regulation
Efficiency
CONDITIONS
I
LOAD
= 0mA to 300mA
I
LOAD
= 0mA to 750mA
V+ = 9.0V, I
LOAD
= 300mA
V+ = 12V, I
LOAD
= 750mA
1.7
V+ = 6.0V
to 9.0V
Supply Current
(includes switch
current)
V+ = 9.0V
to 12.0V
V+ = 12.0V
to 16.0V
Standby Current
Shutdown Input
Threshold
Shutdown Input
Leakage Current
Short-Circuit Current
Undervoltage
Lockout
LX On Resistance
LX Leakage Current
Reference Voltage
Reference Drift
130
Oscillator Frequency
Compensation Pin
Impedance
V+ = 6.0V
to 16.0V
MAX744AC/AE
MAX744AM
7500
7500
V+ rising
V+ falling
I
LX
= 500mA
V+ = 12V, LX = 0V
V+ = 12V, T
A
= +25°C
0.5
1.0
1.15 1.23
50
170
210
130
1.30
0.5
1.0
1.15 1.23
50
160
190
159.0 185.0 212.5
159.0
7500
216.5
Ω
kHz
1.30
1.5
4.7
5.2
MAX744AC/AE
MAX744AM
MAX744AC/AE
MAX744AM
MAX744AC
MAX744AE
MAX744AM
SHDN
= 0V (Note 1)
V
IH
V
IL
2.0
0.25
1.0
1.5
5.7
6.0
5.0
0.5
1.0
1.15 1.23
50
1.30
6.0
100.0
2.0
0.25
1.0
1.5
5.7
6.0
5.7
6.0
100.0
2.0
0.25
1.0
6.0
3.0
92
MAX730A
MIN TYP MAX
0.0005
0.0005
90
87
1.7
3.0
0.0005
90
87
1.7
1.2
3.0
2.5
3.0
3.0
3.5
4.0
4.3
4.5
100.0
µA
V
µA
A
V
Ω
µA
V
ppm/°C
mA
MAX738A
MIN TYP MAX
MAX744A
MIN TYP MAX
UNITS
%/mA
%
MAX730A/MAX738A/MAX744A
Note 1:
The standby current typically settles to 25µA (over temperature) within 2 seconds; however, to decrease test time, the part
is guaranteed at a 100µA maximum value.
_______________________________________________________________________________________
3
5V, Step-Down,
Current-Mode PWM DC-DC Converters
MAX730A/MAX738A/MAX744A
__________________________________________Typical Operating Characteristics
(Circuit of Figure 3, T
A
= +25°C, unless otherwise noted.)
MAX730A
EFFICIENCY vs. OUTPUT CURRENT
100
(NOTES 3, 6)
90
EFFICIENCY (%)
EFFICIENCY (%)
V+ = 5.5V
80
V+ = 7V
V+ = 9V
70
V+ = 11V
90
100
MAX738A
EFFICIENCY vs. OUTPUT CURRENT
100
(NOTES 3, 6)
90
EFFICIENCY (%)
MAX744A
EFFICIENCY vs. OUTPUT CURRENT
(NOTE 3)
V+ = 6V
80
V+ = 8V
V+ = 12V
70
V+ = 16V
V+ = 6.0V
80
V+ = 9.0V
V+ = 12.0V
70
V+ = 16.0V
60
0
200
600
800
OUTPUT CURRENT (mA)
400
1000
60
0
200
600
800
OUTPUT CURRENT (mA)
400
1000
60
0
200
400
600
800
OUTPUT CURRENT (mA)
1000
MAXIMUM OUTPUT CURRENT vs.
SUPPLY VOLTAGE
1400
(NOTES 3, 6)
MAXIMUM OUTPUT CURRENT (mA)
MAXIMUM OUTPUT CURRENT (mA)
1200
1000
800
600
400
200
4
1400
MAXIMUM OUTPUT CURRENT vs.
SUPPLY VOLTAGE, NO R1
3.0
(NOTES 3, 6)
QUIESCENT SUPPLY CURRENT (mA)
2.5
2.0
1.5
1.0
0.5
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
MAX730A, V+ = 9.0V
MAX738A, V+ = 12.0V
MAX744A, V+ = 12.0V
1200
MAX744A
MAX730A
1000
MAX738A
MAX744A
MAX738A
MAX730A
(NOTES 4, 5)
800
4
6
8
10
12
14
16
SUPPLY VOLTAGE (V)
6
8
10
12
14
16
0
-60 -40 -20 0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
MAX738A/MAX744A
QUIESCENT SUPPLY CURRENT
vs. SUPPLY VOLTAGE
2.5
QUIESCENT SUPPLY CURRENT (mA)
1000
MAX738A/MAX744A
PEAK INDUCTOR CURRENT
vs. OUTPUT CURRENT
20
STANDBY SUPPLY CURRENT
vs. TEMPERATURE
(NOTES 4, 5)
PEAK INDUCTOR CURRENT (mA)
2.0
800
STANDBY SUPPLY CURRENT (µA)
18
16
14
12
10
8
6
4
2
0
V+ = 16V
MAX738A/MAX744A
ONLY
V+ = 12V
MAX738A/MAX744A
ONLY
1.5
UNDERVOLTAGE
LOCKOUT HYSTERESIS
UNDERVOLTAGE
LOCKOUT ENABLED
600
1.0
400
V+ = 6.6V
V+ = 8.0V TO 16.0V
0.5
200
L1 = 100µH
C4 = 150µF
V+ = 9V
V+ = 6V
-60 -40 -20
0 20 40 60 80 100 120 140 160
0
0
2
4
6
8
10
12
14
16
0
0
100 200
300 400 500
600 700 800
4
_______________________________________________________________________________________
5V, Step-Down,
Current-Mode PWM DC-DC Converters
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 3, T
A
= +25°C, unless otherwise noted.)
MAX730A/MAX738A/MAX744A
OSCILLATOR FREQUENCY vs.
SUPPLY VOLTAGE
220
(
NOTE 3)
MAX730A
OSCILLATOR FREQUENCY
vs. TEMPERATURE
240
220
200
180
160
140
V+ = 11.0V
(NOTE 4)
210
OSCILLATOR FREQUENCY (kHz)
200
190
MAX744A
180
170
160
150
4
6
8
10
12
SUPPLY VOLTAGE (V)
14
16
OSCILLATOR FREQUENCY (kHz)
MAX730A
V+ = 5.5V
V+ = 7.0V
V+ = 9.0V
MAX738A
0
-60 -40 -20 0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
MAX738A
OSCILLATOR FREQUENCY
vs. TEMPERATURE
200
(NOTE 4)
190
SUPPLY CURRENT (mA)
180
170
160
150
140
130
120
-60 -40 -20 0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
V+ = 12.0V
V+ = 9.0V
V+ = 16.0V
OSCILLATOR FREQUENCY (kHz)
V+ = 6.0V
200
210
MAX744A
OSCILLATOR FREQUENCY
vs. TEMPERATURE
(NOTE 4)
V+ = 6.0V
V+ = 16.0V
190
V+ = 9.0V
180
V+ = 12.0V
170
-60 -40 -20 0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
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 > +85°C,
A
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.
_______________________________________________________________________________________
5
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