19-4505; Rev 4; 7/05
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I
Q
, Step-Down DC-DC Converters
_______________General Description
The MAX639/MAX640/MAX653 step-down switching
regulators provide high efficiency over a wide range of
load currents, delivering up to 225mA. A current-limiting
pulse-frequency-modulated (PFM) control scheme gives
the devices the benefits of pulse-width-modulated
(PWM) converters (high efficiency at heavy loads), while
using only 10µA of supply current (vs. 2mA to 10mA for
PWM converters). The result is high efficiency over a
wide range of loads.
The MAX639/MAX640/MAX653 input range is 4V to
11.5V, and the devices provide lower preset output volt-
ages of 5V, 3.3V, and 3V, respectively. Or, the output
can be user-adjusted to any voltage from 1.3V to the
input voltage.
The MAX639/MAX640/MAX653 have an internal 1A power
MOSFET switch, making them ideal for minimum-compo-
nent, low- and medium-power applications. For increased
output drive capability, use the MAX649/MAX651/MAX652
step-down controllers, which drive an external P-channel
FET to deliver up to 5W.
____________________________Features
♦
High Efficiency for a Wide Range of Load Currents
♦
10µA Quiescent Current
♦
Output Currents Up to 225mA
♦
Preset or Adjustable Output Voltage:
5.0V (MAX639)
3.3V (MAX640)
3.0V (MAX653)
♦
Low-Battery Detection Comparator
♦
Current-Limiting PFM Control Scheme
MAX639/MAX640/MAX653
______________Ordering Information
PART
MAX639CPA
MAX639CSA
MAX639C/D
MAX639EPA
MAX639ESA
MAX639MJA
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
9V Battery to 5V, 3.3V, or 3V Conversion
High-Efficiency Linear Regulator Replacement
Portable Instruments and Handy-Terminals
5V-to-3.3V Converters
Ordering Information continued on last page.
*Contact
factory for dice specifications.
__________Typical Operating Circuit
INPUT
5.5V TO 11.5V
V+
__________________Pin Configuration
TOP VIEW
LX
OUTPUT
5V
225mA
VOUT
1
2
3
4
8
SHDN
MAX639
ON/OFF
LOW-BATTERY
DETECTOR
INPUT
SHDN
LBI
VOUT
LBO
LOW-BATTERY
DETECTOR
OUTPUT
LBO
LBI
GND
MAX639
MAX640
MAX653
7
6
VFB
V+
5
LX
DIP/SO
VFB
GND
________________________________________________________________
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.
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I
Q
, Step-Down DC-DC Converters
MAX639/MAX640/MAX653
ABSOLUTE MAXIMUM RATINGS
V+...........................................................................................12V
LX .........................................................(V+ - 12V) to (V+ + 0.3V)
LBI, LBO, VFB, SHDN, VOUT........................-0.3V to (V+ + 0.3V)
LX Output Current (Note 1) ......................................................1A
LBO Output Current ............................................................10mA
Continuous Power Dissipation (T
A
= +70°C)
Plastic DIP (derate 9.09mW/°C above +70°C) .............727mW
SO (derate 5.88mW/°C above +70°C) ..........................471mW
CERDIP (derate 8.00mW/°C above +70°C) ..................640mW
Operating Temperature Ranges:
MAX639C_ _ .......................................................0°C to +70°C
MAX639E_ _ ....................................................-40°C to +85°C
MAX639MJA ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
Peak inductor current must be limited to 600mA by using an inductor of 100µH or greater.
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+ = 9V for the MAX639, V+ = 5V for the MAX640/MAX653, I
LOAD
= 0mA, T
A
= T
MIN
to T
MAX
, typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
Supply Voltage
Supply Current
Output Voltage (Note 2)
Dropout Voltage
SHDN
= V+, no load
MAX639, V+ = 6.0V to 11.5V, 0mA < I
OUT
< 100mA
MAX640, V+ = 4.0V to 11.5V, 0mA < I
OUT
< 100mA
MAX653, V+ = 4.0V to 11.5V, 0mA < I
OUT
< 100mA
I
OUT
= 100mA, L = 100µH
MAX639
Efficiency
MAX640
MAX653
MAX639
Switch On-Time
MAX640
MAX653
MAX639
Switch Off-Time
MAX640
MAX653
I
OUT
= 100mA, L = 100µH
I
OUT
= 25mA, L = 470µH
I
OUT
= 100mA, L = 100µH
I
OUT
= 25mA, L = 470µH
I
OUT
= 100mA, L = 100µH
I
OUT
= 25mA, L = 470µH
V+ = 9V, V
OUT
= 5V
V+ = 6V, V
OUT
= 3V
V+ = 9V, V
OUT
= 3.3V
V+ = 4V, V
OUT
= 3.3V
V+ = 9V, V
OUT
= 3V
V+ = 4V, V
OUT
= 3V
V+ = 9V, V
OUT
= 5V
V+ = 6V, V
OUT
= 3V
V+ = 9V, V
OUT
= 3.3V
V+ = 4V, V
OUT
= 3.3V
V+ = 9V, V
OUT
= 3V
V+ = 4V, V
OUT
= 3V
10.6
14.2
7.5
60.7
7.1
42.5
9.0
16.6
13.3
13.3
14.6
14.6
4.80
3.17
2.88
CONDITIONS
MIN
4.0
10
5.00
3.30
3.00
0.5
91
94
87
91
85
89
12.5
16.7
8.8
71.4
8.3
50.0
11.7
19.5
15.6
15.6
17.2
17.2
14.4
19.2
10.1
82.1
9.5
57.5
13.5
22.4
17.9
17.9
19.8
19.8
µs
µs
%
TYP
MAX
11.5
20
5.20
3.43
3.12
V
V
UNITS
V
µA
2
_______________________________________________________________________________________
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I
Q
, Step-Down DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 9V for the MAX639, V+ = 5V for the MAX640/MAX653, I
LOAD
= 0mA, T
A
= T
MIN
to T
MAX
, typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
LX Switch On-Resistance
CONDITIONS
V+ = 9V, T
A
= +25°C, MAX639/MAX640/MAX653
V+ = 6V, T
A
= T
MIN
to T
MAX
, MAX639
V+ = 4V, T
A
= T
MIN
to T
MAX
, MAX640/MAX653
LX Switch Leakage
VFB Bias Current
VFB Dual-Mode Trip Point
VFB Threshold
LBI Bias Current
LBI Threshold
LBO Sink Current
LBO Leakage Current
LBO Delay
SHDN
Threshold
SHDN
Pull-Up Current
SHDN
= 0V
MAX6_ _C
MAX6_ _E/M
V
LBI
= 2V
MAX6_ _C
MAX6_ _E/M
V
LBO
= 0.4V
V
LBO
= 11.5V
50mV overdrive
0.80
0.10
MAX639
MAX640/MAX653
1.26
1.24
0.8
0.4
1.26
1.24
V+ = 11.5V, V
LX
= 0V
VFB = 2V
T
A
= +25°C
T
A
= T
MIN
to T
MAX
4.0
50
1.28
1.28
2
1.28
1.28
2.5
1.2
0.001
25
1.15
0.20
2.00
0.40
0.1
1.30
1.32
10
1.30
1.32
0.003
MIN
TYP
0.8
MAX
1.5
2.5
2.8
1.0
30.0
15.0
µA
nA
mV
V
nA
V
mA
µA
µs
V
µA
UNITS
Ω
MAX639/MAX640/MAX653
Note 2:
Output guaranteed by correlation to measurements of device parameters (i.e., switch on-resistance, on-times, off-times, and
output voltage trip points).
__________________________________________Typical Operating Characteristics
(Circuit of Figure 3, internal feedback, L = 100µH, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs.
OUTPUT CURRENT
MAX639-1
EFFICIENCY vs.
OUTPUT CURRENT
L = 470µH
MAX639-2
EFFICIENCY vs.
OUTPUT CURRENT
L = 470µH
V+ = 9V
MAX639-3
100
L = 100µH
V
+
= 9V
100
100
90
EFFICIENCY (%)
EFFICIENCY (%)
90
EFFICIENCY (%)
90
80
MAX639
MAX640
MAX653
80
MAX639, V+ = 6V
MAX640, V+ = 4.3V
MAX653, V+ = 4V
80
MAX639
MAX640
MAX653
70
70
70
60
60
60
50
10µ
100µ
1m
10m
100m
1
OUTPUT CURRENT (A)
50
10µ
100µ
1m
10m
100m
OUTPUT CURRENT (A)
50
10µ
100µ
1m
10m
100m
OUTPUT CURRENT (A)
_______________________________________________________________________________________
3
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I
Q
, Step-Down DC-DC Converters
MAX639/MAX640/MAX653
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 3, internal feedback, L = 100µH, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs.
INPUT VOLTAGE
MAX639-05
MAX639-4
EFFICIENCY vs.
OUTPUT CURRENT
100
100
L = 100µH
EFFICIENCY vs.
INPUT VOLTAGE
L = 470µH
I
OUT
= 25mA
95
EFFICIENCY (%)
MAX639
MAX639-06
I
OUT
= 100mA
95
MAX639
100
90
EFFICIENCY (%)
EFFICIENCY (%)
80
70
MAX639, V+ = 6V
MAX640, V+ = 4.3V
MAX653, V+ = 4V
90
MAX640
90
MAX640
85
MAX653
85
60
MAX653
50
10µ
100µ
1m
10m
100m
1
OUTPUT CURRENT (A)
80
3
4
5
6
7
8
9
10
11
12
V+ (V)
80
3
4
5
6
7
8
9
10
11
12
V+ (V)
MAXIMUM OUTPUT CURRENT vs.
INPUT VOLTAGE
MAX639-07
MAXIMUM OUTPUT CURRENT vs.
INPUT VOLTAGE
MAX639-08
MAX639
OUTPUT VOLTAGE RIPPLE vs.
INPUT VOLTAGE
I
OUT
= 25mA
OUTPUT VOLTAGE RIPPLE (mV)
125
100
75
50
25
L = 470µH
0
L = 100µH
MAX639-09
250
L = 100µH
MAXIMUM OUTPUT CURRENT (mA)
75
L = 470µH
MAXIMUM OUTPUT CURRENT (mA)
65
MAX639
55
MAX640
150
200
MAX640
MAX653
45
MAX653
150
MAX639
100
3
4
5
6
7
8
9
10
11
12
V+ (V)
L = 220µH
35
25
3
4
5
6
7
8
9
10
11
12
5
6
7
8
9
10
11
12
V+ (V)
INPUT VOLTAGE (V)
MAX640
OUTPUT VOLTAGE RIPPLE vs.
INPUT VOLTAGE
MAX639-10
MAX653
OUTPUT VOLTAGE RIPPLE vs.
INPUT VOLTAGE
I
LOAD
= 25mA
OUTPUT VOLTAGE RIPPLE (mV)
125
100
75
50
25
L = 470µH
0
L = 220µH
L = 100µH
MAX639-11
150
I
OUT
= 25mA
OUTPUT VOLTAGE RIPPLE (mV)
125
L = 100µH
100
75
50
25
0
3
4
5
6
7
8
9
10
11
L = 220µH
L = 470µH
150
12
3
4
5
6
7
8
9
10
11
12
V+ (V)
V+ (V)
4
_______________________________________________________________________________________
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I
Q
, Step-Down DC-DC Converters
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 3, internal feedback, L = 100µH, T
A
= +25°C, unless otherwise noted.)
MAX639
START-UP TIME vs.
OUTPUT CURRENT
MAX639-12
MAX639/MAX640/MAX653
MAX640/MAX653
START-UP TIME vs.
OUTPUT CURRENT
MEASURED FROM THE RISING EDGE OF V+
OR SHDN TO (V
OUT
= 3.3V)(MAX640) OR
(V
OUT
= 3.0V)(MAX653). THE START-UP
TIME DIFFERENCE BETWEEN THE
MAX640 AND THE MAX653
IS NEGLIGIBLE.
V+ = 5.0V
4
V+ = 9.0V
MAX639-13
MAX639
START-UP TIME vs.
OUTPUT CURRENT
MEASURED FROM THE RISING EDGE
OF V+ OR SHDN TO (V
OUT
= 5.0V)
L = 470µH.
START-UP TIME (ms)
30
V+ = 5.5V
20
V+ = 9.0V
MAX639-14
12
10
START-UP TIME (ms)
8
6
4
2
0
0
V+ = 11.5V
V+ = 9.0V
MEASURED FROM THE RISING EDGE
OF V+ OR SHDN TO (V
OUT
= 5V).
V+ = 5.5V
10
40
8
START-UP TIME (ms)
6
10
V+ = 11.5V
2
0
L = 100µH
0
V+ = 11.5V
0
0
5
10
15
20
25
30
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
10 20 30 40 50 60 70 80 90 100
MAX640/MAX653
START-UP TIME vs.
OUTPUT CURRENT
MAX639-15
NO-LOAD SUPPLY CURRENT vs.
INPUT VOLTAGE
MAX639-16
40
70
NO-LOAD SUPPLY CURRENT (µA)
60
MAX639, V
OUT
= 5V
50
40
30
20
10
0
START-UP TIME (ms)
30
MEASURED FROM THE RISING EDGE OF
V+ OR SHDN TO (V
OUT
= 3.3V)(MAX640)
OR (V
OUT
= 3.0V)(MAX653). THE
START-UP TIME DIFFERENCE BETWEEN
THE MAX640 AND THE MAX653 IS
NEGLIGIBLE.
L = 470µH
V+ = 5.0V
20
MAX653, V
OUT
= 3V
10
V+ = 11.5V
0
0
5
10
15
20
V+ = 9.0V
25
30
0 1
2
3 4
5
6
7 8
9 10 11 12
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
_______________________________________________________________________________________
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