19-0305; Rev 3; 3/09
IT
TION K
VALUA
E
BLE
AVAILA
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
____________________________Features
♦
More than 90% Efficiency (10mA to 1.5A Loads)
♦
More than 12.5W Output Power
♦
Less than 0.3V Dropout Voltage at 500mA
♦
♦
♦
♦
100µA Max Quiescent Supply Current
5µA Max Shutdown Supply Current
16V Max Input Voltage
5V (MAX1649), 3.3V (MAX1651), or Adjustable
Output Voltage
♦
Current-Limited Control Scheme
♦
Up to 300kHz Switching Frequency
♦
Up to 96.5% Duty Cycle
_______________General Description
The MAX1649/MAX1651 BiCMOS, step-down, DC-DC
switching controllers provide high efficiency over loads
ranging from 1mA to more than 2.5A. A unique, current-
limited pulse-frequency-modulated (PFM) control scheme
gives these devices the benefits of pulse-width-modula-
tion (PWM) converters (high efficiency at heavy loads),
while using only 100µA of supply current (vs. 2mA to
10mA for PWM converters). Dropout performance down
to 300mV is provided by a high switch duty cycle (96.5%)
and a low current-sense threshold (110mV).
A high switching frequency (up to 300kHz) allows these
devices to use miniature external components.
The MAX1649/MAX1651 have dropout voltages less
than 0.3V at 500mA and accept input voltages up to
16V. Output voltages are preset at 5V (MAX1649), or
3.3V (MAX1651). They can also be adjusted to any
voltage from 1.5V to the input voltage by using two
resistors.
These step-down controllers drive external P-channel
MOSFETs at loads greater than 12.5W. If less power is
required, use the MAX639/MAX640/MAX653 step-down
converters with on-chip FETs, which allow up to a
225mA load current.
MAX1649/MAX1651
______________Ordering Information
PART
MAX1649CPA
MAX1649CSA
MAX1649C/D
MAX1649EPA
MAX1649ESA
MAX1651CPA
MAX1651CSA
MAX1651C/D
MAX1651EPA
MAX1651ESA
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
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
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
________________________Applications
PDAs
High-Efficiency Step-Down Regulation
5V-to-3.3V Green PC Applications
Battery-Powered Applications
*Dice are tested at T
A
= +25°C.
__________Typical Operating Circuit
INPUT
3.6V TO 16V
__________________Pin Configuration
TOP VIEW
V+
OUT
1
2
8
7
GND
EXT
CS
V+
MAX1651
ON/OFF
SHDN
CS
EXT
P
OUTPUT
3.3V
FB
SHDN
3
REF
4
MAX1649
MAX1651
6
5
REF
FB
GND
OUT
DIP/SO
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
MAX1649/MAX1651
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V+ to GND.......................................-0.3V, +17V
REF, SHDN, FB, CS, EXT, OUT .......................-0.3V, (V+ + 0.3V)
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
Operating Temperature Ranges
MAX1649C_A, MAX1651C_A ..............................0°C to +70°C
MAX1649E_A, MAX1651E_A ............................-40°C to +85°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
(V+ = 5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
V+ Input Voltage Range
Supply Current
SYMBOL
V+
I+
V
OUT
< V+
V+ = 16V, SHDN
≤
0.4V (operating, switch off)
V+ = 16V, SHDN
≥
1.6V (shutdown)
V+ = 10V, SHDN
≥
1.6V (shutdown)
FB Trip Point
FB Input Current
Output Voltage
Reference Voltage
REF Load Regulation
REF Line Regulation
I
FB
V
OUT
V
REF
MAX1649C, MAX1651C
MAX1649E, MAX1651E
MAX1649C, MAX1651C
MAX1649E, MAX1651E
MAX1649, V+ = 5.5V to 16V
MAX1651, V+ = 3.6V to 16V
MAX1649C, MAX1651C, I
REF
= 0μA
MAX1649E, MAX1651E, I
REF
= 0μA
0µA
≤
I
REF
≤
100µA, sourcing only
3V
≤
V+
≤
16V
Circuit of
Figure 1
MAX1649, 5.5V
≤
V+
≤
16V,
I
LOAD
= 1A
MAX1651, 3.6V
≤
V+
≤
16V,
I
LOAD
= 1A
MAX1649, 0A
≤
I
LOAD
≤
1.5A,
V
IN
= 10V
MAX1651, 0A
≤
I
LOAD
≤
1.5A,
V
IN
= 5V
MAX1649, V+ = 10V,
I
LOAD
= 1A
MAX1651, V+ = 5V,
I
LOAD
= 1A
1.6
0.4
4.80
3.17
1.470
1.4625
5.0
3.3
1.5
1.5
4
40
2.6
mV/V
1.7
-47
mV/A
-45
90
%
90
1
µA
V
V
1.470
1.4625
CONDITIONS
MIN
3.0
78
2
1
1.5
1.5
5
1.530
1.5375
±50
±70
5.20
3.43
1.530
1.5375
10
100
V
nA
V
V
mV
µV/V
TYP
MAX
16
100
µA
UNITS
V
Output Voltage
Line Regulation
Output Voltage
Load Regulation
Circuit of
Figure 1
Efficiency
Circuit of
Figure 1
SHDN Input Current
SHDN Input Voltage High
SHDN Input Voltage Low
V
IH
V
IL
V+ = 16V, SHDN = 0V or V+
3V
≤
V+
≤
16V
3V
≤
V+
≤
16V
2
_______________________________________________________________________________________
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Current-Limit Trip Level
(V+ to CS)
CS Input Current
Switch Maximum On-Time t
ON
(max)
Switch Minimum Off-Time t
OFF
(min)
EXT Rise Time
EXT Fall Time
Maximum Duty Cycle
SYMBOL
V
CS
3V
≤
V+
≤
16V
3V
≤
V+
≤
16V
V+ = 12V
V+ = 12V
C
EXT
= 0.001µF, V+ = 12V
C
EXT
= 0.001µF, V+ = 12V
t
ON
x 100%
t
ON
+ t
OFF
95
24
0.8
32
1.1
25
25
96.5
CONDITIONS
MIN
80
TYP
110
MAX
140
±1
40
1.8
UNITS
mV
µA
µs
µs
ns
ns
%
MAX1649/MAX1651
__________________________________________Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX1649-TOC06
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX1649-TOC05
EXT RISE AND FALL TIMES
vs. TEMPERATURE (1nF)
55
50
t
RISE
& t
FALL
(ns)
45
40
35
30
25
V+ = 15V, t
RISE
V+ = 15V, t
FALL
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
C
EXT
= 1nF
MAX1649/51-01
80
78
76
I+ (μA)
V+ = 10V
V+ = 16V
4.0
3.5
3.0
V+ = 16V
2.5
I+ (μA)
2.0
1.5
V+ = 8V
1.0
60
V+ = 5V, t
RISE
74
72
70
V+ = 5V, t
FALL
V+ = 4V
68
66
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (°C)
0.5
V+ = 4V
0
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (°C)
20
15
EXT RISE AND FALL TIMES
vs. TEMPERATURE (5nF)
MAX1649/51-02
EFFICIENCY
vs. LOAD CURRENT (V
OUT
= 5V)
V
OUT
= 5V
CIRCUIT OF
FIGURE 1
MAX1649/51-A1
220
200
t
RISE
& t
FALL
(ns)
180
160
140
120
100
80
60
40
C
EXT
= 5nF
V+ = 5V, t
RISE
90
EFFICIENCY (%)
80
70
60
50
90
EFFICIENCY (%)
80
70
60
50
40
0.1
V
OUT
= 3.3V
CIRCUIT OF
FIGURE 1
V+ = 5V, t
FALL
V+ = 15V, t
RISE
TOP TO
BOTTOM:
TOP TO
BOTTOM:
V+ = 15V, t
FALL
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
V
IN
= 6V
V
IN
= 8V
V
IN
= 10V
V
IN
= 12V
V
IN
= 15V
0.1
1
100
1k
10
LOAD CURRENT (mA)
10k
V
IN
= 4.3V
V
IN
= 5V
V
IN
= 8V
V
IN
= 10V
V
IN
= 12V
V
IN
= 15V
1
100
1k
10
LOAD CURRENT (mA)
10k
40
_______________________________________________________________________________________
3
MAX1649/51-A2
240
100
EFFICIENCY
vs. LOAD CURRENT (V
OUT
= 3.3V)
100
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
MAX1649/MAX1651
____________________________Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
SWITCH ON-TIME
vs. TEMPERATURE
MAX1649/51-03
SWITCH OFF-TIME
vs. TEMPERATURE
MAX1649/51-04
MAXIMUM DUTY CYCLE
vs. TEMPERATURE
MAX1649/51-05
34.0
33.5
33.0
1.5
1.4
1.3
100
99
DUTY CYCLE (%)
98
97
96
95
94
93
1.2
t
OFF
(μs)
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
t
ON
(μs)
32.5
32.0
31.5
31.0
30.5
30.0
1.1
1.0
0.9
0.8
0.7
0.6
0.5
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
CS TRIP LEVEL
vs. TEMPERATURE
MAX1649/51-06
DROPOUT VOLTAGE
vs. LOAD CURRENT
CIRCUIT OF
FIGURE 1
MAX1649/51-A3
120
600
500
DROPOUT VOLTAGE (mV)
400
300
115
CS TRIP LEVEL (mV)
V
OUT
= 4.80V
110
105
V
OUT
= 3.17V
200
100
0
100
95
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
REFERENCE OUTPUT RESISTANCE
vs. TEMPERATURE
REFERENCE OUTPUT RESISTANCE (Ω)
MAX1649-TOC07
REFERENCE OUTPUT VOLTAGE
vs. TEMPERATURE
MAX1649-TOC01
250
1.506
REFERENCE OUTPUT VOLTAGE (V)
1.504
1.502
1.500
1.498
1.496
1.494
1.492
200
I
REF
= 10μA
I
REF
= 10μA
150
I
REF
= 50μA
100
50
I
REF
= 100μA
0
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (°C)
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (°C)
4
_______________________________________________________________________________________
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
____________________________Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
MAX1649
LINE-TRANSIENT RESPONSE
MAX1649
LOAD-TRANSIENT RESPONSE
MAX1649/MAX1651
A
A
16V
B
1.6A
B
6V
0A
5ms/div
CIRCUIT OF FIGURE 1, I
LOAD
= 1A
A: V
OUT
= 5V, 100mV/div, AC-COUPLED
B: V+ = 6V TO 16V, 5V/div
200μs/div
CIRCUIT OF FIGURE 1, V+ = 10V
A: V
OUT
= 5V, 100mV/div, AC-COUPLED
B: I
LOAD
= 30mA TO 1.6A, 1A/div
MAX1649
SHDN RESPONSE TIME
5V
OUTPUT
0V
4V
SHDN
INPUT
0V
1ms/div
CIRCUIT OF FIGURE 1, V+ = 10V, I
LOAD
= 1A
_______________________________________________________________________________________
5
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