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19-0263; Rev 1; 7/95
12V or Adjustable, High-Efficiency,
Low I Q , Step-Up DC-DC Controller
_______________General Description
The MAX1771 step-up switching controller provides
90% efficiency over a 30mA to 2A load. A unique cur-
rent-limited pulse-frequency-modulation (PFM) control
scheme gives this device the benefits of pulse-width-
modulation (PWM) converters (high efficiency at heavy
loads), while using less than 110µA of supply current (vs.
2mA to 10mA for PWM converters).
This controller uses miniature external components. Its
high switching frequency (up to 300kHz) allows sur-
face-mount magnetics of 5mm height and 9mm diame-
ter. It accepts input voltages from 2V to 16.5V. The
output voltage is preset at 12V, or can be adjusted
using two resistors.
The MAX1771 optimizes efficiency at low input voltages
and reduces noise by using a single 100mV current-limit
threshold under all load conditions. A family of similar
devices, the MAX770–MAX773, trades some full-load
efficiency for greater current-limit accuracy; they provide
a 200mV current limit at full load, and switch to 100mV
for light loads.
The MAX1771 drives an external N-channel MOSFET
switch, allowing it to power loads up to 24W. If less power
is required, use the MAX756/MAX757 or MAX761/MAX762
step-up switching regulators with on-board MOSFETs.
An evaluation kit is available. Order the MAX1771EVKIT-SO.
________________________Applications
Positive LCD-Bias Generators
Flash Memory Programmers
High-Power RF Power-Amplifier Supply
Palmtops/Hand-Held Terminals
Battery-Powered Applications
Portable Communicators
____________________________Features
©
90% Efficiency for 30mA to 2A Load Currents
©
Up to 24W Output Power
©
110µA Max Supply Current
©
5µA Max Shutdown Current
©
2V to 16.5V Input Range
©
Preset 12V or Adjustable Output Voltage
©
Current-Limited PFM Control Scheme
©
Up to 300kHz Switching Frequency
©
Evaluation Kit Available
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1771CPA
0°C to +70°C
8 Plastic DIP
MAX1771CSA
0°C to +70°C
8 SO
MAX1771C/D
0°C to +70°C
Dice*
MAX1771EPA
-40°C to +85°C
8 Plastic DIP
MAX1771ESA
-40°C to +85°C
8 SO
MAX1771MJA
-55°C to +125°C
8 CERDIP**
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883B.
__________________Pin Configuration
__________Typical Operating Circuit
TOP VIEW
INPUT
2V TO V OUT
OUTPUT
12V
EXT
1
2
3
4
8
7
6
5
CS
GND
AGND
REF
MAX1771
EXT
N
V+
MAX1771
ON/OFF
SHDN
CS
FB
SHDN
REF
FB AGND GND V+
DIP/SO
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
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12V or Adjustable, High-Efficiency,
Low I Q , Step-Up DC-DC Controller
Operating Temperature Ranges
MAX1771C_ A .....................................................0°C to +70°C
MAX1771E_ A ..................................................-40°C to +85°C
MAX1771MJA ................................................-55°C to +125°C
Junction Temperatures
MAX1771C_ A/E_ A.......................................................+150°C
MAX1771MJA ..............................................................+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
(V+ = 5V, I LOAD = 0mA, T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1771 (internal feedback resistors)
2.0
12.5
Input Voltage Range
MAX1771C/E (external resistors)
3.0
16.5
V
MAX1771MJA (external resistors)
3.1
16.5
Minimum Start-Up Voltage
1.8
2.0
V
Supply Current
V+ = 16.5V, SHDN = 0V (normal operation)
85
110
m
A
V+ = 10.0V, SHDN ³ 1.6V (shutdown)
V+ = 16.5V, SHDN
2
5
m
A
Standby Current
³
1.6V (shutdown)
4
Output Voltage (Note 1)
V+ = 2.0V to 12.0V, over full load range,
Circuit of Figure 2a
11.52
12.0
12.48
V
Output Voltage Line Regulation
(Note 2)
V+ = 5V to 7V, V OUT = 12V
I LOAD = 700mA, Circuit of Figure 2a
5
mV/V
Output Voltage Load Regulation
(Note 2)
V+ = 6V, V OUT = 12V, I LOAD = 0mA to
500mA, Circuit of Figure 2a
20
mV/A
Maximum Switch On-Time
t ON (max)
12
16
20
m s
Minimum Switch Off-Time
t OFF (min)
1.8
2.3
2.8
m s
Efficiency
V+ = 5V, V OUT = 12V, I LOAD = 500mA,
Circuit of Figure 2a
92
%
MAX1771C
1.4700
1.5
1.5300
Reference Voltage
V REF
I REF = 0 m A
MAX1771E
1.4625
1.5
1.5375
V
MAX1771M
1.4550
1.5
1.5450
MAX1771C/E
4
10
REF Load Regulation
0µA ²
I REF ²
100µA
mV
MAX1771M
4
15
REF Line Regulation
3V
²
V+
²
16.5V
40
100
µV/V
MAX1771C
1.4700
1.5
1.5300
FB Trip Point Voltage
V FB
MAX1771E
1.4625
1.5
1.5375
V
MAX1771M
1.4550
1.5
1.5450
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
Supply Voltage
V+ to GND ...............................................................-0.3V, 17V
EXT, CS, REF, SHDN, FB to GND ...................-0.3V, (V+ + 0.3V)
GND to AGND.............................................................0.1V, -0.1V
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
11021223.005.png
12V or Adjustable, High-Efficiency,
Low I Q , Step-Up DC-DC Controller
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V, I LOAD = 0mA, T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C.)
PARAMETERS
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1771C
±20
FB Input Current
I FB
MAX1771E
±40
nA
MAX1771M
±60
SHDN Input High Voltage
V IH
V+ = 2.0V to 16.5V
1.6
V
SHDN Input Low Voltage
V IL
V+ = 2.0V to 16.5V
0.4
V
SHDN Input Current
V+ = 16.5V, SHDN = 0V or V+
±1
m
A
MAX1771C/E
MAX1771M
85
100
115
Current-Limit Trip Level
V CS
V+ = 5V to 16V
mV
75
100
125
CS Input Current
0.01
±1
m A
EXT Rise Time
V+ = 5V, 1nF from EXT to ground
55
ns
EXT Fall Time
V+ = 5V, 1nF from EXT to ground
55
ns
Note 1: Output voltage guaranteed using preset voltages. See Figures 4a–4d for output current capability versus input voltage.
Note 2: Output voltage line and load regulation depend on external circuit components.
__________________________________________Typical Operating Characteristics
(T A = +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(BOOTSTRAPED MODE)
EFFICIENCY vs. LOAD CURRENT
(NON-BOOTSTRAPED MODE)
LOAD CURRENT vs.
MINIMUM START-UP INPUT VOLTAGE
100
100
700
95
V IN = 10V
95
600
V OUT = 12V, CIRCUIT OF FIGURE 2a
V IN =10V
EXTERNAL FET THRESHOLD
LIMITS FULL-LOAD START-UP
BELOW 3.5V
90
V IN = 8V
90
500
V IN = 8V
85
85
400
V IN = 3V
80
80
V IN = 5V
300
75
70
V IN = 5V
75
70
200
V OUT = 12V
CIRCUIT OF
FIGURE 2a
V OUT = 12V
CIRCUIT OF
FIGURE 2b
65
65
100
60
60
0
2.00
1
10
100
1000
10,000
1
10
100
1000
10,000
2.25 2.50 2.75 3.00 3.25 3.50
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MINIMUM START-UP INPUT VOLTAGE (V)
_______________________________________________________________________________________ 3
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12V or Adjustable, High-Efficiency,
Low I Q , Step-Up DC-DC Controller
____________________________Typical Operating Characteristics (continued)
(T A = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
EXT RISE/FALL TIME vs. SUPPLY VOLTAGE
4
V OUT = 12V, V IN = 5V
CIRCUIT OF FIGURE 2a
BOOTSTRAPPED MODE
0.8
250
V OUT = 12V
3
200
C EXT = 1000pF
0.6
BOOTSTRAPPED
CIRCUIT OF
FIGURE 2a
C EXT = 2200pF
C EXT = 446pF
ENTIRE
CIRCUIT
150
C EXT = 100pF
2
0.4
100
1
SCHOTTKY DIODE
LEAKAGE EXCLUDED
0.2
50
0
0
NON-BOOTSTRAPPED
CIRCUIT OF FIGURE 2b
0
-75 -50 -25 0 25 50 75 100 125
2
4
6
8
10
12
2
4
6
8
10
12
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
REFERENCE OUTPUT RESISTANCE vs.
TEMPERATURE
REFERENCE vs. TEMPERATURE
MAXIMUM SWITCH ON-TIME vs.
TEMPERATURE
250
1.506
16.5
1.504
200
10µA
1.502
150
1.500
16.0
100
1.498
50µA
1.496
100µA
50
1.494
0
1.492
15.5
-60
-40
-20
0
20
40
60
80
100
120
140
-60
-40
-20
0
20
40
60
80
100
120
140
-60 -30
0
30
60
90 120 150
TEMPERATURE ( ° C)
TEMPERATURE ( ° C)
TEMPERATURE (°C)
SHUTDOWN CURRENT vs. TEMPERATURE
MINIMUM SWITCH OFF-TIME vs.
TEMPERATURE
MAXIMUM SWITCH ON-TIME/
MINIMUM SWITCH OFF-TIME RATIO
vs. TEMPERATURE
4.0
2.30
8.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
7.5
V+ = 15V
2.25
7.0
V+ = 8V
6.5
V+ = 4V
2.20
6.0
-60
-40
-20
0
20
40
60
80
100
120
140
-60 -30
0
30
60
90 120 150
-60 -30
0
30
60
90 120 150
TEMPERATURE ( ° C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4 _______________________________________________________________________________________
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12V or Adjustable, High-Efficiency,
Low I Q , Step-Up DC-DC Controller
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, T A = +25°C, unless otherwise noted.)
HEAVY-LOAD SWITCHING WAVEFORMS
MEDIUM-LOAD SWITCHING WAVEFORMS
V OUT
A
V OUT
A
0V
I LIM
0V
I LIM
B
B
0A
0A
C
C
2µs/div
V IN = 5V, I OUT = 900mA, V OUT = 12V
A: EXT VOLTAGE, 10V/div
B: INDUCTOR CURRENT, 1A/div
C: V OUT RIPPLE, 50mV/div, AC-COUPLED
10µs/div
V IN = 5V, I OUT = 500mA, V OUT = 12V
A: EXT VOLTAGE, 10V/div
B: INDUCTOR CURRENT, 1A/div
C: V OUT RIPPLE, 50mV/div, AC-COUPLED
LINE-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
A
7V
500mA
5V
A
0A
0V
B
B
5ms/div
5ms/div
I OUT = 700mA, V OUT = 12V
A: V IN , 5V to 7V, 2V/div
B: V OUT RIPPLE, 100mV/div, AC-COUPLED
V IN = 6V, V OUT = 12V
A: LOAD CURRENT, 0mA to 500mA, 500mA/div
B: V OUT RIPPLE, 100mV/div, AC-COUPLED
_______________________________________________________________________________________ 5
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