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19-0186; Rev 2; 7/96
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Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_______________General Description
The MAX777L/MAX778L/MAX779L are pulse-skipping DC-DC
converters that step up from low-voltage inputs (1V guaran-
teed). They require only three external components—an induc-
tor (typically 22µH) and two capacitors. The MAX777L delivers
a 5V output, the MAX778L generates pin-selectable voltages of
3.0V or 3.3V, and the MAX779L output can be adjusted from
2.5V to 6V through an external resistive divider.
The devices include an Active RectifierTM that eliminates the
need for an external catch diode, and permits regulation even
when the input is greater than the output. Also, unlike those in
other step-up converters, the MAX777L/MAX778L/MAX779L’s
Active RectifierTM turns off in the shutdown mode, disconnect-
ing the output from the source. This eliminates the current drain
associated with conventional step-up converters when off or in
shutdown.
High-frequency operation (up to 150kHz) allows the use of
small, surface-mount inductors with values of 10µH or less.
Supply current is 190µA under no load and only 20µA in stand-
by mode; supply voltage can range from 1V to 4.5V (1 to 3
cells). With a 2V input, the devices typically deliver 200mA at
5V, or 300mA at 3V.
For fully specified devices designed for step-up/step-down
applications (where the input can be above or below the out-
put), refer to the MAX877L/MAX878L/MAX879L data sheet.
________________________Applications
Single Battery-Cell (1V), Step-Up Voltage Conversion
Efficient, High-Power Step-Up Regulation from
Low Input Voltages
Pagers
Portable Instruments & Hand-Held Terminals
Notebook and Palmtop Computers
__________Typical Operating Circuit
____________________________Features
o 1V to 4.5V Input Guarantees Start-Up Under Load
o Up to 210mA Output
o Load Fully Disconnected in Shutdown
o 82% Efficiency
o Output in Regulation with Input Voltage above
Output Voltage
o Internal 1A Power Switch and Active Rectifier
o Adjustable Current Limit Allows Low-Cost
Inductors
o 190µA No Load Supply Current
o 20µA Shutdown Supply Current
o 3V/3.3V (MAX778L), 5V (MAX777L), and
Adjustable (MAX779L) Output Voltage
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX777LCPA
0°C to +70°C
8 Plastic DIP
MAX777LCSA
0°C to +70°C
8 SO
MAX777LC/D
0°C to +70°C
Dice*
MAX777LEPA
-40°C to +85°C
8 Plastic DIP
MAX777LESA
-40°C to +85°C
8 SO
MAX777LMJA -55°C to +125°C
8 CERDIP**
Ordering Information continued at end of data sheet.
* Dice are specified at TA = +25°C, DC parameters only.
**Contact factory for availability and processing to MIL-STD-883.
__________________Pin Configuration
INPUT
1V TO 4.5V
TOP VIEW
22µF
ON/OFF
2
IN
1 ILIM MAX777L
5
LX
7
SHDN
6
OUT
PGND
4
AGND
3
22µH
OUTPUT
5V
100µF
ILIM 1
IN 2
AGND 3
PGND 4
MAX777L
MAX778L
MAX779L
8 N.C. (MAX777L)*
7 SHDN
6 OUT
5 LX
DIP/SO
* SEL FOR MAX778L, FB FOR MAX779L.
Active Rectifier is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
www.DataSheet4U.com
www.DataSheet4U.com

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Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (IN to PGND).......................................0V to 4.5V
Output Short-Circuit Duration to PGND, AGND (Note 1)....30sec
Voltage Applied to:
LX (switch off) .......................................................-0.3V to 4.5V
(switch on) ....................................30sec short to IN or OUT
OUT, SHDN ...........................................................-0.3V to +7V
FB ...........................................................-0.3V to (OUT + 0.3V)
AGND to PGND ........................................................-0.3V, +0.3V
Reverse Battery Current....................................................900mA
Continuous Power Dissipation (TA = +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:
MAX77_LC_A .......................................................0°C to +70°C
MAX77_LE_A ....................................................-40°C to +85°C
MAX77_LMJA .................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1: The output may be shorted to ground if the package power dissipation is not exceeded.
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
(VIN = +2.5V, ILOAD = 0mA, L = 22µH, COUT = 100µF, SHDN and ILIM connected to IN, AGND connected to PGND, TA = TMIN to TMAX,
typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Minimum Start-Up Voltage ILOAD < 10mA, TA = +25°C (Note 2)
1V
Maximum Operating Voltage (Notes 2, 3)
4.5 V
Output Voltage
MAX777L/MAX779L
(set to 5V)
(Note 6)
Output Voltage
MAX778L
(Note 6)
Output Voltage Range
(MAX779L)
MAX777LC/
MAX779LC
MAX777LE/
MAX779LE
MAX777LM/
MAX779LM
MAX778LC
SEL = 0V MAX778LE
MAX778LM
MAX778LC
SEL = OPEN MAX778LE
MAX778LM
(Note 4)
ILOAD 30mA, 1.1V VIN 4.5V or
ILOAD 140mA, 1.8V VIN 4.5V
ILOAD 30mA, 1.2V VIN 4.5V or
ILOAD 130mA, 1.8V VIN 4.5V
ILOAD 25mA, 1.25V VIN 4.5V or
ILOAD 120mA, 1.8V VIN 4.5V
ILOAD 50mA, 1.1V VIN 3.3V or
ILOAD 210mA, 1.8V VIN 3.3V
ILOAD 50mA, 1.2V VIN 3.3V or
ILOAD 200mA, 1.8V VIN 3.3V
ILOAD 50mA, 1.25V VIN 3.3V or
ILOAD 180mA, 1.8V VIN 3.3V
ILOAD 50mA, 1.1V VIN 3V or
ILOAD 210mA, 1.8V VIN 3V
ILOAD 50mA, 1.2V VIN 3V or
ILOAD 200mA, 1.8V VIN 3V
ILOAD 40mA, 1.25V VIN 3V or
ILOAD 180mA, 1.8V VIN 3V
4.80 5.00 5.20 V
3.17 3.30 3.43
V
2.88 3.00 3.12
2.5 6.0 V
Efficiency
ILOAD = 100mA
82 %
No-Load Supply Current ILOAD = 0mA (switch off)
190 310 µA
Shutdown Supply Current SHDN = 0V MAX77_LC, MAX77_LE
MAX77_LM
20 30
µA
20 35
SHDN Input Current
0V < SHDN < VIN
VIN < SHDN < 5V
15 100 nA
12 40 µA
2 _______________________________________________________________________________________

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Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +2.5V, ILOAD = 0mA, L = 22µH, COUT = 100µF, SHDN and ILIM connected to IN, AGND connected to PGND, TA = TMIN to TMAX,
typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
SHDN Threshold
SHDN Enable Delay
Current Limit
Current-Limit Temperature
Coefficient
Switch Saturation Voltage
Maximum Switch On Time
Minimum Switch Off Time
Rectifier Forward Voltage Drop
Error-Comparator Trip Point
FB Pin Bias Current
Switch Off Leakage Current
Rectifier Off Leakage Current
VIN = 1V to 4.5V
VIN = 2.5V
CONDITIONS
ISW = 400mA
ISW = 600mA
ISW = 1000mA
VIN = 2.5V
VIN = 1.8V
VIN = 1V
MAX777L, MAX779L
MAX778
ISW = 400mA
ISW = 600mA
ISW = 1000mA
MAX779L, over operating input voltage (Note 5)
MAX779L, VFB = 0.3V
MIN TYP MAX
VIN/2 + 0.25
1.20
1.6
150
1.0
UNITS
V
µs
A
-0.3 %/°C
197.5
0.275
0.33
0.50
4.0
5.9
12.6
1.2
2.2
0.21
0.31
0.50
202.5
10
0.1
0.1
207.5
40
V
µs
µs
V
mV
nA
µA
µA
Note 2: Output in regulation, VOUT = VOUT (nominal) ±4%.
Note 3: At high VIN to VOUT differentials, the maximum load current is limited by the maximum allowable power dissipation in the
package (see Absolute Maximum Ratings).
Note 4: Minimum value is production tested. Maximum value is guaranteed by design and is not production tested.
Note 5: VOUT is set to a target value of +5V by 0.1% external feedback resistors. VOUT is measured to be 5V ±2.5% to guarantee the
error comparator trip point.
Note 6: Start-Up guaranteed under these load conditions.
_______________________________________________________________________________________ 3

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Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, TA = +25°C, unless otherwise noted).
NO-LOAD SUPPLY CURRENT
vs. VOLTAGE AND TEMPERATURE
300
(SWITCH = OFF)
280
260 TA = +85°C
240
220
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE AND TEMPERATURE
80
70
60
50 TA = +85°C
MAX778L
SHDN THRESHOLD VOLTAGE
vs. INPUT VOLTAGE AND TEMPERATURE
3.5
3.0
2.5
TA = +125°C
200 40 2.0
180
160
140
120
100
1
TA = +25°C
TA = -40°C TA = 0°C
23
45
SUPPLY VOLTAGE (V)
6
7
30
20 TA = 0°C
10
TA = -40°C
0
1 23
45 67
INPUT VOLTAGE (V)
1.5
1.0
0.5
1
TA = +25°C
TA = -55°C
23
45
INPUT VOLTAGE (V)
6
7
MAX777L/MAX779L
EFFICIENCY vs. LOAD CURRENT
90
VOUT = 5V
80
MAX778L
EFFICIENCY vs. LOAD CURRENT
90
VOUT = 3.3V OR 3.0V
80
70 70
60 60
50
40
30
0.1
VIN = 4V
VIN = 2.5V
VIN = 1.8V
VIN = 1.5V
VIN = 1.1V
1 10 100
LOAD CURRENT (mA)
1000
MAX777L/MAX779L
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
300
VOUT = 5V
250
200
150
100
50
50
40
30
0.1
VIN = 2.5V
VIN = 1.8V
VIN = 1.5V
VIN = 1.1V
1 10 100
LOAD CURRENT (mA)
1000
MAX778L
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
350
VOUT = 3.3V
300
250
200
150
100
50
0
0.5 1.0 1.5 2.0 2.5
INPUT VOLTAGE (V)
0
0.5 1.0 1.5
INPUT VOLTAGE (V)
2.0
4 _______________________________________________________________________________________

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Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
LINE-TRANSIENT RESPONSE
AA
2ms/div
A: IOUT, 200mA/div, 0mA to 200mA
B: VOUT, 50mV/div, AC COUPLED
MAX778L, VOUT = 3.3V, VIN = 2.5V
B
SWITCHING WAVEFORMS,
CONTINUOUS CONDUCTION
A
5µs/div
A: SWITCH VOLTAGE (LX PIN), 2V/div
B: INDUCTOR CURRENT, 0.5A/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div, AC COUPLED
MAX777L, VIN = 1.5V, IOUT = 100mA
B
0mA
C
B
2ms/div
A: VIN, 1V/div, 1.8V to 3.3V
B: VOUT, 100mV/div, AC-COUPLED, IOUT = 240mA
MAX778L, VOUT = 3.3V
SWITCHING WAVEFORMS,
DISCONTINUOUS CONDUCTION
A
B
C
2µs/div
A: SWITCH VOLTAGE (LX PIN), 2V/div
B: INDUCTOR CURRENT, 0.5A/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div, AC COUPLED
MAX777L, VIN = 3V, IOUT = 70mA
_______________________________________________________________________________________ 5