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_______________General Desc ription
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 Rectifier
TM
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 Rectifier
TM
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.
________________________Applic ations
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
__________Typic al Operating Circ uit
____________________________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
Ordering Information continued at end of data sheet.
* Dice are specified at T
A
= +25°C, DC parameters only.
**Contact factory for availability and processing to MIL-STD-883.
M
Low-Voltage Input, 3V /3.3V /5V /
Adjustable Output, S tep-Up DC-DC Converters
________________________________________________________________ Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
1
1
2
3
4
DIP/SO
TOP VIEW
MAX777L
MAX778L
MAX779L
8
7
6
5
N.C. (MAX777L)
*
SHDN
OUT
LX
ILIM
IN
AGND
PGND
*
SEL FOR MAX778L, FB FOR MAX779L.
__________________Pin Configuration
INPUT
1V TO 4.5V
IN
ILIM
SHDN
100μF
OUTPUT
5V
AGND
3
MAX777L
LX
OUT
PGND
4
22μH
ON/OFF
22
μ
F
1
2
7
6
5
19-0186; Rev 2; 7/96
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
MAX777L
CPA
MAX777LCSA
MAX777LC/D
MAX777LEPA
MAX777LMJ A
-55°C to +125°C
8 CERDIP**
MAX777LESA
-40°C to +85°C
8 SO
Active Rectifier is a trademark of Maxim Integrated Products.
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