MAX777L Datasheet, PDF (1/12 Pages) Maxim Integrated Products – Low-Voltage Input, 3V/3.3V/5V/ Adjustable Output, Step-Up DC-DC Converters

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 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.
________________________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
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