Features: 1V to 4.5V Input Guarantees Start-Up Under Load
Up to 210mA Output
Load Fully Disconnected in Shutdown
82% Efficiency
Output in Regulation with Input Voltage above Output Voltage
Internal 1A Power Switch and Active Rectifier
Adjustable Current Limit Allows Low-Cost Inductors
190A No Load Supply Current
20A Shutdown Supply Current
3V/3.3V (MAX778L), 5V (MAX777L), and Adjustable (MAX779L) Output VoltageApplicationSingle 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 ComputersPinout
SpecificationsABSOLUTE 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.
DescriptionThe MAX777L/MAX778L/MAX779L are pulse-skipping DC-DC converters that step up from low-voltage inputs (1V uaranteed). They require only three external components-an inductor (typically 22H) 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 MAX779L 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 AX777L/MAX778L/MAX779L's Active RectifierTM turns off in the shutdown mode, disconnecting the output from the source. This eliminates the current drain associated with conventional step-up converters when off or in shutdown.
High-frequency operation of MAX779L (up to 150kHz) allows the use of small, surface-mount inductors with values of 10H or less. Supply current is 190A under no load and only 20A in standby 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 output), refer to the MAX877L/MAX878L/MAX879L data sheet.
MAX779L Data Sheet
