Document
19-0186; Rev 2; 7/96
NUAL KIT MA ATION U EET L H A S V E TA WS DA FOLLO
Low-Voltage Input, 3V/3.3V/5V/ Adjustable Output, Step-Up DC-DC Converters
____________________________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
_______________General Description
The MAX777L/MAX778L/MAX779L are pulse-skipping DC-DC converters that step up from low-voltage inputs (1V guaranteed). They require only three external components—an inductor (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, 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 (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 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.
MAX777L/MAX778L/MAX779L
______________Ordering Information
PART MAX777LCPA MAX777LCSA MAX777LC/D MAX777LEPA MAX777LESA MAX777LMJA TEMP. RANGE 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -55°C to +125°C PIN-PACKAGE 8 Plastic DIP 8 SO Dice* 8 Plastic DIP 8 SO 8 CERDIP**
________________________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
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.
__________Typical Operating Circuit
INPUT 1V TO 4.5V
2
__________________Pin Configuration
TOP VIEW
22µF
IN ILIM MAX777L SHDN PGND 4 LX OUT AGND 3 5 6
22µH
ILIM 1 IN 2
8
N.C. (MAX777L)* SHDN OUT LX
1 7
ON/OFF
OUTPUT 5V
100µF
AGND 3 PGND 4
MAX777L MAX778L MAX779L
7 6 5
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
Low-Voltage Input, 3V/3.3V/5V/ Adjustable Output, Step-Up DC-DC Converters MAX777L/MAX778L/MAX779L
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 indi.