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MAX879 Dataheets PDF



Part Number MAX879
Manufacturers Maxim
Logo Maxim
Description Step-Up/Step-Down DC-DC Converters
Datasheet MAX879 DatasheetMAX879 Datasheet (PDF)

19-0204; Rev 1; 5/94 NUAL KIT MA ATION U EET L H A S V A E T WS DA FOLLO 5V/3.3V/3V/Adjustable-Output, Step-Up/Step-Down DC-DC Converters ____________________________Features o Regulates from Inputs Above & Below the Output o 1V to 6.2V Supply-Voltage Range o Internal 1A Active Rectifier with Input-to-Output Disconnect in Shutdown o Up to 210mA Load Currents, Guaranteed o 85% Efficiency o Only 3 External Components o Adjustable Current Limit o 195µA Quiescent Supply Current o 20µA Shutdown Sup.

  MAX879   MAX879



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19-0204; Rev 1; 5/94 NUAL KIT MA ATION U EET L H A S V A E T WS DA FOLLO 5V/3.3V/3V/Adjustable-Output, Step-Up/Step-Down DC-DC Converters ____________________________Features o Regulates from Inputs Above & Below the Output o 1V to 6.2V Supply-Voltage Range o Internal 1A Active Rectifier with Input-to-Output Disconnect in Shutdown o Up to 210mA Load Currents, Guaranteed o 85% Efficiency o Only 3 External Components o Adjustable Current Limit o 195µA Quiescent Supply Current o 20µA Shutdown Supply Current o 3V/3.3V/5V and Adjustable Output Voltage Versions o Available in 8-Pin DIP and SO Packages _______________General Description The MAX877/MAX878/MAX879 are pulse-skipping, stepup/step-down DC-DC converters that provide a regulated output from inputs both above and below the output. They require only three external components—an inductor (typically 22µH) and two filter capacitors. The MAX877 delivers a regulated 5V output from 2.5V to 6.2V inputs. The MAX878 generates pin-selectable voltages of 3.0V or 3.3V from 1.5V to 6.2V inputs. The MAX879 output can be adjusted from 2.5V to 6V via an external resistor divider from 2.5V to 6.2V inputs. A unique high-power, internal, synchronous rectifier design (Active Rectifier™) enables the devices to regulate in a switched linear mode if the input voltage is higher than the desired output voltage. When the input voltage falls below the output voltage, the MAX877/MAX878/MAX879 will smoothly switch into a pulse-skipping boost mode and step up from input voltages as low as 1V. In shutdown, the active rectifier disconnects the output from the source. This stops the current drain from input to output associated with conventional step-up converters. High-frequency operation (up to 300kHz) allows the use of small surface-mount inductors. Supply current is 195µA under no load, and only 20µA in shutdown mode. For 1-cell (1V) step-up converters with similar performance and the same pinout, refer to the MAX777/MAX778/MAX779 data sheet. MAX877/MAX878/MAX879 ______________Ordering Information PART MAX877CPA MAX877CSA MAX877C/D MAX877EPA MAX877ESA MAX877MJA 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 Two or Three NiCd Cells to 3V/3.3V Conversion Three or Four Alkaline Cells to 5V Conversion One Lithium Cell to 3V/3.3V Conversion Pagers Palmtop and Notebook Computers Battery-Powered and Hand-Held Instruments Ordering Information continued on last page. * Contact factory for dice specifications. __________Typical Operating Circuit __________________Pin Configuration TOP VIEW INPUT 1.8V TO 6.2V 2 22µF IN ILIM MAX878 SHDN SEL 8 PGND 4 LX OUT AGND 3 5 6 22µH ILIM 1 IN 2 AGND 3 PGND 4 8 N.C. (MAX877)* SHDN ON/OFF OUT LX 1 7 MAX877 MAX878 MAX879 7 6 5 OUTPUT 3.3V 210mA 100µF DIP/SO * SEL (MAX878), FB (MAX879) ™ Active Rectifier is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products 1 Call toll free 1-800-998-8800 for free samples or literature. http://www.Datasheet4U.com/ 5V/3.3V/3V/Adjustable-Output, Step-Up/Step-Down DC-DC Converters MAX877/MAX878/MAX879 ABSOLUTE MAXIMUM RATINGS Supply Voltage (IN to PGND) .......................................0V to +7V Output Short-Circuit Duration to PGND, AGND (Note 1)....30sec Voltage Applied to: LX (switch off).......................................................-0.3V to +7V (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: MAX87_C_A ........................................................0°C to +70°C MAX87_E_A .....................................................-40°C to +85°C MAX87_MJA ..................................................-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 continuously 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 impl.


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