Low-Voltage Input / 3V/3.3V/5V/ Adjustable Output / Step-Up DC-DC Converters - Maxim
Description
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/MA...
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