LTC1558-5 Datasheet | Linear Technology

LTC1558-3.3/LTC1558-5 Backup Battery Controller with Programmable Output Features s s DESCRIPTION The LTC®1558 is a backup battery controller that provides all the functions necessary to implement a backup power supply using a single Ni Cd cell. It includes a 1.2V boost converter, an intelligent 2-stage battery charger, automatic backup switching and a microprocessor reset generator. The boost converter uses a synchronous switching architecture to achieve a typical efficiency of 70%, ensuring maximum backup lifetime from a small Ni Cd cell. The on-chip Ni Cd charger uses an internal gas gauge to minimize fast recharge time and prevent overcharging of the backup cell. The LTC1558 also provides a user programmable trickle charge current to pensate for self discharge losses in the backup cell. The LTC1558’s automatic backup switching architecture requires minimum intervention from the host system and provides feedback to the host to minimize system loading in the backup state. Its internal VCC fault detector and reset generator eliminate the need for a separate microprocessor supervisory chip in most applications. The LTC1558 is available in an SO-8, 16-lead GN or SO package. , LTC and LT are registered trademarks of Linear Technology Corporation. s s s s s s s s s s plete Battery Backup System in an SO-8, 16-Pin GN or SO Package Generates Adjustable Backup Voltage from a Single 1.2V Ni Cd Button Cell Automatic Main Supply to Backup Switching Minimum 100m W Output Power Automatic Fast Recharge of Ni Cd Battery Programmable Ni Cd Trickle Charge Current Smart Ni Cd Charger Minimizes Recharge Time and Maximizes System Efficiency After Backup On-Chip Power-On Reset Pushbutton Reset Input Reset Assertion Guaranteed at VCC = 1V Short-Circuit Protection Thermal Limiting U APPLICATIONS s s s s Notebook puters Palmtop puters/PDAs Portable Instruments Battery-Powered Systems TYPICAL APPLICATION L1 22µH- 1.2V Ni Cd BACKUP - - BATTERY + C1 1µF R1 14k LTC1558-3.3 1 2...