LTC1558-3.3

Features:

Complete Battery Backup System in an SO-8, 16-Pin GN or SO Package
Generates Adjustable Backup Voltage from a Single 1.2V NiCd Button Cell
Automatic Main Supply to Backup Switching
Minimum 100mW Output Power
Automatic Fast Recharge of NiCd Battery
Programmable NiCd Trickle Charge Current
Smart NiCd 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


Application

Notebook Computers
Palmtop Computers/PDAs
Portable Instruments
Battery-Powered Systems


Pinout




Specifications

V_CC ...................................................................... 6V
V_BAK, BACKUP .................................................... 12V
SW ......................................................................14V
All Other Pins ............................ -0.3V to V_CC + 0.3V
Input Currents (SW) ......................................500mA
VBAK Output Current ............Short-Circuit Protected
Operating Ambient Temperature Range .. 0 to 70
Junction Temperature .......................................125
Storage Temperature Range ..............65 to 150
Lead Temperature (Soldering, 10 sec)...............300


Description

The LTC®1558 is a backup battery controller that provides all the functions necessary to implement a backup power supply using a single NiCd 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 NiCd cell.

The on-chip NiCd 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 compensate 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.