Bridge Battery Backup Controllers for Notebooks

The MAX1612/MAX1613 manage the bridge battery (sometimes called a hot-swap or auxiliary battery) in portable systems such as notebook computers. They feature a step-up DC-DC converter that boosts 2-cell or 3-cell bridge-battery voltages up to the same level as the main battery. This voltage boosting technique reduces the number of cells otherwise required for a 6-cell plus diode-OR bridging scheme, reducing overall size and cost. Another key feature is a trickle-charge timer that minimizes battery damage caused by constant charging and eliminates trickle-charge current drain on the main battery once the bridge battery is topped off.

These devices contain a highly flexible collection of independent circuit blocks that can be wired together in an autonomous stand-alone configuration or used in conjunction with a microcontroller. In addition to the boost converter and charge timer, there is a micropower linear regulator (useful for RTC/CMOS backup as well as for powering a microcontroller) and a high-precision low-battery detection comparator.

The two devices differ only in the preset linear-regulator output voltage: +5.0V for the MAX1612 and +3.3V for the MAX1613. Both devices come in a space-saving 16-pin QSOP package.

Applications

* Backup Battery Applications * Notebook Computers * Portable Equipment

* Reduce Battery Size and Cost

* Four Key Circuit Blocks

* Adjustable Boost DC-DC Converter

* NiCd/NiMH Trickle Charger

* Always-On Linear Regulator (+28V Input)

* Low-Battery Detector

* Low 18µA Quiescent Current

* Selectable Charging/Discharging Rates

* Preset Linear-Regulator Voltage

* 5V (MAX1612)

* 3.3V (MAX1613)

* 4V to 28V Main Input Voltage Range

* Internal Switch Boost Converter

* Small 16-Pin QSOP Package