Maxim > Design Support > Technical Documents > Application Notes > Battery Management > APP 680
Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 680
Keywords: linear, switch-mode, battery charger, microcontroller, current source, switching dc-dc
converter, notebook computer, lithium-ion, Li+, lithium, 8051, NiCd, NiMH, Nickel Metal Hydride,
Microchip PIC, voltage regulator, current regulators
APPLICATION NOTE 680
How to Design Battery Charger Applications that
Require External Microcontrollers and Related
System-Level Issues
Jul 22, 2002
Abstract: Notebook computers increasingly require complex battery charging algorithms and systems.
This article provides information and background on lithium-ion (Li+), nickel-cadmium (NiCd), and nickel-
metal-hydride (NiMH) batteries and related system-level switch-mode and linear battery chargers. These
voltage regulators and current regulators are controlled by external microprocessors like the 8051 or
Microchip PIC, and examples are provided with these controllers. An overview of requirements for
charging common battery chemistries with Maxim battery charger ICs is provided, along with a
discussion of system-level trade-offs and firmware design tips, and a list of World Wide Web engineering
resources.
The previous issue of Maxim's Engineering Journal (Vol. 27) discussed new developments in stand-alone
battery chargers. This second article of a two-part series explores the system-level issues in applying
battery-charger ICs.
Over the past five years, market pressures on portable equipment have transformed the simple battery
charger into a sophisticated switch-mode device capable of charging an advanced battery in 30 minutes.
This development also marks a departure from the self-contained, stand-alone charger ICs of only a few
years ago. Some of those ICs included considerable intelligence: enough to handle the complex task of
fast charging advanced batteries.
Maxim still manufactures stand-alone charger ICs, but market demand has changed recently. Today's
battery-charger subsystems regulate charging voltage and current using the intelligence of an external
microcontroller (µC), usually available elsewhere in the system. This approach achieves low cost in high-
volume applications and allows the greatest flexibility in tailoring the charger to a specific application.
All necessary intelligence once resided in the battery-charger controller IC itself, but now the system
designer must implement a charging algorithm and write the associated firmware. This article provides
the information and background necessary to implement charger systems based on Maxim's wide range
of battery-charger ICs for all popular chemistries.
The following discussion presents an overview of the requirements for charging common battery
chemistries with Maxim battery-charger ICs. It addresses system-level trade-offs and firmware design
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