Power Electronics

Spotlight on Battery-Charger ICs

Li-Ion/Li-Polymer Chargers

Microchip Technology's MCP73837 and MCP73838 dual-input, high-current Li-ion/Li-polymer charge-management controllers feature automatic USB or ac-adapter power-source selection. These single-cell fully integrated chargers enable charge currents up to 1 A from an ac power source, plus charging currents up to 100 mA or 500 mA from a USB port.

On-chip safety features include thermal regulation, cell-temperature monitoring and charge timers to minimize charger-related system damage, resulting in safer and more-efficient charger designs.

The 73837 and 73838 chargers are available in 10-pin MSOP and 3-mm × 3-mm DFN packages, for $0.89 each in 10,000-unit quantities. The 73837 and 73838 evaluation board is also available.
Microchip Technology
Chandler, Ariz.


USB/AC Battery-Charger ICs

Advanced Analogic Technologies' USB/ac battery-charger ICs are designed for systems operating off single-cell 4.2-V Li-ion/Li-polymer batteries. The AAT3683 charger is rated for 1 A and operates from an input range of 4 V to 6.5 V. The AAT3684 is a single-input adapter/charger, programmable from 15 mA to 500 mA. The AAT3684-1 version comes without trickle-charge capability.

The AAT3681A supports up to 500 mA from either a USB or an ac source and is available in an 8-pin, 2-mm × 2.1-mm SC70JW package for $0.81 each. The AAT3683 is available in 10-pin, 2.2-mm × 2.2-mm STDFN and 16-pin, QFN-33 packages, and is $0.98 each. The AAT3684 is available in a 10-pin, 2.2-mm × 2.2-mm STDFN package and is $0.92 each. All pricing is for 1000-piece quantities.
Advanced Analogic Technologies
Sunnyvale, Calif.


Linear USB Power Manager

Linear Technology's LTC3557 is a multifunction power manager for Li-ion/Li-polymer battery applications. The PowerPath manager transitions among multiple input sources. For fast charging, the linear battery charger delivers up to 1.5 A from a wall-adapter supply or up to 500 mA from a USB port.

The LTC3557 features three integrated synchronous bucks with adjustable output voltages down to 0.8 V. The switching frequency is 2.25 MHz, and low on-resistance switches enable efficiencies up to 95%. The LTC3557 comes in a 0.75-mm profile, 4-mm × 4-mm QFN-28 package and is priced starting at $3.95 each in 1000-piece quantities.
Linear Technology
Milpitas, Calif.


Integrated Charger and Power Switch

The NUS3116 from ON Semiconductor is an integrated-charging and power-switching circuit for portable electronics. The NUS3116 integrates a main power switch, -12-V, -6.2-A µCool single p-channel MOSFET and two internal low-saturation pnp transistors.

The main-switch MOSFET features a 40-mΩ maximum on-resistance. Available in a DFN-8 package, the NUS3116 is priced at $0.80 each in 3000-unit quantities.
ON Semiconductor


Battery-Charger Front Ends

Texas Instruments' bq24314 and bq24316 battery-charger front-end ICs protect a system from input overvoltage, overcurrent and battery overvoltage conditions, which may result from a power spike during charging, or a defective or incorrect wall adapter. If input overvoltage is detected, the ICs remove power from the charging circuit by turning off an internal switch.

In the case of an overcurrent condition, the chips limit the system current at a user-programmable threshold value and — if the condition persists — switch the pass element off. If battery overvoltage is detected, the chips interrupt the input-charging source until the battery voltage returns to a safe level. The bq24314 and bq24316 can also report the status of a fault to the host processor.

Input overvoltage threshold is either 5.85 V (bq24314) or 6.8 V (bq24316). In quantities of 1000, the chips are priced at $0.75 each.
Texas Instruments


Lithium-Ion Fuel Gauge

The DS2784 from Maxim Integrated Products is a single-cell stand-alone fuel gauge for integrating a Li-ion/Li-polymer protector and SHA-1 authentication. The DS2784 is ideal for space-sensitive portable applications that use single-cell lithium battery packs.

The fuel gauge estimates available capacity based on coulomb count, discharge rate, temperature and cell characteristics. The DS2784 is available in a 3-mm × 5-mm, 14-pin TDFN package. Prices start at $2.94 each in quantities of 1000.
Maxim Integrated Products
Sunnyvale, Calif.


Overcurrent-Protection ICs

The single-chip ISL9208 and ISL9216/17 chipset from Intersil provide both cell balancing and overcurrent protection in multicell Li-ion battery packs. The ISL9208 is recommended for 5- to 7-cell (18- to 28-V) battery packs, while the ISL9216/17 chipset is recommended for 7- to 12-cell (28- to 50-V) battery packs.

The ISL9208 is available in a 32-lead, 5-mm × 5-mm QFN configuration for $2.27 each. The ISL9216 is available in a 32-lead, 5-mm × 5-mm QFN package for $3 each. The ISL9217 is available in a 24-lead, 4-mm × 4-mm QFN configuration for $2.93 each. All prices are for quantities of 100 to 1000.
Milpitas, Calif.

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