Battery charger controller improves efficiency and extends battery life

Intersil introduces the ISL6257, a narrow VDC (voltage direct current) charger controller for Li-Ion/Li-Ion polymer batteries in notebook computers. This device is designed to meet the NVDC-I requirements for better efficiency and longer battery life.

The ISL6257, the only true narrow VDC charger controller on the market, offers the best overall accuracy and features narrow VDC output, which allows the system to operate from the regulated charger instead of the adapter. The use of the Vbat as the system voltage as opposed to the adapter allows the notebook to run at a maximum of 12.6V instead of adapter voltage, increasing the overall efficiency of the system and improving battery life and thermal management in the system.

“The ISL6257 is the only NVDC-I charger on the market that is optimized for this application, allowing customers to run their laptops at much lower battery voltages,” said Majid Kafi, director of Intersil's Notebook Power products group. “This provides better efficiency, longer battery life and improved thermal management.”

Battery Charger Controller

Intersil's ISL6257 provides ±0.5% charge voltage accuracy (-10°C to +100°C) for precise charge voltage, increasing battery life. This device also provides a ±3% accurate battery charge current limit for precise charge current control, allowing the maximum charge rate and further extending battery life.

The ISL6257 provides a fixed 300kHz PWM (pulse width modulation) synchronous buck controller with diode emulation at light load. This constant frequency simplifies the design process. Diode emulation improves efficiency and prevents adapter voltage boosting. This feature is not present on many competitors' parts.

The ISL6257 has a type III output voltage control system that allows the regulated output to respond quickly to transient loads with minimal change in output voltage. This reduces the power supply rejection requirements for all downstream power supplies. No other charger offers this feature.

The ISL6257 has a fast input current limit response to prevent over-current shutdown of the adapter. The device's input voltage range from 7V to 25V supports most adapters. The ISL6257 also supports 2-, 3- and 4-cell battery packs, which meets most notebook battery pack requirements.

A ±3% accurate input current limit provides precise input current and allows higher charge rates without exceeding the adapter current limit. This device also has a ±25% accurate battery trickle charge current limit.

Key Features

±0.5% charge voltage accuracy (-10°C to +100°C)
±3% accurate input current limit
±3% accurate battery charge current limit
±25% accurate battery trickle charge current limit
Programmable charge current limit, adapter current limit and charge voltage
Fixed 300kHz PWM synchronous buck controller with diode emulation at light load
AC adapter present indicator
Fast input current limit response
Input voltage range 7V to 25V
Support 2-, 3- and 4-cells battery packs
Up to 17.64V battery-voltage set point
Control adapter power source select MOSFET
Thermal shutdown
Aircraft power capable
DC adapter present indicator
Battery discharge MOSFET control
Less than 10μA battery leakage current
Support pulse charging
Charge any battery chemistry: Li-Ion, NiCd, NiMH, etc.
Pb-free plus anneal available (RoHS compliant)

The controller is targeted at notebook, desknote and sub-notebook computers, as well as personal digital assistants.

To learn more, visit Intersil's power management page at

The ISL6257 is available now in a 28-lead QFN package and is priced at $3.42 in 1,000-unit quantities. For more information on the ISL6257, visit,1477,ISL6257,0.html.

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