Intersil's narrow VDC battery charger controller extends battery life in notebook computers

The only true narrow VDC charger controller on the market, the ISL6257 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 the adapter voltage, increasing the overall efficiency of the system and improving battery life and thermal management in the system.



Intersil’s ISL6257 provides +0.5% charge voltage accuracy (-10 to +100 degrees C) for precise charge voltage, increasing battery life. The 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.

Simplifying the design process, the ISL6257 provides a fixed 300kHz PWM (pulse width modulation) synchronous buck controller with diode emulation at light load. 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 device has a fast input current limit response to prevent over-current shutdown of the adapter, and its input voltage range from 7V to 25V supports most adapters. The ISL6257 also supports 2, 3 and 4-cell battery packs, meeting 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. The device also has a +25% accurate battery trickle charge current limit.



The aircraft power capable device features thermal shutdown, both AC and DC adapter present indication, battery discharge MOSFET control, and support for pulse charging.



The ISL6257 will charge any battery chemistry: Li-Ion, NiCd, NiMH, etc. Other features include programmable charge current limit, adapter current limit and charge voltage, up to 17.64V battery-voltage set point, control adapter power source select MOSFET, and less than 10μA battery leakage current.



Target applications for the ISL6257 are notebook, desknote and sub-notebook computers, and personal digital assistants. The device is available now in a 28-lead QFN package. Pb-free plus anneal is available (RoHS compliant).