The bq24745 is a high-efficiency, synchronous battery charger with an integrated input-current comparator, offering low component count for space-constrained, multi-chemistry battery-charging applications. The input-current, charge-current, and charge-voltage DACs allow very high regulation accuracies that can be easily programmed by the system power-management microcontroller using the SMBus interface. The bq24745 charges two, three, or four series Li+ cells, and is available in a 28-pin, 5-mm × 5 mm QFN package.

The bq24745 features dynamic power management (DPM) and input power limiting. These features reduce battery-charge current when the input power limit is reached to avoid overloading the ac adaptor when supplying the load and the battery charger simultaneously. A highly accurate current-sense amplifier enables precise measurement of input current from the ac adapter, allowing monitoring the overall system power. If the adapter current is above the programmed low-power threshold, a signal is sent to host so that the system optimizes its performance to the power available from the adapter. An integrated comparator monitors the input current through the current-sense amplifier, and indicates when the input current exceeds a programmable threshold limit.

• NMOS-NMOS Synchronous Buck Converter with 300-kHz Frequency and >95% Efficiency
• 30-ns Minimum Driver Dead-Time and 99.5% Maximum Effective Duty Cycle
• High-Accuracy Voltage and Current Regulation
  • ±0.5% Charge Voltage Accuracy
  • ±3% Charge Current Accuracy
  • ±3% Adapter Current Accuracy
  • ±2% Input Current Sense Amp Accuracy
• Integration
  • Input Current Comparator, With Adjustable Threshold and Hysteresis
  • Internal Soft-Start
• Safety
  • Dynamic Power Management (DPM)
• Up to 19.2-V Battery Voltage
• 7-V–24-V AC/DC-Adapter Operating Range
• Simplified SMBus Control Interface
  • Charge Voltage DAC (1.024 V–19.2 V)
  • Charge Current DAC (128 mA–8.064 A)
  • Adapter Current Limit DPM DAC (256 mA–11.008 A)
• Status and Monitoring Outputs
  • AC/DC Adapter Present With Adjustable Voltage Threshold
  • Input Current Comparator With Adjustable Threshold and Hysteresis
  • Current Sense Amplifier for Current Drawn From Input Source
• Charge Any Battery Chemistry: Li+, NiCd, NiMH, Lead Acid, Etc.
• Charge Enable Pin
• < 10-µA Battery Current With Adapter Removed
• < 1-mA Input DCIN Current With Adapter Present and Charge Disabled
• 28-Pin, 5-mm × 5-mm QFN Package