The bq24751A is a high-efficiency, synchronous battery charger with integrated compensation and system power selector logic, offering low component count for space-constrained multi-chemistry battery charging applications. Ratiometric charge current and voltage programming allows very high regulation accuracies, and can be either hardwired with resistors or programmed by the system power-management microcontroller using a DAC or GPIOs.
The bq24751A charges two, three, or four series Li+ cells, supporting up to 10 A of charge current, and is available in a 28-pin, 5x5-mm thin QFN package.
The bq24751A controls external switches to prevent battery discharge back to the input, connect the adapter to the system, and to connect the battery to the system using 6-V gate drives for better system efficiency. For maximum system safety, inrush-power limiting provides instantaneous response to high input voltage multiplied by current. This AC Over-Power protection (ACOP) feature limits the input-switch power to the programmed level on the ACOP pin, and latches off if the high-power condition persists to prevent overheating.
The bq24751A 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 adapter 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 to monitor the overall system power.
Feature
- 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
- Automatic System Power Selection From AC/DC Adapter or Battery
- Internal Loop Compensation
- Internal Soft Start
- Safety
- Programmable Input Overvoltage Protection (OVP)
- Dynamic Power Management (DPM) with Status Indicator
- Programmable Inrush Adapter Power (ACOP) and Overcurrent (ACOC) Limits
- Reverse-Conduction Protection Input FET
- Supports Two, Three, or Four Li+ Cells
- 5 - 24 V AC/DC-Adapter Operating Range
- Analog Inputs with Ratiometric Programming via Resistors or DAC/GPIO Host Control
- Charge Voltage (4-4.512 V/cell)
- Charge Current (up to 10 A, with 10-m sense resistor)
- Adapter Current Limit (DPM)
- Status and Monitoring Outputs
- AC/DC Adapter Present with Programmable Voltage Threshold
- Current Drawn from Input Source
- Battery Learn Cycle Control
- Supports Any Battery Chemistry: Li+, NiCd, NiMH, Lead Acid, etc.
- Charge Enable
- 28-pin, 5x5-mm QFN package
- Energy Star Low Iq
- < 10-μA Off-State Battery Discharge Current
- < 1.5-mA Off-State Input Quiescent Current
- APPLICATIONS
- Notebook and Ultra-Mobile Computers
- Portable Data Capture Terminals
- Portable Printers
- Medical Diagnostics Equipment
- Battery Bay Chargers
- Battery Back-up Systems
