(ACTIVE) High Efficiency Synchronous Switch-Mode Charger Controller – Solar Battery Charger


Functional Diagram


The bq24650 device is a highly integrated switch-mode battery charge controller. It provides input voltage regulation, which reduces charge current when input voltage falls below a programmed level. When the input is powered by a solar panel, the input regulation loop lowers the charge current so that the solar panel can provide maximum power output.

The bq24650 offers a constant-frequency synchronous PWM controller with high accuracy current and voltage regulation, charge preconditioning, charge termination, and charge status monitoring.

The bq24650 charges the battery in three phases: pre-conditioning, constant current, and constant voltage. Charge is terminated when the current reaches 1/10 of the fast charge rate. The pre-charge timer is fixed at 30 minutes. The bq24650 automatically restarts the charge cycle if the battery voltage falls below an internal threshold and enters a low quiescent current sleep mode when the input voltage falls below the battery voltage.

The bq24650 supports a battery from 2.1 V to 26 V with VFB set to a 2.1-V feedback reference. The charge current is programmed by selecting an appropriate sense resistor. The bq24650 is available in a 16 -pin, 3.5 mm × 3.5 mm2 thin QFN package.


  • Maximum Power Point Tracking (MPPT)
    Capability by Input Voltage Regulation
  • Programmable MPPT Setting
  • 5-V to 28-V Input Solar Panel
  • 600-kHz NMOS-NMOS Synchronous Buck
  • Resistor Programmable Float Voltage
  • Accommodates Li-Ion/Polymer, LiFePO4, Lead Acid Chemistries
  • Accuracy
    • ±0.5% Charge Voltage Regulation
    • ±3% Charge Current Regulation
    • ±0.6% Input Voltage Regulation
  • High Integration
    • Internal Loop Compensation
    • Internal Digital Soft Start
  • Safety
    • Input Overvoltage Protection
    • Battery Temperature-Sensing
    • Battery Absent Detection
    • Thermal Shutdown
  • Charge Status Outputs for LED or Host Processor
  • Charge Enable on MPPSET Pin
  • Automatic Sleep Mode for Low Power
    • < 15-µA OFF-State Battery Discharge Current
  • Small 3.5 × 3.5 mm2 16-Pin QFN Package

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Number of Series Cells 1^2^3^4^5^6    
Function Charger    
Cell Chemistry Lead Acid^Li-Ion/Li-Polymer^LiFePO4    
Charge Current (Max) (A) 20    
Operating Vin (Min) (V) 5    
Operating Vin (Max) (V) 28    
Absolute Vin (safety rating) (Max) ((V)) 33    
Battery Charge Voltage (Min) (V) 2.1    
Battery Charge Voltage (Max) (V) 26    
Features OVP^Programmable MPPT Setting^Solar Input^Temp Monitoring (Thermistor Pin)^UVLO^VINDPM    
Control Interface Standalone (RC-Settable)    
Control Topology Switch-Mode Buck    
Rating Catalog    
Operating Temperature Range (C) -40 to 85    
Pin/Package 16VQFN    

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Technical Documents

Datasheet (1)

Application notes (14)

User guides (1)

Selection guides (1)

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