CN3781

CN3781 is a PWM buck-mode single-cell lithium battery charge management IC that independently manages single-cell lithium battery charging. It features a compact package, minimal external components, and ease of use. CN3781 supports trickle, constant current, and constant voltage charging modes, making it ideal for lithium battery charge management. In constant voltage mode, CN3781 regulates the battery voltage to 4.2V, which can be adjusted upward via an external resistor; in constant current mode, the charge current is set by an external resistor. An internal adaptive circuit automatically adjusts the charge current based on the current output capability of the input power source, eliminating the need for worst-case design considerations. This maximizes utilization of the available current from various input sources, making it well suited for applications powered by current-limited supplies such as USB interfaces. For deeply discharged lithium batteries, when the battery voltage falls below 66.5% (typical) of the constant voltage charge threshold, CN3781 applies trickle charging at 17.5% of the programmed constant current charge value. During the constant voltage phase, the charge current gradually decreases; when it drops to 16% of the constant current charge value, charging terminates. In the charge termination state, if the battery voltage falls to 95.5% of the constant voltage charge threshold, a new charge cycle begins automatically. When the input power source is removed or the input voltage drops below the battery voltage, CN3781 automatically enters sleep mode. Additional features include input undervoltage lockout, battery overvoltage protection, and charge status indication. CN3781 is available in a 10-pin SSOP package.

Applications

• Power banks
• Handheld devices
• Backup battery applications
• Portable industrial and medical instruments
• Power tools
• Standalone battery chargers

Key features

• Internal adaptive circuitry automatically adjusts charging current based on the current output capability of the input power source
• Supports lithium battery charging from limited-current sources such as USB interfaces
• Wide input voltage range: 4.83V to 28V
• Complete charge management for single-cell lithium batteries
• Charging current up to 4A
• PWM switching frequency: 300KHz
• Constant-voltage charging voltage adjustable upward via external resistor
• Constant-voltage charging accuracy: ±1%
• Constant-current charging current set by external resistor
• Trickle charging for deeply discharged batteries
• Automatic recharge function
• Charge status and end-of-charge status indication
• Soft-start function
• Battery terminal overvoltage protection
• Operating temperature range: -40°C to +85°C
• 10-pin SSOP package
• Lead-free, RoHS compliant, halogen-free