CONSONANCE CN3762

CN3762 is a PWM step-down two-cell lithium battery charge management IC featuring trickle, constant current, and constant voltage charging modes. The constant current charge current is set by the current sensing resistor R_CS between the CSP pin and BAT pin. In constant voltage charging mode, the constant voltage charging voltage can be adjusted upward via a resistor between the BAT pin and FB pin; when the BAT pin is connected directly to the FB pin, the constant voltage charging voltage is 8.4V with 1% accuracy.

CN3762 operates normally when the VCC pin voltage exceeds the UVLO threshold and is greater than the battery voltage. If the battery voltage falls below the trickle charge threshold, the charger automatically enters trickle charging mode, where the charge current is 17.5% of the programmed constant current. When the battery voltage exceeds the trickle charge threshold, the charger enters constant current charging mode, where the charge current is determined by the internal 120mV reference voltage and external resistor R_CS, i.e., charge current = 120mV/R_CS. As the battery voltage continues to rise and approaches the constant voltage charging voltage, the charger enters constant voltage charging mode and the charge current gradually decreases. During charging, the transistor inside the open-drain output pin turns on and pulls the output low to indicate charging status. When the charge current decreases to 16% of the constant current, charging terminates and the DRV pin outputs high. The transistor inside one open-drain output pin turns off, placing the output in a high-impedance state; the transistor inside the other open-drain output pin turns on and pulls the output low to indicate charge termination status. In the charge termination state, disconnecting and reconnecting the input power supply will initiate a new charge cycle; if the battery voltage drops to the recharge threshold, a new charge cycle will also start automatically.

When the input voltage is removed, CN3762 automatically enters sleep mode and the internal circuitry is shut down.

CN3762 also incorporates an overvoltage comparator. When the BAT pin voltage rises due to load changes or sudden battery removal, if the BAT pin voltage rises to 1.07 times the constant voltage charging voltage, the overvoltage comparator activates and turns off the external P-channel MOSFET, temporarily halting the charger until the BAT pin voltage returns below 1.02 times the constant voltage charging voltage.

• For deeply discharged Li-ion batteries, trickle charging is applied at 17.5% of the set constant-current charge current when the battery voltage falls below 66.5% (typical) of the constant-voltage charge voltage
• During the constant-voltage charging phase, the charge current gradually decreases; charging terminates when the current drops to 16% of the constant-current charge current
• In the charge termination state, a new charge cycle starts automatically if the battery voltage drops to 95.5% of the constant-voltage charge voltage
• Automatically enters sleep mode when input power is lost or input voltage falls below battery voltage
• Other features include input undervoltage lockout, battery terminal overvoltage protection, and charge status indication
• 10-pin SSOP package
• Wide input voltage range: 6.6V to 30V
• Complete charge management for two series Li-ion cells
• Charge current up to 4A
• PWM switching frequency: 300KHz
• Constant-voltage charge voltage adjustable upward via resistor
• Constant-voltage charge voltage accuracy: ±1%
• Constant-current charge current set by external resistor
• Trickle charging for deeply discharged batteries
• Automatic recharge function
• Charge status and charge termination status indication
• Soft-start function
• Battery terminal overvoltage protection
• Operating temperature range: -40℃ to +85℃
• Lead-free, RoHS compliant, halogen-free

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