CN3387

CN3387 is a PFM boost-type NiMH battery charge control IC capable of managing the charging of 4 to 12 NiMH cells. The input voltage range is 2.7V to 6.5V. The device integrates an internal voltage reference, inductor current sensing unit, battery voltage detection circuit, output overvoltage protection circuit, battery undervoltage protection unit, control unit, and external MOSFET driver circuit, making it highly suitable for 5V input multi-cell NiMH battery charging control applications. Key advantages include minimal external components, rich functionality, and simple circuit design. When input power is connected, CN3387 enters constant-current charging mode. The STAT pin outputs a high level, the external N-channel MOSFET turns on, the inductor current rises, and energy in the output capacitor is transferred to the battery. When the inductor current rises to the upper limit set by the external current sense resistor, the external N-channel MOSFET turns off, the inductor current decreases, and energy stored in the inductor is transferred to the output capacitor and battery. When the inductor current falls to the lower limit set by the external current sense resistor, the external N-channel MOSFET turns on again, repeating this cycle. The battery voltage is fed back to the FB pin of CN3387 through a resistor divider network. When the FB pin voltage reaches 1.125V (typical), CN3387 enters trickle charge mode, the input current drops to 66% of that during constant-current charging, and the internal timer is activated. When the internal timer expires or the FB pin voltage reaches 1.205V, the charging process terminates, the external N-channel MOSFET turns off, and CN3387 enters the charge termination state with the STAT pin outputting a low level. In the charge termination state, no current flows from the input to the battery. When the FB pin voltage falls below the recharge threshold of 1.105V (typical), CN3387 re-enters charging mode. CN3387 supports a maximum operating frequency of up to 1MHz. CN3387 is a boost-type charge control IC; under normal conditions, the battery voltage is higher than the input voltage. In certain situations where the battery voltage drops below the input voltage, or even in the event of a battery short circuit, the off-time of the external N-channel MOSFET is extended and the charging current is reduced, providing battery protection. Additional features include a chip enable input and battery terminal overvoltage protection.

Applications

• Standalone NiMH battery charger
• Power tools
• Toys
• Suitable for solar-powered applications

Key features

• When input power is connected, CN3387 enters constant-current charging mode, turning on the external N-channel MOSFET. The inductor current rises until it reaches the upper limit set by the external current sensing resistor, at which point the external N-channel MOSFET turns off and the inductor current falls, transferring energy from the inductor to the battery. When the inductor current drops to the lower limit set by the external current sensing resistor, the external N-channel MOSFET turns on again, repeating the cycle.
• When the FB pin voltage reaches 1.125V (typical), CN3387 enters maintenance charging mode. The input current is reduced to 66% of the constant-current level, and the internal timer is activated.
• When the internal timer expires or the FB pin voltage reaches 1.205V, the charging process ends and the external N-channel MOSFET remains off.
• When the FB pin voltage drops to the recharge threshold (1.105V), CN3387 re-enters charging mode.
• Maximum operating frequency up to 1MHz.
• Operating temperature range: －40℃ to +85℃.
• When the battery voltage is lower than the input voltage or a battery short circuit occurs, CN3387 continues to charge the battery with a reduced current through the combined action of the external N-channel and P-channel MOSFETs, providing battery protection.
• Additional features include chip enable input and charge status indicator output.
• CN3387 is available in a 10-pin SSOP10 package.