CN3600

CN3600 is a fixed off-time PFM buck-mode single-cell NiMH battery charge management IC. The input voltage range is 2.7V to 6.5V. CN3600 integrates a voltage reference, inductor current sensing unit, battery voltage feedback network, battery overvoltage protection, thermal shutdown protection, control unit, and power MOSFET switches, requiring minimal external components and offering simple application — ideally suited for single-cell NiMH battery charging. Upon input power-up, CN3600 enters constant current charging mode, and the pin outputs a low level to indicate that charging is in progress. During the internal P-channel MOSFET on-time, the inductor current rises until it reaches the set peak current, at which point the P-channel MOSFET turns off and an N-channel MOSFET turns on, causing the inductor current to decrease and transferring the energy stored in the inductor to the output capacitor and battery. The P-channel MOSFET off-time is fixed at 2 microseconds. After the off-time expires, the N-channel MOSFET turns off and the P-channel MOSFET turns on, repeating this cycle. The battery voltage is monitored via the BAT pin. When the BAT pin voltage reaches 1.36V (typical), CN3600 enters trickle charge mode. In trickle charge mode, the peak inductor current is lower than that in constant current charging mode. An internal timer starts at the beginning of trickle charge mode; when the timer expires or the battery voltage reaches the maximum voltage (1.46V typical), the charging process terminates. In the charge termination state, the internal P-channel MOSFET turns off and no current flows to the battery, while the pin outputs a low level to indicate that charging is complete. When the BAT pin voltage drops to 1.339V (typical), CN3600 re-enters constant current charging mode and begins a new charge cycle. CN3600's switching frequency can reach 500KHz, enabling the use of compact inductors and capacitors. Additional features include peak inductor current selection via the Isel pin, battery overvoltage protection, and thermal shutdown protection.

Applications

• Standalone NiMH battery charger
• Automotive models
• Toys
• Devices using AA or AAA batteries

Key features

• Input voltage range: 2.7V to 6.5V
• Operating current: 320μA @ VIN = 5V
• Automatic charge current adjustment based on input power source load capability
• Compatible with solar panel power supply
• Switching frequency up to 500KHz
• Trickle charge mode ensures battery fully charged
• Selectable inductor peak current (ipeak)
• Charge termination at battery voltage 1.46V or via timer
• Auto-recharge function
• Battery overvoltage protection
• Chip overtemperature protection
• Two open-drain status indicator outputs
• Operating temperature range: -40℃ to 85℃
• eSOP-8 package
• Lead-free, RoHS compliant, halogen-free