EA4021

EA4021 is a highly integrated 28V 1A single-cell lithium-ion battery linear charge management controller. The charging process consists of three stages: trickle charge, constant current charge, and constant voltage charge, requiring no external sense resistors, isolation diodes, or MOSFETs. Thermal feedback regulates the charge current to limit the die temperature during high-power operation or elevated ambient temperatures, maximizing the charge rate without the risk of overheating. The charge current is set via an external resistor. After the final cutoff voltage is reached and the charge current drops to 1/10 of the programmed value, EA4021 automatically terminates the charge cycle. If the battery voltage falls below the internal recharge threshold, charging restarts automatically. EA4021 features a built-in battery reverse polarity protection circuit — reversing the battery polarity will not damage the IC. EA4021 provides a CHRG indicator pin to indicate charging status and a FULL indicator pin to indicate charge completion; the two pins work together to indicate other fault conditions as well. EA4021 is a standalone linear lithium-ion battery charger with thermal regulation, requiring one external 1% precision resistor to set the charge current. A normal charge cycle begins when the voltage at the VIN pin exceeds the UVLO threshold. If the battery voltage is below V_TRKL, the device operates in trickle charge mode. The trickle charge current is 1/10 of the programmed value, effectively protecting the battery from damage and extending battery life. When the voltage at the BAT pin rises above V_TRKL, the charger enters constant current mode, where the charge current equals the programmed value. Once the BAT pin voltage reaches VFLOAT, the charger enters constant voltage mode and the charge current decreases. In constant voltage mode, the charge cycle ends once the charge current drops to 1/10 of the programmed value. After the charge cycle completes and charging stops, EA4021 continues to monitor the BAT voltage. Once the BAT voltage drops to 4.05V, it initiates a new charge cycle. EA4021 includes a soft-start circuit to reduce inrush current at the start of a charge cycle, protecting both the IC and battery. When the PROG pin is left floating, the charger enters shutdown mode. The PROG pin can also be used as a chip enable pin. EA4021 monitors the input voltage through an internal UVLO circuit. When the VIN voltage falls below the UVLO threshold, the IC halts charging and remains in output shutdown mode. When VIN rises above the UVLO threshold, the IC exits UVLO and resumes normal operation. The UVLO circuit has a built-in 200mV hysteresis. Additionally, to prevent reverse current through the power MOSFET, if VIN drops to within 50mV of the battery voltage, the UVLO circuit holds the IC in shutdown mode. The IC does not exit shutdown mode and resume normal operation until VIN rises to 200mV above the battery voltage. EA4021 monitors the VIN voltage through an internal OVLO circuit. When the VIN voltage exceeds the OVLO threshold, the IC halts charging and remains in output shutdown mode. When VIN drops below the OVLO threshold, the IC exits OVLO and resumes normal operation. The OVLO circuit has a built-in 400mV hysteresis. The EA4021 charging function can be manually disabled by pulling the CE pin low or disconnecting RPROG, and re-enabled by setting the CE pin HIGH or reconnecting RPROG. EA4021 features temperature monitoring to protect the battery from damage caused by charging at excessively high or low temperatures. Battery temperature sensing is implemented by monitoring the TEMP pin voltage, which is derived from a voltage divider formed by the NTC thermistor inside the battery and an external resistor. EA4021 compares the voltage VTEMP on the TEMP pin against the VLOW and V_HIGH threshold voltages, and terminates the charging process when VTEMP > V_HIGH or VTEMP < V_LOW. VLOW equals 5% of VIN, and V_HIGH equals 80% of VIN. This function is disabled when the TEMP pin is connected to GND or left floating. EA4021 features battery reverse polarity protection. When the battery is connected in reverse, EA4021 will not operate normally — no charge current flows, a fault condition is indicated, and the charge LED flashes once per second. When the battery is correctly connected, EA4021 automatically resumes normal charging operation.