The MC34671 is a cost-effective fully-integrated battery charger for Li-Ion or Li-Polymer batteries. The high input voltage, up to 28V, eliminates the input over-voltage-protection circuit required in handheld devices such as cell phones, Bluetooth accessories and MP3 players.
A typical charge cycle includes trickle, constant-current (CC) and constant-voltage (CV) charge modes. The CC-mode current is programmable up to 600mA with an external resistor. The voltage across the external resistor is also used to monitor the actual charge current. The constant voltage is fixed at 4.2V with 0.7% accuracy over a -20°C to 70°C temperature range. The trickle-mode current is preset to 20% of the CC-mode current when the battery voltage is lower than the trickle-mode threshold. The end-of-charge (EOC) current threshold is preset to 10% of the CC-mode current to save the board space and cost. A charge current thermal foldback feature limits the charge current when the IC internal temperature rises to a preset threshold. The MC34671 also protects the system with its input over-voltage protection (OVP) feature. In addition, the MC34671 has a 2.6V falling power-on-reset (POR) threshold, making it perfect to work with current limited power supplies. Three indication pins (PPR, CHG and FAST) can be simply interfaced to a microprocessor or LEDs. When no power supply is connected, or when disabled, the charger draws less than 1.0μA leakage current from the battery.