Part # Application Notes Mobile STBC08 AN2407 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: 800mA standalone linear Li-Ion battery charger with thermal regulation


Part Details:

AN2407 Application note 800mA standalone linear Li-Ion battery charger with thermal regulation Introduction One way to minimize the size and complexity of a battery charger is to use a linear-type charger. The linear charger drops the AC adapter voltage down to the battery voltage. The number of external components is low: linear chargers require input and output bypass capacitors, and sometimes need an external pass transistor, and resistors for setting voltage and current limits. The main pitfall of a linear charger is power dissipation. The charger simply drops the AC adapter voltage down to the battery voltage. In the case of an 800mA charger, a 5V±10% regulated AC adapter voltage, and battery voltage that varies between 4.2V and 2.5V, the power dissipation can range from 0.6W to 2.0W. This type of charger is simpler than the switch-mode type, mainly because the passive LC filter is not required. It dissipates the most power when the battery voltage is at its minimum, since the difference between the fixed input voltage and the battery voltage is greatest during this condition. Application diagram September 2006 Rev 2 1/14 www.st.com Contents AN2407 Contents 1 STBC08 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Stability considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Board layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 External components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 Automatic recharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7 CHRG and Power-on status output pins . . . . . . . . . . . . . . . . . . . . . . . . . 9 8 USB and wall adapter power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9 Charge current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.1 Programming charge current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.2 Maximum charge current in temperature . . . . . . . . . . . . . . . . . . . . . . . . . 11 Appendix A Board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2/14 AN2407 STBC08 description 1 STBC08 description The STBC08 is a constant current/constant voltage charger for single cell Li-Ion battery. No external sense resistor or blocking diode is required and its MLPD 3x3mm² 6L package make it ideally suited for portable applications. The STBC08 is designed to comply with USB power specifications. An internal block regulates the current when the junction temperature increases in order to protect the device when it operates in high power or high ambient temperature. The maximum power dissipation occurs when VBAT is 2.9V with the maximum charge current. The charge voltage is fixed at 4.2V, and the charge current limitation can be programmed using a single resistor connected between pins PROG and GND. The charge cycle finishes when the current flowing to the battery is 1/10 of the programmed value. If the external adaptor is removed, the STBC08 switches off and only 2µA can flow from the battery to the device. The device can be put into Shutdown Mode, reducing the supply current to 25µA. Figure 1.


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Application Notes Mobile STBC08 AN2407.pdf Datasheet