DEMO CIRCUIT 1284A QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1284A QUICK START GUIDE USB Compatible Switching Power Manager/Li-Ion Charger LTC4098EPDC: USB Compatible with Overvoltage Protection Switching Power Manager/Li-Ion Charger LTC4098EPDC with Overvoltage Protection DESCRIPTION Demonstration Circuit 1284A is a high efficiency USB Design files for this circuit board are available. Call Power Manager, Li-Ion battery charger and HV buck the LTC factory. regulator battery tracking controller, using the L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy LTC 4098EPDC, and HV, high efficiency buck regula- Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode tor, the LT3480EDD. Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names The LTC4098EPDC is available in the ultra-thin may be trademarks of the companies that manufacture the products. (0.55mm) 20-lead 3mmx4mm QFN surface mount package. PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VUSB Bus input voltage range Input disabled for VUSB 6V 4.35 30 V HVIN High voltage input voltage range 8 38 V Adaptor 5V adaptor input voltage range 4.5 5.5 V VOUT Output voltage range Range is mode and load dependant 3.5 4.7 V BAT Battery float voltage Constant voltage mode 4.2 V I Output charge current Constant current mode 0.5 1.5 A BAT OPERATING PRINCIPLES The LTC4098 is a Li-Ion battery charger/power manager The current that the charger supplies to the battery, for that can control a preregulator for the charger input volt- non-USB applications, is also programmable via the age. This allows for minimal power dissipation in the PROG pin resistance, up to 1A. charger. The current available at VOUT is preferentially supplied to The LTC4098 also contains an integrated buck regulator any system load connected to VOUT, the remaining cur- that can provide the preregulation function, called Bat- rent is supplied to the battery charger up to the amount Track from a 5V input supply, usually a USB port. set by the PROG resistor. If the input supply is a USB port, then the load presented The current available at VOUT is the USB current as ne- to the USB port can be programmed to comply with the gotiated with the USB host (I ) times the transformer USB USB standards. This load can be set to 100mA, or action of the VOUT switching regulator: 500mA, as negotiated with the USB host, and is pro- VUSB I * * (buck regulator) = I grammed using the D 2-0 inputs and the CLPROG pin USB VOUT VOUT resistance. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1284A USB Compatible Switching Power Manager/Li-Ion Charger with Overvoltage Protection LTC4098EPDC If the battery voltage is 3.6V, and VBUS is 5V, and the the LT3480 is via the Vc pin, allowing the LT3480 to Bat- negotiated USB current is 500mA, then the current avail- Track, and hence minimize the dissipation in the battery able at VOUT is approximately 590mA. This will be sup- charger. The output of the LT3480 is used preferentially plied to any VOUT loads before the battery charger. over the USB input by turning off the internal buck regu- lator and turning on a MOSFET to connect the output of The LTC4098 also has an ideal diode function allows the the LT3480 to the LTC4098 V pin. The presence of OUT maximum energy to be extracted from the battery, by the LT3480 output is sensed via the WALL pin on the minimizing the voltage drop from BAT to VOUT. The LTC4098, and the MOSFET gate is driven by the ACPR ideal diode function supports an optional external pin. By connecting the output of the LT3480 to the MOSFET for excellent efficiency at higher battery cur- VOUT pin, the LT3480 can supply both full battery rents. charge current and full load current, without concern USB voltages higher than 6V will activate an overvoltage about meeting the USB maximum power restrictions. protect function on the LTC4098, which uses an external The WALL pin detects the presence of an appropriate MOSFET to protect against application dependent input voltage to operate the LTC4980, and this could be sup- overvoltages. This is achieved by simply selecting an plied by an external adaptor, so that no additional regula- external MOSFET with the appropriate BV . DSS tor is required by the LTC4098. However, this solution If it is desired to operate the LTC4098 from voltages will not allow the Bat-Track function to be implemented, higher than 6V, an external HV regulator is needed. The and consequently the dissipation of the battery charger DC1284A board uses an LT3480, high frequency, HV, will increase. buck regulator. The interface between the LTC4098 and 2