DEMO CIRCUIT DC1303A QUICK START GUIDE LTC4098EPDC: USB Compatible Switching Power Manager/Li-Ion Charger with Overvoltage Protection DESCRIPTION L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered Demonstration Circuit 1303A is a high efficiency USB trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy Power/Li-Ion battery manager plus a HV regulator bat- Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE tery tracking controller. The LTC4098EPDC is avail- PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names able in a 20-pin (3mm 4mm 0.55mm) UTQFN sur- may be trademarks of the companies that manufacture the products. face mount package. PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Bus Input Voltage Range Input disabled from 6V30V 4.35 5.5 V BUS V Output Voltage Range Range is mode and load dependant 3.5 5.5 V OUT V Output Float Voltage Constant voltage mode 4.2 V BAT I Output Charge Current Constant current mode 0.5 1 A BAT Pre-Regulator OPERATING PRINCIPLES The pre-regulator is a high efficiency buck regulator The LTC4098EPDC is a full featured USB power man- that produces a voltage at VOUT = BAT + 0.3V. The ager and Li-Ion battery charger, with reacharound. voltage at VOUT is input to the battery charger, greatly The Bat-Track battery charger pre-regulator ensures reducing dissipation in the charger. the charger operates at the highest possible efficiency. The pre-regulator also monitors the WALL pin, and The LTC4098EPDC is composed of 5 functional blocks, when the voltage is higher than 4.3V, it shuts off. all working together: USB Power Manager, Pre- When the voltage on the Wall pin is higher than 4.3V, regulator, Battery Charger, Ideal Diode, and OverVolt- the /ACPR and VC pins are also active. The /ACPR pin age Protection. activates the gate of an N-channel MOSFET allowing a separate HV Buck Regulator to supply VOUT. The VC USB Power Manager pin implements the Bat-Track function for the HV Buck The USB Power Manager is used to manage the load Regulator, also known as reacharound, enabling the that the LTC4098EPDC system presents to the USB same high efficiency battery charger operation with an interface. The load current can be programmed by external HV buck regulator. changing the CLPROG resistor (R5), and by setting the operating mode to 1X, 5X or 10x, with the d2-d0 in- Battery Charger puts. The battery charger operates in constant current mode, Please note that the charger on/off is also controlled by until the battery voltage rises to approximately the the d2-d0 inputs. FLOAT voltage, of 4.2V, and then the charger switches The USB Power Manager also uses the WALL input to constant voltage mode. to determine that power is being supplied directly to VOUT and shuts off the internal preregulator, minimiz- The charge current is programmed by the PROG (R4) ing the load on the USB input. resistor, and has been set to 500mA, on DC1303A, R2, the OVSENS current limit resistor must be an with a 2.00k resistor. The battery charger imple- 0603, or larger resistor. OVSENS is clamped at 6V, so ments trickle charging, for initial battery voltages less for a 30V input, the dissipation in the resistor is than 3.0V. It also implements a charge termination 2 24V /6.04k = 95mW. An 0603 resistor is rated at timeout of 4 hours, and a bad cell charging timeout of 100mW of continuous dissipation. 30 minutes. An NTC input is used to determine if the The battery charger must see a low impedance to battery temperature is suitable for charging, too hot or ground, which is case when a battery is attached. In too cold. the event that a battery emulator is being used, or the The state of charge, as well as any faults, is signaled impedance to ground is above 1, the circuit of C4 with the CHRG pin. and R9-11 is recommended. Without this circuit there will be approximately 100ma of 20-80kHz ac current in Ideal Diode the USB input. While this will not damage the The Ideal Diode block is composed of an internal Ideal LTC4098EPDC, nor cause incorrect operation, it may Diode implemented with an on die MOSFET, as well as produce voltage waveforms that are undesireable. If a MOSFET gate driver that allows the use of a parallel this is the case the network of C4 and R9-11 will re- external MOSFET. solve this issue. The HV buck interface connector is intended for use When the voltage on VOUT drops more than 30mV with specific demonstration boards, that contain HV below the voltage at BAT, the Ideal Diode becomes buck regulators tested to work with the LTC4098EPDC. active. This will happen when there is neither a VBUS nor external HV buck to supply VOUT, or the load on ASSEMBLY TEST PROCEDURE VOUT exceeds the power available from those sources. Using short twisted pair leads for any power con- OverVoltage Protection nections, with all loads and power supplies off, refer The overvoltage protection is composed of a sense pin, to Figures 1 & 2 for the proper measurement and OVSENSE, and an OVP MOSFET gate drive, OVGATE. equipment setup. If the voltage on OVSENS is less than 6V, OVGATE is A companion HV Buck demo board is required for driven above VBUS, by an internal charge pump, to this check out procedure. The DC1394 (LT3480) allow the use of a low cost N-channel MOSFET. board is recommended, and will be used for the fol- If the voltage on OVSENS exceeds 6V, the charge lowing procedure. Please refer to the DC1394 Quick pump is shut off and pulled to ground. This in turn Start Guide for further information. shuts off the external OVP MOSFET. Follow the procedure below: Although the OVP is usually shown protecting the 1. Select input from VUSB: Set WALL jumper VBUS connection, it could also be used to protect the (DC1394, JP3) to 5V ADAPTOR. Ensure that VOUT connection to an external regulator. PS3 is off. Since PS3 is off and the voltage in- put is set to 5V ADAPTOR, no voltage will be sourced to VOUT from the DC1394 board. Thus APPLICATIONS the only source of energy is the USB voltage in- put. The parasitic inductance in some USB cables may cause the VUSB voltage to overshoot at plug in. 2. Set PS1 to 5V, and PS4 to 3.6V. Observe VOUT The OVGATE signal provides a slow turn on of Q1, the (VM4) 3.6V, I(VUSB) (AM1)100mA, OVP MOSFET. This slow turn on, in turn limits the (CLPROG) (VM7) 1V. The default operating inrush current into C2, allowing the use of a capacitor mode is 100mA USB input current limit, and the that exceeds the nominal USB specification. 2