DEMO CIRCUIT DC1303A QUICK START GUIDE LTC4098EPDC: USB Compatible Switching Power Manager/Li-Ion Charger with Overvoltage Protection DESCRIPTION

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1 Demonstration Circuit A is a high efficiency USB Power/LiIon battery manager plus a HV regulator battery tracking controller. The LTC98EPDC is available in a pin (mm mm.mm) UTQFN surface mount package. DEMO CIRCUIT DCA QUICK START GUIDE LTC98EPDC: USB Compatible Switching Power Manager/LiIon Charger with Overvoltage Protection DESCRIPTION L, LTC, LTM, LT, Burst Mode, OPTILOOP, OverTheTop and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, CLoad, DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, μmodule, Micropower SwitcherCAD, Multimode Dimming, No Latency ΔΣ, No Latency DeltaSigma, No R SENSE, Operational Filter, PanelProtect, PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. PERFORMANCE SUMMARY Specifications are at T A = C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V BUS Bus Input Voltage Range Input disabled from 6V V.. V V OUT Output Voltage Range Range is mode and load dependant.. V V BAT Output Float Voltage Constant voltage mode. V I BAT Output Charge Current Constant current mode. A OPERATING PRINCIPLES The LTC98EPDC is a full featured USB power manager and LiIon battery charger, with reacharound. The BatTrack battery charger preregulator ensures the charger operates at the highest possible efficiency. The LTC98EPDC is composed of functional blocks, all working together: USB Power Manager, Preregulator, Battery Charger, Ideal Diode, and OverVoltage Protection. USB Power Manager The USB Power Manager is used to manage the load that the LTC98EPDC system presents to the USB interface. The load current can be programmed by changing the CLPROG resistor (R), and by setting the operating mode to X, X or x, with the [dd] inputs. Please note that the charger on/off is also controlled by the [dd] inputs. The USB Power Manager also uses the WALL input to determine that power is being supplied directly to and shuts off the internal preregulator, minimizing the load on the USB input. PreRegulator The preregulator is a high efficiency buck regulator that produces a voltage at = BAT.V. The voltage at is input to the battery charger, greatly reducing dissipation in the charger. The preregulator also monitors the WALL pin, and when the voltage is higher than.v, it shuts off. When the voltage on the Wall pin is higher than.v, the /ACPR and VC pins are also active. The /ACPR pin activates the gate of an Nchannel MOSFET allowing a separate HV Buck Regulator to supply. The VC pin implements the BatTrack function for the HV Buck Regulator, also known as reacharound, enabling the same high efficiency battery charger operation with an external HV buck regulator. Battery Charger The battery charger operates in constant current mode, until the battery voltage rises to approximately the FLOAT voltage, of.v, and then the charger switches to constant voltage mode. The charge current is programmed by the PROG (R) resistor, and has been set to ma, on DCA,

2 with a.kω resistor. The battery charger implements trickle charging, for initial battery voltages less than.v. It also implements a charge termination timeout of hours, and a bad cell charging timeout of minutes. An input is used to determine if the battery temperature is suitable for charging, too hot or too cold. The state of charge, as well as any faults, is signaled with the CHRG pin. Ideal Diode The Ideal Diode block is composed of an internal Ideal Diode implemented with an on die MOSFET, as well as a MOSFET gate driver that allows the use of a parallel external MOSFET. When the voltage on drops more than mv below the voltage at BAT, the Ideal Diode becomes active. This will happen when there is neither a VBUS nor external HV buck to supply, or the load on exceeds the power available from those sources. OverVoltage Protection The overvoltage protection is composed of a sense pin, OVSENSE, and an OVP MOSFET gate drive, OVGATE. If the voltage on OVSENS is less than 6V, OVGATE is driven above VBUS, by an internal charge pump, to allow the use of a low cost Nchannel MOSFET. If the voltage on OVSENS exceeds 6V, the charge pump is shut off and pulled to ground. This in turn shuts off the external OVP MOSFET. Although the OVP is usually shown protecting the VBUS connection, it could also be used to protect the connection to an external regulator. APPLICATIONS The parasitic inductance in some USB cables may cause the VUSB voltage to overshoot at plug in. The OVGATE signal provides a slow turn on of Q, the OVP MOSFET. This slow turn on, in turn limits the inrush current into C, allowing the use of a capacitor that exceeds the nominal USB specification. R, the OVSENS current limit resistor must be an 6, or larger resistor. OVSENS is clamped at 6V, so for a V input, the dissipation in the resistor is V /6.kΩ = 9mW. An 6 resistor is rated at mw of continuous dissipation. The battery charger must see a low impedance to ground, which is case when a battery is attached. In the event that a battery emulator is being used, or the impedance to ground is above Ω, the circuit of C and R9 is recommended. Without this circuit there will be approximately ma of 8kHz ac current in the USB input. While this will not damage the LTC98EPDC, nor cause incorrect operation, it may produce voltage waveforms that are undesireable. If this is the case the network of C and R9 will resolve this issue. The HV buck interface connector is intended for use with specific demonstration boards, that contain HV buck regulators tested to work with the LTC98EPDC. ASSEMBLY TEST PROCEDURE Using short twisted pair leads for any power connections, with all loads and power supplies off, refer to Figures & for the proper measurement and equipment setup. A companion HV Buck demo board is required for this check out procedure. The DC9 (LT8) board is recommended, and will be used for the following procedure. Please refer to the DC9 Quick Start Guide for further information. Follow the procedure below:. Select input from VUSB: Set WALL jumper (DC9, JP) to V ADAPTOR. Ensure that PS is off. Since PS is off and the voltage input is set to V ADAPTOR, no voltage will be sourced to from the DC9 board. Thus the only source of energy is the USB voltage input.. Set PS to V, and PS to.6v. Observe (VM).6V, I(VUSB) (AM) ma, (CLPROG) (VM7) V. The default operating mode is ma USB input current limit, and the

3 battery charger on. The battery charger is programmed for ma of charge current by R (k), so the charge is trying to source more curren from the USB input than the USB input current limit. So Vout collapses down to approximately the battery voltage.. Set D (JP) to. Observe (VM).9V, I(VUSB) (AM) ma, V(CLPROG) (VM7).V and V(PROG) (VM6) V. By setting D to, the USB input current limit has been increased to X (ma) mode. The USB input can now supply the battery with ma, so rises to V(BAT).V.. Set D (JP) to and D (JP) to. Observe (VM).9V, I(VUSB) (AM) ma, V(CLPROG) (VM7).6V and V(PROG) (VM6) V. The USB input current limit is now in X (A) mode, so the USB input current limit current sense voltage, V(CLPROG), is at about half its threshold (.V) value. But the charge current sense is still V, as the charger is delivering the full programmed charge current.. Set PS to V, and Ld to A. Observe (VM).6V and V(,BAT) mv. With voltage on USB now V, there is no source of energy so collapses until the ideal diode comes on, and the battery holds up. 6. Set Ld to A. Observe (VM).6V and V(,BAT) mv. Set Ld to A. The Rds(on) of the external ideal diode MOSFET is approximate mω, so at A, the voltage drop in the ideal diode is approximately mv. 7. Set PS to V. Set (JP) to EXT. Does the Battery Charging LED blink? Set (JP) to INT. Setting the (JP) jumper to EXT, uses the temperature sense in the battery pack. There is no battery pack connected, so this connection is open. This is the same as if the where high impedance indicating a battery too cold fault. 8. Set WALL (DC9, JP) to HVBUCK, and SYNC (DC9, JP) to PWM/SYNC. Increase PS from V to 8V. Observe (VM).9V and V(PROG) (VM6) V. The LTC8EDD HV buck regulator on the DC9 board is now providing energy for the charger. The LTC98EPDC on the DCA board is controlling the output voltage to provide the Bat Track function, and minimize dissipation in the charger. 9. Set Ld to A. Observe (VM).9V and V(PROG) (VM6) V. The LTC8EDD can supply up to A of load current. The DCA board is currently drawing.a, ma for the charger, and A into Ld.. Set PS to 8V. Observe (VM) and V(PROG) (VM6). The LTC8EDD can supply up to A of load current. The DCA board is currently drawing.a, ma for the charger, and A into Ld.. Set Ld to A. Set WALL (DC9, JP) to V ADAPTOR and PS to V. Observe (VM) V and V(PROG) (VM6) V. The charger current is now being supplied by the V ADAPTOR, but the voltage is fixed, as the LTC98EPDC cannot control this voltage. This means that the dissipation will be higher than when operating the LTC98EPDC from the USB or HV buck inputs.. Set D (JP) to. Does BATTERY CHARGING LED go out? This turns the battery charger off.

4 PS VV supply A AM VM PS V6V supply A AM VM D D D VM AM Ld VV A PS V6V supply A AM VM AM VM.6Ω PS VV supply A VM7 VM6 Note: All connections from equipment should be Kelvin connected directly to the Board PINS which they are connected to on this diagram and any input, or output, leads should be twisted pair Figure. Proper Measurement Equipment Setup for DCA VIN Figure. Measuring Input or Output Ripple

5 J VUSB D D ID TP D TP D TP ID MINIB USB BIAS E E JP D JP D JP D PROG E E6 CLPROG C uf 6 % 6.V R. R.k R 6.k 6 C.uF 6V Q Si6BDS TP OVGATE Leakage current must be < na JP R7 k INPUT CURRENT LIMIT SETTINGS CURRENT CHARGER D D D LIMIT STATUS ma (X) ON A (X) ON ma (X) ON ua (SUSP) OFF ma (X) OFF A (X) OFF ma (X) OFF.mA (SUSP) OFF L.uH LPS8MLC Unless noted: Resistors: Ohms,, %, /6W Capacitors: uf,, %, V R8 EXT INT R6 C uf 8 % 6.V R9. C uf % 6.V 6 R. R. SQT8FDRA HV BUCK INTERFACE D BATTERY CHARGING Green.V.V.A E E CHRG R BATSENS E8 BAT VFLOAT =.V.A E7 J BAT DFPDSA OPT VUSB E R k C uf 8 % 6.V LTC98EPDC U VBUS OVGATE VC ACPR 9 OVSENS WALL 8 BIAS SW Leakage currrent must be < na IDGATE D 6 CHRG D 7 D BATSENS PROG CLPROG BAT Q SiDS J 6 VC/TRACK ACPR PG WALL SYNC SHDN DVCC ILIM SDA HVOK/INIT SCL HVIN R k V.V, Nonoperating Fault Tolerance to V Continous, 6V Transient. E R.k E E9 Figure. DCA Schematic

6 6 Figure. DCA BOM