QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1061A LINEAR LI-ION BATTERY CHARGER WITH DUAL SYNCHRONOUS BUCK REGULATOR LTC3552 Demonstration circuit 1061A is a complete sin- and pins on the board allow easy hookup to an gle cell Lithium-Ion battery charger and two input supply and battery or battery simulator. synchronous buck voltage regulators with ad- The high switching frequency of the voltage justable output voltages. Operating at a fre- regulators allow tiny LC components to be used quency of 2.25MHz, the regulators can be pow- and the 16-Pin 5mm x 3mm DFN thermally en- ered from either the Li-Ion battery or from the hanced package with the metal backside allow AC adapter selected by a jumper. the linear charger to provide up to 950mA of This demonstration circuit allows the user to charge current in addition to the regulators out- quickly evaluate the LTC3552 performance. In- put current. The charge current on this board is set for 600mA. dividual jumpers are provided for shutting down the charger and/or each of the switching regula- Design files for this circuit board are available. tors. Jumpers also allow for selecting several Call the LTC factory. regulator output voltages and the mode of op- LTC and Burst Mode are trademarks of Linear Technol- eration (Pulse Skip or Burst). LEDs indicate ogy Corporation charger information (input power and charge) Table 1. Typical Specifications (25C) Input Voltage Range V (Buck regulators powered from Battery) 4.25V to 6.5V IN Input Voltage Range V (Buck regulators powered from V ) 2.5V to 5.5V IN IN Charger Output Float Voltage, V (constant voltage mode) 4.2V 0.5% BAT Output Current, I (constant current mode) 600mA 6% BAT Current Monitor Output 1V 2.5% Full Current Charge Termination Current Threshold 40mA 10% C/x Output Indication Level (CHRG) 40mA 10% VOUT1 Regulator 1 Output Voltages 1.2V, 1.5V, 1.8V (100mA load) 2.5% VOUT1 Ripple Voltage - skip mode (300mA load) 10mV p-p VOUT1 Ripple Voltage - Burst mode (1mA load) 45mV p-p Regulator 1 Maximum Output Current 800mA VOUT2 Regulator 2 Output Voltages 2.5V, 3.3V (100mA load) 2.5% VOUT2 Ripple Voltage Skip mode (100mA load) 4mV p-p VOUT2 Ripple Voltage Burst mode (1mA load) 20mV p-p Regulator 2 Maximum Output Current 400mA 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1061A LINEAR LI-ION BATTERY CHARGER WITH DUAL SYNCHRONOUS BUCK REGULATOR be used to program different charge current The battery charger portion of demonstration and also measure the charge current anytime circuit 1061A uses a constant-current/constant in the charge cycle. The PROG pin voltage is voltage charge algorithm with minimum charge directly proportional to the charge current current termination. The battery float voltage is where one Volt is equal to full programmed fixed at 4.2V and the charge current is pro- current. grammed for 600mA, although other charge currents up to 950mA can be programmed by The 2.25MHz synchronous buck regulators replacing the program resistor (R4) with a suit- have jumpers to select output voltages of 1.2V, able value. Either a leaded resistor, from 1.5V, or 1.8V at 800mA for VOUT1 and output PROG to GND, or a 0402 surface mount resis- voltages of 2.5V or 3.3V at 400mA for VOUT2. tor can be used. Individual jumpers are also provided for low quiescent current shutdown and for either Power and Charge LEDs indicate charger pulse skip or Burst mode operation. Both regu- status. The Power LED indicates the input lators operate in the continuous mode at high voltage is greater than the undervoltage lock- current and automatically switch to the se- out threshold level. lected mode at low current levels. Burst mode The Charge LED indicates a charge cycle is in provides higher efficiency at low load current. progress. The LED is ON when the charger is The input power for the regulators can be from in the trickle current, or the constant voltage either the VIN terminal or from the battery, se- portion of the charge cycle when the charge lected by a jumper. Note that when the regula- current is dropping. When the charge current tors are powered from VIN, the maximum input drops below the charge termination current voltage is limited to 5.5V. Normally, a Li-Ion threshold level of 40mA, the LED goes off and battery would be connected to the BAT pin, al- the charge cycle ends. though the buck regulators can be operated If the battery voltage drops approximately without a battery. When no battery is present, 100mV from the float voltage, after the charge some additional capacitance on the BAT pin cycle has ended, a recharge cycle will begin. may be needed. The charger can be shut down by pullling the EN terminal to VIN. The PROG terminal can 2