DC370A-A Analog Devices

Quick Start Manual For Linear Technology Demo board DC370A-A (4.1V) and DC370A-B (4.2V) LTC1734 Linear Battery Charger for One Li-Ion Cell at 4.1V or 4.2V Demonstration board DC370A is a constant-current/constant- voltage battery charger designed to charge one Lithium-Ion cell. This demoboard features a preset charge voltage (1%) where the charge current can be easily programmed and monitored allowing for easy interface with a CPU or other circuitry providing charge termination. The LTC1734 used on this demoboard drives an inexpensive PNP transistor in a linear regulator configuration that provides up to 700mA of charge current. The IC and the pass transistor are available in tiny 5 and 6-pin SOT 23 packages which reduces the total circuit area to less than 0.08 square inches, although additional pc-board copper area is needed for heat dissipation. Other Features include Preset float voltages of 4.1 & 4.2V 1% 700mA Constant Current (can be programmed for other charge currents ranging from 100mA to 700mA) Monitor charge current using the Program pin No isolation diode required No sense resistor required Manual Shutdown Low battery drain current when input supply is removed Typical Demo Board Specifications Input Voltage Range (V ) 4.7V to 7V (upper range limited by pc board IN dissipation) Output Voltage (V ) in constant voltage BAT mode 4.1 1% for DC370A-A and 4.2V 1% for DC370A-B Output Current (I ) in constant BAT current mode 700mA 10% Program pin voltage at full charge current 1.5V 5% Battery Drain Current with V Removed <1A IN Test Equipment Required for Demo Board Evaluation Lab Power supply for input power 0 to 7V 1A Digital voltmeter for measuring input voltage (V 3-1/2 digits IN) Digital voltmeter for measuring battery voltage (V 4-1/2 digits, resolution to 1mV BAT) Digital voltmeter for measuring program pin voltage 3-1/2 digits, resolution to 1mV Digital voltmeter for measuring voltage across 3-1/2 digits current sense resistor Li-Ion cell or *Battery Simulator 4.1 or 4.2V Rechargeable Li-Ion Cell *Battery Simulator consists of Power supply with coarse and fine 0 to 5V 2A output voltage adjust controls 1 Power resistor (preload for power supply) 2 10W Current sense resistor for measuring charge current (I BAT) 0.1 1% 1W Current sense resistor for measuring battery drain current 1k 1% .5W Demoboard Evaluation Begin by assuring that the SHDN jumper (JP1) near the bottom of the demo board is installed. Referring to the setup diagram, connect the input power supply to the +V and Ground pins of IN the demo board (power supply set for 0V). Connect the battery simulator (power supply also set to 0V) to the BATT and GND pins, with the 0.1 current sense resistor in the charge path as shown in the setup diagram. The battery simulator consists of an adjustable power supply and a 2 ohm 10 Watt resistor load in parallel with the power supply output. Connect the digital voltmeters to measure charger input voltage V , charger voltage V , program pin voltage IN BAT V , and charge current I . PROG BAT Undervoltage Lockout - Start the demoboard evaluation by increasing the input power supply to approximately 4.0V (battery simulator power supply set for 0V). The charger output voltage and charge current should be 0. The charger is off due to the undervoltage lockout feature. Constant Current - Set the battery simulator power supply (V ) to approximately 2.6V, and BAT the input power supply to approximately 5.0V. The constant current portion of the charge cycle will immediately begin resulting in approximately 700mA of current flowing into the battery simulator, indicated by a reading of 70mV on the charge current DVM. This is the constant current portion of the charge cycle. V Verification - With the 700mA charge current flowing into the battery simulator, measure PROG the program pin voltage V . This voltage is proportional to charge current with 1.5V PROG indicating full programmed current. 2