DC789A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 789 SINGLE CELL LI-ION BATTERY CHARGER WITH COMPARATOR LTC4062 DESCRIPTION Demonstration circuit 789 is a complete constant- for the comparator input. Terminals are provided for current, constant-voltage battery charger for one the comparator input and output, shutting down the Lithium-Ion cell and includes a comparator which can charger, monitoring charge current and programming be used to monitor battery voltage or other voltages. the minimum charge current level for termination The LTC4062EDD used on this demo circuit features (I ). Two LEDs are included, one indicates DETECT an internal P-Channel power MOSFET with a unique when the charge current has dropped below the thermal feedback loop that reduces the output current minimum charge current termination level and the under high ambient temperature and/or high power second indicates the comparator output state. dissipation conditions. This feature allows the charger The IC is available in a 10-Pin 3mm x 3mm DFN to provide higher charge currents under normal con- thermally enhanced package featuring an exposed ditions and still provide safe charging under abnormal bottom-side metal pad for soldering to the PC board. conditions such as high ambient temperature, high input voltage or low battery voltage. Design files for this circuit board are available. Call Jumpers on the board allow charge currents from the LTC factory. 50mA to 1A to be programmed and several charge termination methods to be used. A jumper also se- LTC is a trademark of Linear Technology Corporation lects either the battery voltage or an external voltage Table 1. Typical Specifications (25C) Input Voltage Range V 4.3 to 8V (upper range limited by PC board power IN dissipation) Input UnderVoltage Lockout 3.8V Output Float Voltage V (constant voltage mode) 4.2V 0.5% BAT Output Current I (constant current mode) From 50mA to 1A 8% (selected by jumpers) BAT Current Monitor Output 1V 5% Full Current Charge Termination Timer 3 Hours 10% Charge Termination Threshold Current (I ) 25mA, 50mA, 100mA 10% DETECT Comparator Threshold 2.910V 3% 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 789 SINGLE CELL LI-ION BATTERY CHARGER WITH COMPARATOR OPERATION terminates the charge cycle when the charge cur- Demonstration circuit 789 allows three methods of rent drops to a programmed threshold level after charge termination which are selected using jumper the battery has reached the constant voltage portion JP1. In the lower TIMER position, the charge cy- of the charge cycle. Placing the jumper (JP1) in the cle terminates at the end of the timer period as set middle position defeats the on board termination by capacitor C2. The 3 hour timer is sufficient time thus allowing external user termination. to fully charge a depleted battery when charging at a current level ranging from C/2 to 1C. The charge current and the termination current are selected using a combination of jumpers JP2, JP3 The upper ITERM position selects minimum and JP4. (See table 2) charge current termination (I ). This method DETECT Table 2. Jumper Positions for Charge Current and Termination Current. IDET JUMPER (JP4) 100MA C / 10 ICHG-1 ICHG-2 Charge Current Idetect Current Charge Current Idetect Current (JP3) (JP2) C 1A 100mA 500mA 50mA HIGH C / 5 200mA 100mA 100mA 50mA LOW C 500mA 100mA 250mA 25mA C/5 100mA 100mA 50mA 25mA The CHRG LED always indicates the presence of programmed current. This terminal can also be charge current that is greater than the I cur- used to program other charge currents by removing DETECT rent level that is selected by the IDET jumper (JP4). jumper JP3 and connecting an external program- The LED is on for charge current greater than IDET, ming resistor from the CURRENT MONITOR termi- regardless of the termination method used as set by nal to ground. jumper JP1. The COMP IN terminal is connected to the com- When minimum charge current termination parators non-inverting input when selected using (I ) is used, the charge cycle ends when the the COMP jumper (JP5 upper position) and COMP DETECT Charge current drops below the I level. The OUT is the open drain comparator output. The DETECT CHRG LED also goes off. comparator output also drives the COMP LED. The comparator monitors the battery voltage when The CURRENT MONITOR terminal can be used to jumper (JP5) is in the BAT (lower) position. See indicate charge current level at all times during the data sheet for details. charge cycle with 1 Volt indicating 100% of the 2