DC788B Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 788B SINGLE CELL LI-ION BATTERY CHARGER WITH NTC LTC4061-4.4 DESCRIPTION Demonstration circuit 788B is a complete constant- vided for adding a thermistor for sensing battery current, constant-voltage battery charger for one temperature, shutting down the charger, monitoring Lithium-Ion cell that requires a higher float voltage of charge current and programming the minimum 4.375V. The LTC4061EDD-4.4 used on this demo cir- charge current level for termination (I ). An DETECT cuit features an internal P-Channel power MOSFET LED indicates when the charge current has dropped with a unique thermal feedback loop that reduces the below the minimum charge current termination level. output current under high ambient temperature The IC is available in a 10-Pin 3mm x 3mm DFN and/or high power dissipation conditions. This fea- thermally enhanced package featuring an exposed ture allows the charger to provide higher charge cur- bottom-side metal pad for soldering to the PC board. rents under normal conditions and still provide safe charging under abnormal conditions such as high ambient temperature, high input voltage or low bat- Design files for this circuit board are available. tery voltage. Call the LTC factory. Jumpers on the board allow charge currents from LTC is a trademark of Linear Technology Corporation 50mA to 1A to be programmed and several charge termination methods to be used. Terminals are pro- Table 1. Typical Specifications (25C) Input Voltage Range V 4.5 to 8V (upper range limited by PC board power IN dissipation) Input UnderVoltage Lockout 3.8V Output Float Voltage V (constant voltage mode) 4.375V 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 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 788B SINGLE CELL LI-ION BATTERY CHARGER WITH NTC OPERATION terminates the charge cycle when the charge cur- Demonstration circuit 788B allows three methods rent drops to a programmed threshold level after of charge termination which are selected using the battery has reached the constant voltage por- jumper JP1. In the lower Timer position, the tion of the charge cycle. Placing the jumper (JP1) charge cycle terminates at the end of the timer pe- in the middle position defeats the on board termi- riod as set by capacitor C2. The 3 hour timer is suf- nation thus allowing external user termination. ficient time 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 C 500mA 100mA 250mA 25mA LOW C/5 100mA 100mA 50mA 25mA The CHRG LED always indicates the presence of The current monitor terminal can be used to indi- charge current that is greater than the I cate charge current level at all times during the DETECT current level that is selected by the IDET jumper charge cycle with 1 Volt indicating 100% of the (JP4). The LED is on for charge current greater programmed current. This terminal can also be than IDET, regardless of the termination method used to program other charge currents by remov- used as set by jumper JP1. ing jumper JP3 and connecting an external pro- gramming resistor from the current monitor termi- When minimum charge current termination nal to ground. See data sheet for details. (I ) is used, the charge cycle ends when the DETECT charge current drops below the I level. The DETECT CHRG LED also goes off. 2