DC672A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 672 LI-ION CHARGER IN DFN 3X3 LTC4058-4.2 DESCRIPTION Demonstration circuit 672 is a single cell Li-Ion age is present to allow battery charging. The CHARGE charger in a DFN3x3. Charge rates as high as 800mA terminal is pulled low every time charge current is can be achieved due to the LTC 4058 packages ex- supplied to the output. The status of the ACPR and cellent thermal performance and internal die tempera- CHARGE outputs of the LTC4058 are also indicated ture control loop that prevents excessive PCB heating visually by two LEDs. under worst-case conditions. The user is provided with a control jumper to enable the charger. An en- Design files for this circuit board are available. Call able terminal is also provided to simplify wiring the the LTC factory. demo board into a system. The user is also provided with 3 status outputs. The PROG terminal outputs a LTC is a trademark of Linear Technology Corporation voltage proportional to the charge current. The ACPR terminal is pulled low whenever sufficient input volt- Table 1. Performance Summary PARAMETER CONDITION VALUE Input Voltage 4.2-6.3V Iout Vin=5V, Vbat=3.6V 800mA +- 7% Float voltage Vin =5V 4.20v+-1% Trickle Charge threshold V = 5V 2.9V +-0.1V IN C/10 detection V =5V Vbat=4.2 65mA-95mA IN Recharge threshold Vin 5V Vfloat 60mV Vfloat-150mV OPERATING PRINCIPLES Demo 672 is a simple single cell Li-Ion charger. The reaches 2.9V whereupon full charge current is ap- circuit features the LTC4058-4.2 charger IC. This plied. In the event that full charge current would re- charger implements a constant die temperature, con- sult in excessive IC temperature, a die temperature stant current, and constant voltage charge scheme. control loop backs off the charge current to maintain Charge termination occurs when the charge rate falls a reasonable PC board temperature. Two LEDs are to beneath 10% of the programmed charge current. provided for status indication. A charge LED is pro- A topping charge will be applied if the cell voltage vided that illuminates every time the charger is charg- falls to 4.05V to insure long-term charge mainte- ing the battery, and an AC power LED is provided to nance. Deeply discharged cells are conditioned with indicate that the part is out of under-voltage lockout. a low C/10 trickle current until the cell voltage The peak charge current is 800mA. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 672 LI-ION CHARGER IN DFN 3X3 QUICK START PROCEDURE Demonstration circuit 672 is easy to set up to evalu- iron and the charge current will increase. This ate the performance of the LTC4058-4.2. Refer to 0 demonstrates the constant die temperature oper- for proper measurement equipment setup and follow ating mode. the procedure below: 5. Continue to increase the battery voltage. Note that 1. Connect input power supply, meters and output as the voltage drop across the LTC4058 decreases, load as shown in figure 1. the constant die temperature loop is no longer ac- tive and the charge current is the programmed 2. Set the battery simulator voltage to zero, slowly charge current of 800mA raise the input voltage. When the supply voltage exceeds 3.9V the charger should activate and the 6. Continue to increase the battery voltage. As the charge LED will illuminate. battery voltage approaches the float voltage of 4.2V the charge current will begin to drop. Note that as NOTE: Make sure that the input voltage does not ex- the charge current drops to 10% of the pro- ceed 6.3V. grammed current the charger terminates. Charge 3. Note that so long as the battery voltage is under current falls to 0 and the charge LED extinguishes. the Trickle Charge threshold of 2.9V the charge 7. Now slowly decrease the battery voltage to simu- current is 10% of the selected charge current or late a long term self-discharge of the battery. Note approximately 80mA. that as the battery voltage drops to 4.10V that an- 4. Increase the battery voltage to about 3V and note other charge cycle is initiated. that the charge current has increased beyond the 8. Place the enable jumper in the OFF position. Note trickle charge current. Verify that the LTC4058-4.2 that the battery current draw is extremely low (ap- thermal loop is working by touching a soldering prox 1uA). Also note that the supply current draw iron to the PCB to heat up the LTC4058 and note is low (approx 20uA). that the charge current decreases. Remove the 2