DC567A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC567 USB BATTERY CHARGER LTC4410/LTC4053 DESCRIPTION Demonstration circuit DC567 shows how to use the Design files for this circuit board are available. LTC 4410 USB power manager IC in conjunction with Call the LTC factory. a battery charger IC, in this case the LTC4053, to LTC is a registered trademark of Linear Technology Corporation charge a battery from the USB cable. OPERATING PRINCIPLES DC567 achieves USB compliant battery charging by PCB temperatures. USB compliance is achieved by measuring the current to the USB application circuit the LTC4410, which measures the current flowing and reducing the charging current in order to hold the from the USB power input into the application load input current within the USB specification. and backs off the charge current in a 1:1 ratio to Connected to the demo board will be a single Li-Ion maintain compliant input current. The LTC4410 also cell, a source of charging power and an application provides power path management and in the event load. Battery charging is controlled by the LTC4053, the USB power is not present, connects the Li-Ion which is a constant current, constant voltage, timer battery to the application load via a low loss Mosfet in terminated single Li-Ion charger. The LTC4053 also order to maximize battery run time. features a die temperature limit to avoid excessive QUICK START PROCEDURE Demonstration circuit 567 is easy to set up to 8. To simulate an over-temperature condition, evaluate the performance of the LTC4410/LTC4053. connect a 2k resistor between the NTC pin and ground. Charging should stop and the Fault LED LTC4053 Charger Function will light up. 1. Place the Charger Enable Jumper in the ON 9. Continue to increase the battery voltage. As the position. battery voltage reaches 4.2V the charge current will rapidly diminish. As the charge current falls under 2. Place the Mode jumper in the 500mA position. 45mA the Charging LED will go out. 3. Connect the input supply, USB load resistor, USB Power Manager Function meters and simulated battery as shown in Figure 1. USB 500mA mode 4. Turn on the power at the input. 10. Connect a 0-500mA load to the terminals NOTE: Make sure that the input voltage does not designated USB device. This simulates the actual exceed 6V. application load. 5. Turn on the simulated battery power supply and set 11. Reduce the battery voltage to about 3.6V so the voltage to 0V. that normal charging is resumed. 6. Note trickle charge current of approximately 45mA. 12. Increase the USB application load current from 7. Increase the voltage of the simulated battery. As 0mA to 500mA and note that as the application the battery voltage reaches 2.7V the charge current load current increases the battery charging should increase to 440mA. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC567 USB BATTERY CHARGER current decreases, so that the input current drawn 19. Increase the USB application load from 0 - from the USB cable remains constant. 100mA and note that as the application current increases the charge current decreases in such USB Suspend Mode a way as to maintain the input current under 13. Move the Charger Enable Jumper to OFF 100mA. 14. Verify that the Mode jumper is in the 500mA Battery Powered Operation position 20. Turn off the input supply and note that the USB 15. Set the current draw of any USB Device load to load is now supplied from the battery. Note also zero the voltage drop from the battery to the load is 16. Note that the input current to the demo board is small due to the use of a Mosfet to switch the less than 200uA, which complies with the USB battery to the load. suspend mode spec. USB Low power Mode 17. Re-enable the charger by placing the Charger Enable jumper in the ON position. 18. Move the Mode jumper to 100mA. 2