QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 569 LI-ION BATTERY CHARGER IN SOT-23 LTC4054-4.2 DESCRIPTION Demonstration circuit 569 is a single cell Li-ion linear charger in a SOT-23. Charge rates as high as 600mA can be achieved due to the LTC4054’s internal die temperature control loop that prevents excessive PCB heating under worst-case conditions. The user is provided with a control jumper to select between OFF/450mA/600mA charge rates. The reduced charge rate is suitable for USB applications. A charge LED illuminates while the charger is charging the battery. Design files for this circuit board are available. Call the LTC factory. Table 1. Performance Summary PARAMETER CONDITION VALUE Input Voltage 4.25–10V IOUT 450mA selected VBAT = 3.6V 450mA ±7% IOUT 600mA selected VBAT = 3.6V 600mA ±7% Float voltage VIN = 5V 4.20v ±1% Trickle Charge threshold VIN = 5V 2.9V ±0.1V C/10 detection VIN =5V VBAT = 4.2 C/9–C/11 Recharge threshold Vin 5V 4.05V+-50mV OPERATING PRINCIPLES Demonstration circuit 569 is a simple single cell Li-ion charger. The demo features the LTC4054-4.2 charger IC. This charger implements a constant die temperature, constant current, and constant voltage charge scheme. Charge termination occurs when the charge rate falls to beneath 10% of the programmed charge current. A topping charge will be applied if the cell voltage falls to 4.05V to insure long-term charge maintenance. Deeply discharged cells are conditioned with a low C/10 trickle current until the cell voltage reaches 2.9V whereupon full charge current is applied. In the event that full charge current would result in excessive dissipation a die temperature control loop backs off the charge current to maintain a reasonable PC board temperature. A charge LED is provided that illuminates every time the charger is charging the battery. The peak charge current is jumper selectable at either 600mA or 450mA. The 450mA rate is intended for USB applications. QUICK START PROCEDURE Demonstration circuit 569 is easy to set up to evaluate the performance of the LTC4054-4.2. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1. Use the jumper provided to select the desired charge rate 450mA or 600mA. 2. With the power off, connect the input power supply to Vin and GND. 3. Connect the demo board to the battery simulator as shown in Figure 1. 4. Set the battery simulator voltage to zero, and then slowly raise the input voltage. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 569 LI-ION BATTERY CHARGER IN SOT-23 When the supply voltage exceeds 4.25V the charger should activate and the charge LED will illuminate. constant die temperature loop is no longer active and the charge current is the programmed charge current. 5. Note that so long as the battery voltage is under the 9. Continue to increase the battery voltage, as the bat- Trickle Charge threshold of 2.9V the charge current is 10% of the selected charge current. tery voltage approaches the float voltage of 4.2V the charge current begins to drop. Note that as the charge current drops to 10% of the programmed current the charger terminates. Charge current falls to zero and the charge LED extinguishes. 6. Increase the battery voltage to about 3V and note that the charge current has increased beyond the trickle charge current. 7. Heat up the LTC4054 by touching a soldering iron to the PCB. Verify that the LTC4054-4.2 thermal loop is working— the charge current should decrease. Remove the iron and the charge current increases. This demonstrates the “constant die temperature” operating mode. 8. Continue to increase the battery voltage. Note that as 10. Slowly decrease the battery voltage to simulate a long term self-discharge of the battery. Note that as the battery voltage drops to 4.05V that another charge cycle is initiated. 11. Place the charge rate selector in the OFF position. Note that the battery current draw is extremely low (approx 1µA) also note that the supply current draw is low (approx 20µA). the voltage drop across the LTC4054 decreases the MEASURE CHARGE CURRENT (IBAT) + – + + + – – VBAT – INPUT POWER SUPPLY 4.25V–10V 1A RECOMMENDED LI-ION BATTERY SIMULATOR* + 2Ω 10W PRELOAD – BATTERY SIMULATOR BENCH POWER SUPPLY 0V–4.5V 3A WITH COURSE AND FINE VOLTAGE ADJUSTMENT * CAN USE A LI-ION BATTERY, THOUGH TESTING TAKES MORE TIME Figure 1. Proper Measurement Equipment Setup 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 569 LI-ION BATTERY CHARGER IN SOT-23 USB APPLICATIONS USB battery chargers based on the LTC4054-4.2 can be created in a variety of ways. One way is to place the USB load parallel to the battery. The advantage to this scheme is that no special measures must be taken with the load in order to gain USB compliance. The disadvantage to this scheme is that all USB power flows through the LTC4054 so some of the USB power is inevitably dissipated in the LTC4054. Additional load current registers as battery current and could potentially disrupt the C/10 termination scheme. The preferred technique for USB charger applications is to use the LTC4410 USB power manager IC available on demonstration circuit 567. The problem is that DC567 combines the LTC4410 and the LTC4053 in a complete USB compliant charging solution. Nevertheless, it is not difficult to disconnect the LTC4053 on DC567 and instead hook up the LTC4054 from DC569. TESTING THE USB-COMPLIANT CHARGER 1. Hook up an adjustable load (0mA–500mA) to the USB Device terminal of the DC567. 2. Hook up the USB input supply 5V, 500mA to the Vin terminal of either demo board. 3. Hook up the simulated battery as previously de- scribed or an actual battery to the battery terminal of DC569. 4. Place the charge current jumper of DC569 in the 450mA USB Appl. position. 5. Simulate the USB low power mode by placing the Mode jumper on DC567 in the 100mA position. 6. Turn on the input supply. 7. Set the simulated battery to some nominal voltage typically 3.6V. 8. Set the load of the USB device to 0mA. COMBINING DC567 AND DC569 TO CREATE A USBCOMPLIANT CHARGER 1. On DC567 separate the LTC4053 from the LTC4410 by using an Xacto knife to cut through the four traces connecting the two halves of the demo board. 2. Connect DC567 and DC569 together as follows. a. GND of DC567 to GND of DC569 b. Vin of DC567 to Vin of DC569 c. CHP/Monitor pin of DC567 to Prog/Monitor pin of DC569 d. From Battery terminal of DC567 to the Battery terminal of DC569 9. Note the charge current to the battery and the input current. 10. Now increase the USB load current, note that the bat- tery current decreases and the input current remains constant and below 100mA 11. Simulate the USB high power mode by placing the mode jumper on DC567 in the 500mA position and repeating steps 8–10. The input current remains below 500mA 12. Simulate the USB suspend mode by setting the mode jumper on DC567 in the 500mA position and by removing the Charge Current jumper from DC569. Note the input current is below 100µA. This creates a USB compliant battery charger. 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 569 LI-ION BATTERY CHARGER IN SOT-23 – – + + – INPUT POWER SUPPLY 5V, 500mA + MEASURE CHARGE CURRENT (IBAT) + – + VBAT RECOMMENDED LI-ION BATTERY SIMULATOR* + 2Ω 10W PRELOAD – – BATTERY SIMULATOR BENCH POWER SUPPLY 0V–4.5V 3A WITH COURSE AND FINE VOLTAGE ADJUSTMENT * CAN USE A LI-ION BATTERY, THOUGH TESTING TAKES MORE TIME CUT ALL TRACES ALONG THIS LINE TO SEPARATE USB POWER MANAGER FROM BATTERY CHARGER – – + + – + LOAD SIMULATED USB DEVICE 0mA–500mA LOAD Figure 2. Combining DC567 and DC569 to Create a USB-Compliant Charger 4 5 4 3 2 1 D D C C 1 CHRG 2 GND 3 BAT PROG 5 VCC 4 B B A A 5 4 3 2 1