DC1094 LTC4095 QUICK START GUIDE LTC4095 Standalone USB Li-Ion/Polymer Battery Charger in 2mm x 2mm DFN DESCRIPTION Demonstration circuit 1094 is a Standalone USB Li- resistor to make a complete battery charger circuit, mak- Ion/Polymer Battery Charger in 2mm x 2mm DFN featur- ing it an ideal solution for portable USB power applica- ing the LTC4095. tions. The LTC4095 may provide up to 950mA of charge cur- Refer to the LTC4095 datasheet for more information on rent programmed by a single resistor. The HPWR pin this part. allows the current to be set at 100% or 20% full charge Design files for this circuit board are available. Call current. The LTC4095 also has an NTC thermistor input the LTC factory. to monitor battery temperature, C/10 current detection L, LTC, LTM, LT, are registered trademarks of Linear Technology Corporation. Other prod- output, bad battery detection, and low battery trickle uct names may be trademarks of the companies that manufacture the products. charge. The final float voltage is preset to 4.2V. The LTC4095 only requires an input capacitor and a program PERFORMANCE SUMMARY Specifications are at T = 25C A PARAMETER CONDITION VALUE USB IN Voltage Range IN 4.3V 5.5V Output Float Voltage V Constant Voltage Mode 4.200V ( 0.5%) BAT Charge Current I HPWR Jumper = 100%, R = 1.74K 460mA BAT PROG Charge Current I HPWR Jumper = 20%, R = 1.74K 92mA BAT PROG Charge Current I USB Input Power Trickle Charge Mode, R = 1.74K 46mA BAT PROG V Full Charge Current, HPWR Jumper = 100% 1V PROG 1/5 Full Charge Current V 200mV PROG HPWR Jumper= 20% V Trickle Charge Current 100mV PROG OPERATING PRINCIPLES Demonstration Circuit 1094 is programmed to provide current, battery charge current, NTC thermistor current, 460mA full charge current with the HPWR jumper, JP1, and IC quiescent current. Moving the HPWR jumper in the 100% position. The input current to this demon- from the 100% position to the 20% position limits the stration circuit may be 470mA total with the CHRG LED charge current to 92mA. 1 LTC4095 QUICK START PROCEDURE Demonstration circuit 1094 is easy to set up to evaluate 6. Increase the Battery Simulator supply to 3V and the performance of the LTC4095. The charger may be observe that the LTC4095 charge current will jump evaluated using an actual Li-Ion battery, a bi-polar to a full charge current of 460mA. supply, or a battery simulator. A battery simulator 7. Slowly decrease the USB IN voltage until the CHRG consists of an adjustable supply with a load resistor LED suddenly shuts off. The USB IN voltage is ap- across the supply output. A 3.6 5W resistor value proximately at the falling Under Voltage Lockout will provide an 800mA load at 2.9V. This will allow the threshold. power supply to sink and source current similar to a 8. Set the USB IN voltage to 5V and slowly increase battery, but allows the battery voltage to be changed the Battery Simulator voltage until the charge cur- quickly or remain at the same value indefinitely. rent or the PROG voltage starts to decrease. The Refer to Figure 1 for proper measurement equipment charger is now in constant voltage mode. setup and follow the procedure below: NOTE. When measuring the input or output voltage ripple, care must be 9. Slowly increase the Battery Simulator voltage until the taken to avoid a long ground lead on the oscilloscope probe. Measure the CHRG LED shuts off. This is approximately when the input or output voltage ripple by touching the probe tip directly across the charge current has decreased to 10% of its full value. USB IN or BAT and GND terminals. See Figure 2 for proper scope probe technique. 10. Continue to slowly increase the Battery Simulator voltage while observing the charge current. When 1. Place jumpers in the following positions: the charge current decreases to 0mA the device is JP1. HPWR = 100% (Up) in Standby Mode. JP2. SUSP = HI (Up) 11. Slowly decrease the Battery Simulator voltage un- JP3. NTC = INT (Down) til the CHRG LED illuminates. This is the recharge voltage threshold. 2. With the power supplies adjusted to 0V, connect the USB IN power supply and Battery or Battery 12. Move the HPWR jumper, JP1, from the 100% to Simulator with series ammeters, as illustrated in the 20% position. Observe that the charge current Figure 1. An ammeter or a 100m current sense is 20% of its full value, about 92mA. resistor may be used to measure the battery charge 13. Move the NTC jumper, JP3, from INT to EXT and current. observe the CHRG LED blinking at 1.5Hz with a 3. Connect voltmeters, as shown in Figure 1, across 50% duty cycle. With an oscilloscope on the CHRG the USB IN and GND terminals, and across the BAT terminal, observe a 35KHz signal pulsing at 6.25% and GND terminals. These voltmeters may also be and 93.75% duty cycles. used to measure the voltage on the PROG terminal. 14. With a clip-to-clip test lead, connect the NTC termi- 4. Turn on the Battery Simulator supply to 2.5V and nal to the GND terminal. Observe the CHRG LED is on set the SUSP jumper to the LO position. steady and the charge current is about 92mA. The NTC function is now disabled. NOTE. Make sure that the battery voltage does not exceed 6V. 15. With the NTC and HPWR jumpers in their present 5. Increase the USB IN voltage until the CHRG LED positions, (EXT & 20% respectively), move the SUSP illuminates and observe the USB IN voltage and jumper, JP2, to the HI position, and remove the test charge current. The USB IN voltage is approxi- lead from the NTC and GND terminals. Observe that mately at the rising Under Voltage Lockout thresh- the input current is 17uA or less. The LTC4095 is now old. The LTC4095 will be in trickle charge mode in Suspend Mode. with a trickle charge current of 46mA. NOTE. Make sure that the input voltage does not exceed 7V. 2