DEMO MANUAL DC1721B-A/DC1721B-B LTC4000EGN(-1)/LTC3789EGN 14.6V, 5A Battery Charger with 6V to 36V Buck-Boost Converter IN IN DESCRIPTION Demonstration circuit 1721B is a 14.6V, 5A battery charger wide variety of portable applications including instruments, and PowerPath manager with 6V to 36V buck-boost industrial equipment, power tools, and computers. It has IN IN 2 2 converter featuring the LTC4000/LTC3789, targeted at a total footprint area of 12.4cm (3.6cm for the LTC4000 4-cell LiFePO applications. The output of this demo board circuit only). Synchronous rectification helps to attain 4 was specifically tailored for a Tenergy 10A-hour battery, efficiency exceeding 96% at full load and nominal input. P/N 30207. Other voltages can be set by changing ROFB2 DC1721B-A: The LTC4000 has an input current limit/ and RBFB2. The desired nominal voltage can be accurately regulation loop that prevents overloading sources with trimmed by using trim resistors R42 and R43. For example, limited output capability. for 14.4V battery float voltage, change ROFB2 and RBFB2 DC1721B-B: The LTC4000-1 instead has an input voltage to 86.6k, and add 7.5M at R42 and R43 for greater set regulation loop for Maximum Power Point (MPP) control. point accuracy. MPP control extracts near maximum power from high This circuit was designed to demonstrate the high levels of impedance sources such as solar panels, wind turbines, performance, efficiency, and small solution size attainable or fuel cells. using these ICs in a buck-boost converter battery charger, Design files for this circuit board are available at intelligent PowerPath manager, and power supply. It oper- DEMO MANUAL DC1721B-A/DC1721B-B QUICK START PROCEDURE Demonstration circuit 1721 is easy to set up to evaluate the 7. Turn on the power at the input. performance of the LTC4000/LTC3789. Refer to Figure1 NOTE. If there is no output, temporarily disconnect the for proper measurement equipment setup and follow the load to make sure that the load is not set too high. procedure below: 8. Once the proper VOUT-SYS is again established, adjust WARNING: BATTERIES ARE POTENTIALLY DANGER- the load and/or source within the operating range and OUS HIGH ENERGY SOURCES. IMPROPER CON- observe the output voltage regulation, ripple voltage, NECTION, OVERCHARGE, OR RAPID DISCHARGE efficiency, input and output current limit, and other COULD RESULT IN EXPLOSION AND/OR FIRE. desired parameters. NOTE. When measuring the output voltage ripple, care must 9. Turn off the power at the input. be taken to avoid a long ground lead on the oscilloscope 10. Connect the output load and meters to the BAT output. probe. Measure the output voltage ripple by touching the probe tip and ground ring directly across the last output 11. Set CHARGE jumper to ENABLE. capacitor as shown in Figure 1. 12. Turn on the power at the input. 1. Set MODE jumper to CCM. Set CHARGE jumper to 13. Once the proper VOUT-SYS is again established, adjust DISABLE. the load and/or source within the operating range and 2. Set an input power supply that is capable of 6V to 36V observe the battery float voltage regulation and other and 12A to 24V. Then turn off the supply. desired parameters. 3. With power off, connect the supply to the input terminals 14. Set the load to constant voltage mode to more easily VIN and GND. observe charge current and trickle charge current. NOTE. 15. (DC1721B-B 0NLY) In order to observe MPP operation, add a 0.25 to 0.3, 10W resistor in series with the a. Input voltages lower than 6V can keep the converter DC source and set the source to 13V. Use a constant from turning on due to the undervoltage lockout feature voltage or constant resistance load characteristic. As of the LTC4000. the load is increased, the input voltage will be regulated b. If efficiency measurements are desired, refer to Figure1 at the MPP regulation point (11.75V) by reducing the for test setup. output of the DC/DC converter. 4. Turn on the power at the input. NOTE. Operation in the Instant-On region (V < 12.5V) OUT may engage thermal limit circuit to protect Q7 in the linear NOTE. Make sure that the input voltage never exceeds 36V. region. 5. Check for the proper VOUT-SYS of 15.3V. Turn off the NOTE. The optional thermal limit circuit for Q6 (Q9, RNTC3, power at the input. R55-59, and U4) is included to protect Q6 in case of an 6. Once the proper output voltages are established, con- extended short circuit on VOUT-SYS under adverse thermal nect a variable load capable of sinking 7A at 16V to the conditions (T > 40C). It may not be needed in applica- A output terminals VOUT-SYS and GND. Set the current tions with less severe thermal conditions, lower current for 0A. available to VOUT-SYS, or where continuous short-circuit protection on VOUT-SYS is not required. dc1721bf 2