DEMO MANUAL DC2129A LTC3119UFD 18V, 5A Synchronous Buck-Boost DC/DC Converter Description Demonstration circuit 2129A features the LTC 3119, an of the converter is shown in Figure 2 and Figure 3. The 18V, 5A synchronous buck/boost DC/DC converter. The converter is built on a four layer board using 2oz copper DC2129A has been designed for an input voltage range on each layer for better thermal performance. The spac- of 2.5V to 18V with an output voltage (V ) set to 5V. ing between the layers has been reduced so the overall OUT For V > 5V the output current can be as high as 5A. The board thickness is 0.031 inches allowing for better heat IN unique 4-switch, single inductor architecture provides low transfer between layers and aiding in heat distribution noise and seamless operation from input voltages above, across the board. The thermal performance of the demo below, or equal to the output voltage. board is shown in Figure 4. The converter can also oper- ate in a maximum power point control mode by setting The LTC3119 features selectable PWM or Burst Mode the JP2 jumper to the ON position. The MPPC point can operation, and an easily synchronizable oscillator. A be adjusted by changing R10 and R11. Consult the data jumper JP3, is provided to select the operating mode. A sheet for more information. clock signal can also be applied to JP3 if synchronization is desired. The demo board is configured for a switching The LTC3119 data sheet has detailed information about the frequency of 750kHz. Jumper JP1 is provided to enable operation, specifications, and applications of the device. the converter. Resistors R8 and R9 can be used to set an The data sheet should be read in conjunction with this accurate turn-on voltage of the converter. quick start guide. Typical demo board efficiency is shown in Figure 1 for Design files for this circuit board are available at several input voltages as a function of load current. Consult DEMO MANUAL DC2129A Quick s tart p D Using short twisted pair leads for any power connections 4. Move jumper JP1 to ON. Turn on the power supply and and with all loads and power supplies off, refer to Figure slowly increase voltage until the voltage at V is 2.5V. IN 5 for the proper measurement and equipment setup. The 5. Verify V is ~5V. OUT power supply should not be connected to the circuit until 6. V can now be varied between 2.5V and 18V. V told to do so in the procedure below. IN OUT should remain in regulation. When measuring the input or output voltage ripple, care 7. I can also be varied from 0A to 5A. For V < 5V, must be taken to avoid a long ground lead on the oscil- OUT IN maximum I is reduced. This reduction is due to I loscope probe. OUT IN increasing as V decreases. Once the input current IN 1. JP1, JP2, JP3, and load settings to start: limit is reached, V will drop out of regulation. OUT JP1 (RUN) = OFF NOTE: If V drops out of regulation, check to be sure OUT JP2 (MPPC) = OFF the maximum load has not been exceeded, or that V IN JP3 (PWM) = FIXED FREQUENCY is not below the minimum value (2.5V). LOAD = NO LOAD 8. For operation in Burst M ode move jumper JP3 to BURST MODE. I is limited in Burst Mode operation. See the 2. With power OFF connect the power supply as shown in OUT data sheet for more information. Figure 5. If accurate current measurements are desired (for efficiency calculations for example) then connect an ammeter in series with the supply as shown. The ammeter is not required however. 3. Connect the load to V as shown in Figure 5. Again, OUT connect an ammeter if accurate current measurement or monitoring is desired. 100 2.4V PWM MODE IN 90 3V PWM MODE IN 5V PWM MODE IN 80 10V PWM MODE IN 18V PWM MODE IN 70 2.5V Burst Mode OPERATION IN 3V Burst Mode OPERATION IN 60 5V Burst Mode OPERATION IN 10V Burst Mode OPERATION IN 50 18V Burst Mode OPERATION IN 40 30 20 10 0 0.00001 0.0001 0.001 0.01 0.1 1 10 LOAD CURRENT dc2129a F01 Figure 1. Typical Efficiency as a Function of Input Voltage and Load Current dc2129af 2 EFFICIENCY (%) ure roce