DEMO MANUAL DC1898A LTC3899EFE Triple Output Synchronous Step-Up/ Dual Step-Down Supply Description Demonstration circuit 1898A is a triple output syn- The LTC3899EFE buck outputs are supplied from the boost chronous step-up/dual step-down supply featuring the output. With this boost-then-buck topology, the buck LTC3899EFE. The circuit is using a drop-in layout: the outputs maintain regulation over the entire input range. main buck circuit components fit in an area of 1, The resultant wide input voltage range of 2.5V to 60V is while the main boost circuit area is 1. The pack- suitable for automotive or other battery fed applications age style for the LTC3899EFE is a 38-pin exposed pad where low quiescent current is important. The LT3899EFE TSSOP package. data sheet gives a complete description of the part, opera- tion and application information. The data sheet must be The main features of the board include rail tracking (buck read in conjunction with this quick start guide for demo channels only), an internal 5V linear regulator for bias, circuit 1898A. separate RUN pins for each output, a DRVSET jumper to set the gate drive voltage and a Mode selector that allows Design files for this circuit board are available at the converter to run in CCM, pulse skip or Burst Mode DEMO MANUAL DC1898A Quick s p D Demonstration circuit DC1898A is easy to set up to 2. With power off, connect the input power supply to V IN evaluate the performance of the LTC3899EFE. Refer to and GND. Figure 1 for proper measurement equipment setup and 3. Turn on the power at the input. follow the procedure below: NOTE. Make sure that the input voltage does not exceed 60V. NOTE. When measuring the input or output voltage ripple, 4. Check for the proper output voltages. care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage V = 4.900V to 5.100V, OUT1 ripple by touching the probe tip directly across the V IN V = 8.330V to 8.670V OUT2 or V and GND terminals or directly across relevant OUT capacitor. See Figure 2 for proper scope probe technique. V = 9.700V to 10.300V OUT2 1. Place jumpers in the following positions: NOTE. If there is no output, temporarily disconnect the load to make sure that the load is not set too high. JP1: ON 5. Once the proper output voltages are established, adjust JP2: ON the loads within the operating range and observe the JP4: ON output voltage regulation, ripple voltage, efficiency and JP5: Burst Mode other parameters. JP8: 6V I OUT1 + + V OUT1 LOAD V OUT2 LOAD I OUT2 + + I OUT3 I IN V OUT3 + + LOAD + + V IN VIN SUPPLY dc1898 F01 Figure 1. Proper Measurement Equipment Setup dc1898af 2 ure roce tart