DEMO MANUAL DC2172A LTC7138 High Efficiency, High V , IN Step-Down Regulator Description Demonstration circuit 2172A is a high input voltage, 400mA FBO turret to tie two or more LTC7138 regulators to- step-down regulator featuring the LTC7138. The output of gether if the application requires more load current. the regulator can be programmed for either 5V, 3.3V or Optional UVLO and OVLO divider. 1.8V with on-board jumpers or is adjustable from 800mV External/internal soft-start. to V using an optional feedback divider. The input voltage IN range is from 4V to 140V. The LTC7138s Burst Mode For more details, refer to the LTC7138 data sheet. The operation, low quiescent current and internal top FET LTC7138 data sheet gives a complete description of the switch provide high efficiency over a wide range of loads. IC operation and application information. The data sheet must be read in conjunction with this quick start guide. Other features include: Design files for this circuit board are available at Optional components to adjust the current limit, make it DEMO MANUAL DC2172A Quick s Dp Demonstration circuit 2172A is easy to set up to evaluate Note 1. CAUTION: The maximum input voltage of the the performance of the LTC7138. Please refer to Figure 1 DC2172A is 140V. Voltages of 140V or lower are high for proper measurement equipment setup and follow the enough to cause electric shock. Use great care when procedure below. testing this demo board. 1) With power off, connect the input supply, load and Note 2. For a 5V output, the input voltage should be 6V meters as shown in Figure 1. Preset the load to 0A and or more. V supply to 0V. IN Note 3. When measuring the output or input voltage ripple, 2) Place the RUN pin jumper (JP3) in the ON position. do not use the long ground lead on the oscilloscope probe. See Figure 2 for the proper scope probe technique. Short, 3) Set the output to 5V by placing the JP1 jumper in the stiff leads need to be soldered to the (+) and () terminals B position and the JP2 jumper in the A position. of an output capacitor. The probes ground ring needs to 4) Turn-on the V supply and increase to 12V. The 5V touch the () lead and the probe tip needs to touch the IN output should be 5V 2% per the Performance Sum- (+) lead. mary table. 5) Next, apply 400mA load to the output and re-measure V . OUT 6) Once the DC regulation is confirmed, observe the output voltage ripple, load step response, efficiency and other parameters for the 5V, 3.3V and 1.8V output settings. dc2172af 2 ure roce tart