QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1267A STEP-UP DC/DC REGULATOR LTC3125EDCB DESCRIPTION Demonstration circuit 1267A is a step-up DC/DC rent limit can be adjusted by replacing one resis- regulator featuring the LTC3125EDCB and is ide- tor. ally suited for pulsed load applications where the The LTC3125 datasheet gives a complete descrip- input current needs to be limited. Demonstration tion of the part, operation and application informa- circuit 1267A is configured for 500mA maximum tion and must be read in conjunction with this input current limit and can handle pulsed load cur- quick start guide for demo circuit 1267A. rents of up to 2A, with duty cycles of up to 15%. Design files for this circuit board are available. The input voltage range is 3.3V 10%. Call the LTC factory. The package style for the LTC3125EDCB is an 8 Burst Mode is a trademark of Linear Technology Corporation lead 3mm x 2mm plastic DFN. The fixed input cur- Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Input Voltage Range 3.0V 3.6V Input Current Limit 500mA 5% Output Voltage V V = 3.0V to 3.6V, I = 0A to 500mA 4.0V 4% OUT IN IN V = 3.0V, I = 500mA 300mA IN IN Output Current I OUT V = 3.6V, I = 500mA 400mA IN IN V = 3.0V, I = 300mA 89.8% typical IN OUT Efficiency (Figure 4) V = 3.6V, I = 400mA 91.4% typical IN OUT QUICK START PROCEDURE Demonstration circuit 1267A is easy to set up to 2. With power off, connect the input power supply evaluate the performance of the LTC3125EDCB. to Vin and GND. Refer to Figure 1 for proper measurement equip- 3. Turn on the power at the input. ment setup and follow the procedure below: NOTE: Make sure that the input voltage does not NOTE: When measuring the input or output voltage exceed 4V. ripple, care must be taken to avoid a long ground 4. Check for the proper output voltage. lead on the oscilloscope probe. Measure the input Vout = 3.84V to 4.16V, or output voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals If there is no output, temporarily disconnect the or directly across the capacitor. See Figure 2 for load to make sure that the load is not set too proper scope probe technique. high. 1. Place the jumper in the following position: 5. Once the proper output voltage is established, JP1 On adjust the load within the operating range and 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1267A STEP-UP DC/DC REGULATOR observe the output voltage regulation, ripple 6. The method for evaluating pulsed loads will be voltage, efficiency and other parameters. discussed in the next section. Vout Load - + Vout Optional Circuit for Pulsed Loads + - A Iout V - Pulse Generator + 0-5V BNC cable to scope 10mV/A - + V A Iin Vin + - Vin supply Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple Directly Across Bulk Capacitor 2