QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 965A SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER LTC3835EGN-1 DESCRIPTION Demonstration circuit 965A is a single output high an external ramp voltage signal during power-up and frequency step-down DC/DC converter featuring the power-down. Also, the built-in current foldback pre- vents the overheating of output MOSFETs during low quiescent current LTC 3835 in a 16-pin GN short-circuit. package. The DC965A is programmed to generate a regulated 3.3V 5A output from a 4.5V to 36V input All these features make the circuit a high performance voltage. solution for applications in automotive and battery- operated systems, telecom and distributed DC power To maximize battery usage, the demo circuit allows systems. low dropout operation when the input voltage is close to the output voltage. Its selectable burst mode op- Design files for this circuit board are available. Call eration reduces the IC supply current at light loads to the LTC factory. extend battery life. The phase-lockable frequency al- lows the LTC3835 to be synchronized by an external LTC is a registered trademark of Linear Technology Corporation signal. The output voltage of the LTC3835 can track Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION MINIMUM TYPICAL MAXIMUM Input Voltage Range 4.5V 36V Maximum Output Current 4.5V < V < 36V 5A IN Output Voltage V 0A < I < 5A 3.234V 3.3V 3.366V OUT OUT Output Ripple V I = 5A (20MHz BW) V = 36V, F = 400kHz 36mV OUT OUT IN SW PP Nominal Switching Frequency 400kHz Efficiency V = 14V, I = 3.5A, 400kHz Switching Frequency 91.5% IN OUT QUICK START PROCEDURE Demonstration circuit 965A is easy to set up to evalu- MODE jumper (JP3) in desired Mode (Burst, CCM ate the performance of the LTC3835EGN-1. Refer to or DCM) position. Table 2 shows the default setting Figure 1 for proper measurement equipment setup for DC965A. and follow the procedure below: JP1 JP2 PLLPF JP3 MODE JP4 V OUT NOTE: When measuring the input or output voltage TRACK/SS ripple, care must be taken to avoid a long ground lead SS 400kHz DCM ON on the oscilloscope probe. Measure the input or out- put voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See Table 2. Default Jumper Settings Figure 2 for proper scope probe technique. 2. With power off, connect a 4.5V-36V, 6A power 1. Place VOUT jumper in the OFF position, the PLLPF supply to VIN and GND. jumper (JP2) at the selected frequency and the 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 965A SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER 3. Connect a load to VOUT and GND (maximum load NOTE: If there is no output, temporarily disconnect is 5A). the load to make sure that the load is not set too high. 4. Move the VOUT jumper to the ON position. 7. Once proper output voltages are established, adjust 5. Turn on the power at the input. the load within the operating range and observe the NOTE: Make sure that the input voltage is above output voltage regulation, ripple voltage, efficiency 4.5V, but does not exceed 36V. and other parameters. 6. Check for proper output voltages. VOUT should measure 3.3V (could vary from 3.234V to 3.366V). Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2