DC882A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 882 SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING LTC3809EDD-1 DESCRIPTION Demonstration circuit 882 is a small size, low profile, rent sense threshold can be easily selected with IPRG low cost and high efficiency synchronous step-down pin. Switching frequency is internally set at 550KHz. DC/DC converter featuring the LTC3809EDD-1 controller. The demo board has optional power component foot- The demo board is capable of providing 2A output cur- prints to deliver higher output current and a tracking rent with 2.75V to 9.8V input range. Burst mode/Pulse function, allowing Vout to track an external voltage sig- skipping/Forced continuous operation is selectable. The nal at the TRACK terminal (JP4: Track). constant frequency current mode architecture with Design files for this circuit board are available. Call MOSFET V sensing eliminates the need for a sense re- DS the LTC factory. sistor and improves efficiency. The maximum peak cur- LTC is a trademark of Linear Technology Corporation Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Input Voltage Range 2.75V to 9.8V V V = 2.75V-9.8V, I = 0A to 2A 1.8V 2.5% OUT IN OUT Maximum load current I V = 2.75V-9.8V 2A OUT IN Typical Output Ripple Voltage V = 3.3V, I = 2A (20MHz BW) 8mV IN OUT PP Typical Switching Frequency 550kHz QUICK START PROCEDURE Demonstration circuit 882 is easy to set up to evaluate 2. Connect the 1.8V load between Vout and GND (Initial the performance of the LTC3809-1. Refer to Figure 1 for load: 0 A). proper measurement equipment setup and follow the 3. Connect the DVMs to the input and output. procedure below: (Initial jumper positions: JP1 se- 4. Turn on the input power supply and check for the lected JP4: Soft Start) proper output voltage. Vout should be 1.8V+/-2.5%. NOTE: When measuring the input or output voltage rip- 5. Once the proper output voltage is established, adjust ple, care must be taken to avoid a long ground lead on the load within the operating range and observe the the oscilloscope probe. Measure the input or output output voltage regulation, ripple voltage and other pa- voltage ripple by touching the probe tip directly across rameters. the Vin or Vout and GND terminals. See Figure 2 for proper scope probe technique. 1. With power off, connect the input power supply to Vin (2.75V-9.8V) and GND (input return). 1 GND VIN QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 882 SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2