DC1707A Analog Devices

DEMO MANUAL DC1707 LTC3617EUDD 6A Monolithic Step-Down Regulator for DDR Termination DESCRIPTION Demonstration circuit 1707 is a high efficiency mono- low quiescent current shutdown and for selecting internal lithic step-down DC/DC switching regulator designed for or external compensation. Internal soft-start is included double-data-rate (DDR) memory termination in computer and a PGOOD output terminal that pulls low at start-up systems. The VTT output is capable of sourcing and sink- and when the VTT output is outside a voltage window. The ing up to 6A with an output voltage equal to one-half the LTC3617 is available in the 24-pin 3mm 5mm thermally voltage applied to the V terminal or one-half the input enhanced QFN package. DDQIN supply voltage, selected by a jumper. An additional low The LTC3617 datasheet gives a complete description of the current output (VTTR) also equal to one-half the voltage on part, operation and application information and should be V and can source and sink up to 10mA is included. DDQIN read in conjunction with this quick start guide. Input voltage range is from 2.25V to 5.5V with overvolt- Design files for this circuit board are available at age protection for transients exceeding 6.5V. Switching DEMO MANUAL DC1707 QUICK START PROCEDURE Demonstration circuit 1707 allows the user to quickly 6. To evaluate sourcing current from the VTT terminal, evaluate the performance of the LTC3617. Refer to Figure 1 connect one lead of a 0.2 5W load resistor to the for proper measurement equipment setup and follow the VTT terminal and the other lead to the GND terminal. procedure below Verify that the voltmeter measurements still meet the specifications shown in the table on page 1. 1. Place jumpers in the following positions. JP2 - EXT REF (lower) 7. To evaluate sinking current into the VTT terminal, connect JP1 - RUN (lower) one lead of a 0.5 10 or 20W load resistor to the VTT JP3 - V (upper) terminal and the other lead to the V terminal. Verify IN IN that the voltmeter measurements meet the specifications 2. With both power supplies turned down and switched in the Performance Summary table on the front page. off, connect the supplies and digital voltmeters and ammeters as shown in Figure 1. NOTE. When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the 3. Switch on the input supply and adjust for approximately oscilloscope probe. Measure the input or output voltage 3.3V on V , and set the Reference supply to 1.800V IN ripple by touching the probe tip directly across the V or IN on V . DDQIN V and GND terminals. See Figure 2 for proper scope OUT 4. Verify that the VTTR voltmeter is exactly one-half of probe technique. V 18mV or approximately 900mV. DDQIN NOTE. Additional pads for are located on the board back- 5. Verify that the VTT voltmeter reading is equal to the side for larger compensation components for optimizing VTTR value 10mV. loop compensation. dc1707f 2