DEMO MANUAL DC1755A LTC3860EUH Wide Input Range, High Efficiency Step-Down DC/DC Converter DESCRIPTION Demonstration circuit DC1755A provides the user with The main features of the board are listed below: two high current dual phase synchronous buck converters High efficiency and high current density. driven by the LTC3860. These buck converters provide Remote sensing for each output. outputs of 1.5V/50A and 1.2V/50A over an input voltage range of 6V to 14V and a switching frequency of 500kHz. Optional resistors to tie the two outputs together. The board can be easily modified for a 4-phase, single V , O Connector and header to tie two or more boards together 100A supply. The power stage for each phase consists for up to 12-phase operation. of the tri-state PWM compatible 6mm 6mm Fairchild DrMOS module and a 0.47H 13.2mm 12.8mm iron RUN, PGOOD and TRACK/SS pins for each output. powder type inductor from Wrth. A high density, two CLKIN and CLKOUT pins. sided drop-in layout is used. The entire converter, excluding the bulk output and input capacitors, fits within a 2.25 Onboard bias voltage regulator. 1.38 area on the board. BNC connectors to monitor each output voltage. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Design files for this circuit board are available at DEMO MANUAL DC1755A QUICK START PROCEDURE + Note 3. Do not apply the load from the VOSA turret to Demonstration circuit 1755A is easy to set up to evalu- + the VOSA turret or from the VOSB turret to the VOSB ate the performance of the LTC3860EUH. Please refer to turret. These turrets are only intended to monitor the Figure 1 for proper measurement equipment setup and voltage across COUT3 and COUT13 respectively. Heavy follow the procedure below. load currents applied across these turrets may damage 1) With power off, connect the input supply, load and the converter. meters as shown in Figure 1. Preset the load to 0A and V supply to be 0V. Place jumpers in the following IN DYNAMIC LOAD CIRCUIT (OPTIONAL) positions: Demonstration circuit 1755A provides a simple load step JP1 RUNA ON circuit consisting of a MOSFET and sense resistor for each JP2 RUNB ON rail. To apply a load step, follow the steps below. JP3 INT PWR BLK BIAS ON 1) Preset the amplitude of a pulse generator to 0.0V and 2) Adjust the input voltage to be between 6V to 14V. V OUTA the duty cycle to 5% or less. should 1.5V 2%. 2) Connect the scope to the VOUT BNC connectors for V should 1.2V 2%. OUTB the rail under test with a coax cable. To monitor the 3) Next, apply 50A load to each output and remeasure load step current, connect the scope probe across the V . + OUT ISTEP turrets for that rail. 4) Once the DC regulation is confirmed, observe the output 3) Connect the output of the pulse generator to the PULSE voltage ripple, load step response, efficiency and other GEN turret for the rail under test and connect the return parameters. to one of the GND turrets. Note 1. No airflow is required at room temperature with 4) With the converter running, slowly increase the 50A on both outputs. But for ambient temperatures higher amplitude of the pulse generator output to provide the than 30C, a cooling fan is recommended. desired load step pulse height. The scaling for the load step signal is 10mV/A. Note 2. Use the BNC connectors labeled V or V OUTA OUTB to measure the output voltage ripple. dc1755af 2