DEMO MANUAL DC1822A LTC3861EUHE High Current, Dual Output Synchronous Buck Converter Description Demonstration circuit 1822A is a dual output synchronous The main features of the board are: buck converter featuring the LTC 3861EUHE. The board Remote sensing for each output, where the divider provides two outputs of 1.5V/25A and 1.2V/25A from is placed before a high input impedance differential an input voltage of 7V to 14V at a switching frequency amplifier. of 500kHz. The power stage consists of a 6mm 6mm CLKIN and CLKOUT pins. DrMOS and a 13mm 13mm iron powder type inductor. An on-board 5V LT 3470 buck regulator provides the 5V Optional resistors to tie the two outputs together. bias for the LTC3861 and the DrMOS. Connector and header to tie two or more boards together The demo board uses a high density, two sided drop-in for up to 12-phase operation. layout. The power components, excluding the bulk output Optional footprint for an LTC4449 gate driver and and input capacitors, fit within a 1.5 1.2 area on the discrete MOSFETs. top layer. The control circuit fits in a 1.1 1.0 area on the bottom layer. The package style for the LTC3861EUHE Optional footprint for a dual phase Delta power block. is a 36-lead 5mm 6mm QFN. Design files for this circuit board are available at L, LT, LTC, LTM, Module, Linear Technology and the Linear logo are registered trademarks of DEMO MANUAL DC1822A Quick s tart p D Demonstration circuit 1822A is easy to set up to evaluate 3. Next, apply 25A load to each output and re-measure the performance of the LTC3861EUHE. Please refer to VOUT. Figure 1 for proper measurement equipment setup and 4. Once the DC regulation is confirmed, observe the output follow the procedure below. voltage ripple, load step response, efficiency and other 1. With power off, connect the input supply, load and parameters. meters, as shown in Figure 1. Preset the load to 0A NOTE 1. Use the BNC connectors labeled VOUT1 or and V supply to be 0V. Place jumpers in the following IN VOUT2 to measure the output voltage ripple. positions: NOTE 2. Do not apply the load from the VOS1+ turret to JP1 RUN1 ON the VOS1 turret or from the VOS2+ turret to the VOS2 JP2 RUN2 ON turret. These are connected to the sense traces for the output voltage. Heavy load currents applied across these JP3 INT BIAS ON turrets may damage these traces. 2. Adjust the input voltage to be between 7V to 14V. VOUT1 should be 1.5V 2%.VOUT2 should be 1.2V 2%. + + V V OUT1 OUT2 LOAD LOAD A A I I OUT1 OUT2 Monitor voltage across C OUT5 and C for accurate OUT10 efciency measurements. + + V V V V OUT1 OUT2 * * + V V IN dc1822a F01 A I IN + V SUPPLY IN Figure 1. Proper Measurement Equipment Setup dc1822af 2 ure roce