DC1626A-A Analog Devices

DEMO MANUAL DC1626A LTC3838EFE Wide Input Range, High Efficiency Step-Down DC/DC Converter DESCRIPTION Demonstration circuit 1626A is a dual output 1.5V/15A The main features of the board are listed below: and 1.2V/15A synchronous buck converter operating with MODE jumper to program either DCM or FCM at light a switching frequency of 300kHz over an input voltage or no load range of 4.5V to 26V. The demo board comes in two ver- EXTVCC pin sions. The -A version uses inductor DCR current sensing with an iron powder inductor for high efficiency. The -B PLLIN pin to synchronize the converter to an external version uses a 2.5m sense resistor for accurate current clock sensing with a low DCR ferrite inductor. The fixed on-time Remote sensing for V OUT1 valley current mode architecture of the LTC3838 allows for a fast load step response (see Figures 6 to 9). The load Optional resistors to tie the two phases together step response can be tested with the on-board load step Each rail has its own RUN pin, PGOOD pin and circuit and a bench pulse generator. TRACK/SS pin The demo board uses a high density, two sided drop-in Design files for this circuit board are available at layout. The entire converter, excluding the bulk output and DEMO MANUAL DC1626A QUICK START PROCEDURE Demonstration circuit 1626A is easy to set up to evalu- Load Step Transient Testing ate the performance of the LTC3838EFE. Please refer to Demonstration circuit 1626A provides a simple load step Figure1 for proper measurement equipment setup and circuit consisting of a MOSFET and sense resistor for each follow the procedure below. rail. To apply a load step, follow the steps below. 1. With power off, connect the input supply, load and 1. Preset the amplitude of a pulse generator to 0.0V and meters as shown in Figure 1. Preset the load to 0A the duty cycle to 5% or less. and V supply to be 0V. Place jumpers in the following IN 2. Connect the scope to the V BNC connectors for positions: OUT the rail under test with a coax cable. To monitor the JP4 RUN1 ON load step current, connect the scope probe across the JP1 RUN2 ON IOSTEP+/IOSTEP turrets for that rail. JP3 MODE FCM 3. Connect the output of the pulse generator to the PULSE GEN turret for the rail under test and connect the return 2. Adjust the input voltage to be between 4.5V to 26V. to one of the GND turrets. V should 1.2V 2%. OUT1 4. With the converter running, slowly increase the ampli- V should 1.5V 2%. OUT2 tude of the pulse generator output to provide the desired 3. Next, apply 15A load and recheck V . OUT load step pulse height. The scaling for the LOAD STEP signal is 10mV/A. 4. Once the DC regulation is confirmed, observe the output voltage ripple, load step response, efficiency and other parameters. Note 1. Use the BNC connectors labeled V or V OUT1 OUT2 to measure the output voltage ripple. Note 2. Do not apply the load from the VO1 SNS+ turret to the VO1 SNS turret or from the VO2+ turret to the VO2 turret. These turrets are only intended to monitor the voltage across COUT1 and COUT5 respectively. Heavy load currents applied across these turrets may damage the converter. dc1626afa 2