DEMO MANUAL DC2253A LTC3789EGN 300W 2-Phase Interleaved Synchronous Buck-Boost Converter Description Demonstration circuit 2253A is a high power, high ef- The light load operating mode of the controller is de- ficiency, 2-phase interleaved synchronous buck-boost termined through the MODE/PLLIN pin. By default, the converter with a 6V to 36V input range. It can supply a forced continuous mode (CCM) operation is pre-selected 25A maximum load current with a 12V output. This demo on this demo board. Switching frequency is preset at board features 2x LTC3789EGN controllers. about 200kHz. Two paralleling schemes are available for this demo board and by default the method of shared I TH The LTC 3789 is a high performance current-mode pins is adopted. Please refer to the Quick Start Procedure buck-boost switching regulator controller that operates section for the optional Master-Slave paralleling scheme. from input voltages above, below or equal to the output To shut down the converter, force the RUN pin below 1.2V voltage, while an output current feedback loop provides (JP1: OFF) Please refer to LTC3789 data sheet for more support for output current limit and battery charging. With detailed information. a wide 4V to 38V (40V maximum) input and output range and seamless, low noise transitions between operating Design files for this circuit board are available at regions, the LTC3789 is ideal for automotive, telecom and DEMO MANUAL DC2253A Quick s p D Demonstration circuit 2253A is easy to set up to evaluate Optional Master-Slave Paralleling Scheme the performance of the LTC3789EGN. Refer to Figure 1 Besides the default paralleling scheme by tying the I pins TH for the proper measurement equipment setup and follow together, another optional Master-Slave scheme can be the procedure below: achieved on the demo board to obtain a better sharing of 1. With power off, connect the input power supply to V the inductor currents and output currents between phases. IN (6V to 36V) and GND (input return). Please refer to the schematic in Page 8. To implement it, 2. Connect the 12V output load between V and GND 1. Remove R67, R69 and R70. OUT (Initial load: no load). 2. Populate R68, R71 with 0. 3. Connect the DVMs to the input and output. Set the 3. Set R 5~10% higher than R and set R = R . FB3 FB1 FB4 FB2 default jumper position, JP1: ON. 4. Choose the current reference divider R65 and R66 so 4. Turn on the input power supply and check for the proper that when the Vout is regulated, the voltage drop on output voltages. V should be 12V 2%. OUT R65 is equal to V , where V is the output current ILIM ILIM 5. Once the proper output voltages are established, ad- limit threshold voltage. For example, when I pin is LIM just the loads within the operating range and observe grounded, V = 50mV. For V = 12V, select R65 ILIM OUT the output voltage regulation, ripple voltage and other = 100 and R66 = 24k and then the voltage drop on parameters. R65 will be 50mV. Note: When measuring the output or input voltage ripple, do not use the long ground lead on the oscilloscope probe. See Figure 2 for the proper scope probe technique. Short, stiff leads need to be soldered to the (+) and () terminals of an output capacitor. The probes ground ring needs to touch the () lead and the probe tip needs to touch the (+) lead. dc2253af 2 ure roce tart