DEMO MANUAL DC2006A-A LTC3862-2 High Power, High Voltage Step-Up Converter Description Demonstration circuit 2006A-A is a multiphase high The LTC3862-2 is a multiphase step-up (boost) DC/DC power, high voltage step-up DC/DC converter featuring controller that delivers high output power in a compact the LTC 3862-2 boost controller. This demo board con- footprint. Up to 12 power stages can be paralleled and verts a 6V to 36V input voltage to a 50V output at up to clocked out-of-phase to minimize input and output filtering 10A with four phases by utilizing and synchronizing two requirements. It has a 5.5V to 36V input voltage range and LTC3862-2 controller ICs. an output voltage range that is dependent on the choice of external components. The DC2006A-A supports three ways of biasing the LTC3862-2 controllers ICs by directly from the input The LTC3862-2 utilizes peak current mode architecture for voltage, or from a low power switching power supply or easy loop compensation and multiphase operation with from an LDO regulator. very accurate phase-to-phase current matching. The fixed operating frequency can be set with a single resistor over An onboard SEPIC power supply can provides a stable a 75kHz to 500kHz range or can be synchronized to an 10V bias voltage for both LTC3862-2 controllers over the external clock over a 50kHz to 600kHz frequency range. wide varying input voltage. This allows the use of either A current sense resistor is used in each phase to provide logic level or standard level MOSFETs, even when the input a precise cycle-by-cycle current limit. The powerful on- voltage drops far below the 10V set-point, which is useful board gate drivers minimize switching losses and allow in wide varying input applications. the use of multiple MOSFETs in parallel for very high An onboard LDO regulator can be selected for biasing current applications. the LTC3862-2 controllers, which simplifies the electrical Design files for this circuit board are available at schematic and can be very useful in applications where DEMO MANUAL DC2006A-A Quick s p D Demonstration circuit 2006 is easy to set up to evaluate LTC3862-2 BIAS CIRCUITS the performance of the LTC3862-2 controllers. Refer to The demo board DC2006A supports three ways of biasing Figure 1 for proper measurement equipment setup and LTC3862 controllers. Place jumper BIAS (JP12) to the V IN follow the procedure below: position for input voltage above 10V, but below 36V. In NOTE. When measuring the input or output voltage ripple, this case bias pins of LTC3862-2 controllers will be con- care must be taken to avoid a long ground lead on the nected directly to the input voltage. oscilloscope probe. Measure the input or output voltage Place jumper BIAS (JP12) to the AUX position for input volt- ripple by touching the probe tip directly across the V or IN age that can drop below 10V. The bias pins of LTC3862-2 V and GND terminals. See Figure 2 for proper scope OUT controllers will be connected directly to the low power probe technique. SEPIC converter, which provides regulated 10V. 1. Place jumper RUN1 (JP11) in the ON position. Place The demo board DC2006A can be used for higher than 36V jumper RUN2 (JP10) in ON position also. Note: circuit input voltages. In that case, the bias power for LTC3862-2 will not operate if jumper RUN2 (JP10) is in OFF posi- has to be limited under 36V. An external power source can tion. be used to accomplish this or the optional bias regulator 2. Place jumper BIAS (JP12) to the V position. can be used. Remove R44 and R47 resistors and install IN 0 resistors R44 and R42. 3. With power off, connect the input power supply to V IN and GND. Place jumper BIAS (JP12) to the AUX position. Since the power dissipation in linear regulator Q17 depends on the Turn the input power source on and slowly increase the size of MOSFETs, switching frequency and voltage differ- input voltage. Be careful not to exceed 36V. ence across Q17, all of the factors need to be considered NOTE: Make sure that the input voltage V does not ex- when selecting the appropriate device for Q17. Please IN ceed 36V. If higher operating voltage is required, power refer to LTC3862-2 data sheet. components with higher voltage ratings should be used. 4. Check for the proper output voltage of 50V. If there CONVERTER Eff ICIENCy is no output, temporarily disconnect the load to make DC2006A-A efficiency exceeds 96% at 12V input voltage sure that the load is not set too high. generating 50V at 10.0A and 97% at 14V input voltage, 5. Once the proper output voltages are established, adjust see Figure 3. However output (load) current should be the load within the operating range and observe the decreased at input voltages below 10V to reduce thermal output voltage regulation, ripple voltage, efficiency and stress on the converter. Figure 4 demonstrates maximum other parameters. load current, as a function of input voltage, assuming 50V output voltage. All measurements were conducted at room temperature, natural convection cooling with no air flow. dc2006aafa 2 ure roce tart