DEMO MANUAL DC2006A-B LTC3862-2 High Power, High Voltage Step-Up Converter Description Demonstration circuit 2006A-B is a multiphase high power, The LTC3862-2 is a multiphase step-up (boost) DC/DC high voltage step-up DC/DC converter featuring two the controller that delivers high output power in a compact LTC 3862-2 boost controllers. This demo board converts footprint. Up to 12 power stages can be paralleled and a 6V to 36V input voltage to a 120V output at up to 2.0A clocked out-of-phase to minimize input and output filtering with two stages. The first stage converts the input voltage requirements. It has a 5.5V to 36V input voltage range and to 50V. The second stage converts the 50V to 120V and an output voltage range that is dependent on the choice each stage uses one LTC3862-2. of external components. The DC2006A-B supports three ways of biasing the The LTC3862-2 utilizes peak current mode architecture for LTC3862-2 controllers ICs by directly from the input easy loop compensation and multiphase operation with voltage, or from a low power switching power supply or very accurate phase-to-phase current matching. The fixed from an LDO regulator. operating frequency can be set with a single resistor over a 75kHz to 500kHz range or can be synchronized to an An onboard SEPIC power supply can provide a stable 10V external clock over a 50kHz to 600kHz frequency range. bias voltage for both LTC3862-2 controllers over the wide A current sense resistor is used in each phase to provide varying input voltage. This allows the use of either logic a precise cycle-by-cycle current limit. The powerful on- level or standard level MOSFETs, even when the input board gate drivers minimize switching losses and allow voltage drops below the 10V set-point, which is useful in the use of multiple MOSFETs in parallel for very high wide varying input applications. current applications. An onboard LDO regulator can be selected for biasing the Design files for this circuit board are available at LTC3862-2 controllers which simplifies the design and is DEMO MANUAL DC2006A-B 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 LTC3862-2 controllers. Place jumper BIAS (JP12) to the follow the procedure below: V position for input voltage above 10V, but below 36V. IN NOTE. When measuring the input or output voltage ripple, In this case bias pins of LTC3862-2 controllers will be care must be taken to avoid a long ground lead on the connected 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. input voltages. In that case, the bias power for LTC3862 -2 2. Place jumper BIAS (JP12) to the V position. has to be limited under 36V. An external power source can IN be used to accomplish this or the optional bias regulator 3. With power off, connect the input power supply to V IN can be used. Remove R44 and R47 resistors and install and GND. 0 resistors R44 and R42. Turn the input power source on and slowly increase the Place jumper BIAS (JP12) to the AUX position. Since the input voltage. Be careful not to exceed 36V. power dissipation in linear regulator Q17 depends on the NOTE: Make sure that the input voltage V does not ex- size of MOSFETs, switching frequency and voltage differ- IN ceed 36V. If higher operating voltage is required, power ence across Q17, all of the factors need to be considered components with higher voltage ratings should be used. when selecting the appropriate device for Q17. Please refer to LTC3862-2 data sheet. 4. Check for the proper output voltage of 120V. If there is no output, temporarily disconnect the load to make sure that the load is not set too high. Take all the precautions CONVERTER Eff ICIENCy needed to work with high 120V output voltage. DC2006A-B efficiency reaches 92% at 12V input voltage 5. Once the proper output voltages are established, adjust generating 120V at 2.0A and 93% at 14V input voltage, the load within the operating range and observe the see Figure 3. However, output current should be decreased output voltage regulation, ripple voltage, efficiency and at input voltages below 11V to reduce thermal stress on other parameters. the converter. Figure 4 demonstrates maximum output current, as function of input voltage, assuming 120V output voltage. All measurements were conducted at room temperature, natural convection cooling with no air flow. dc2006abfa 2 ure roce tart