DEMO CIRCUIT 1411A LTC3787 QUICK START GUIDE LTC3787 High Efficiency PolyPhase Synchronous Boost Converter DESCRIPTION Demonstration circuit DC1411 is DC/DC boost converter The DC1411 has small circuit footprint. It is a high per- featuring the LTC3787 constant frequency current mode formance and cost effective solution for Telecom, Auto- boost controller. The DC1411A operates over 5V to 24V motive and Power Over Ethernet applications. input and provides 6A to 16A of output current as shown in figure 3. The 350kHz constant frequency operation re- Design files for this circuit board are available. Call the sults in small and efficient circuit. The converter provides LTC factory. high output voltage accuracy (typically 3%) over wide L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy load range with no minimum load requirement. The dem- Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode Dim- onstration circuit can be easily modified to generate dif- ming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, Ul- ferent output voltages. Please consult LTC factory for de- traFast and VLDO are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. tails. Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage I = 0A to 6A 5V OUT Maximum Input Voltage I = 0A to 16A 24V OUT V V = 5V to 24V, I = 0A to 6A 24V 3% OUT IN OUT Typical Output Ripple V V = 5V to 24V, I = 6A 200mV OUT IN OUT PP Nominal Switching Frequency 350kHz QUICK START PROCEDURE Demonstration circuit DC1411 is easy to set up to evalu- 3. Turn the input power source on and slowly increase ate the performance of the LTC3787. For proper meas- the input voltage. Be careful not to exceed 24V. urement equipment setup refer to Figure 1 and follow the NOTE: Make sure that the input voltage Vin does procedure below: not exceed 24V. If higher operating voltage is re- NOTE: When measuring the input or output voltage quired, power components with higher voltage ratings ripple, care must be taken to minimize the length of should be used. oscilloscope probe ground lead. Measure the input or 4. Set the input voltage to 6V and check for the proper output voltage ripple by connecting the probe tip di- output voltage of 24V. If there is no output, temporar- rectly across the VIN or VOUT and GND terminals as ily disconnect the load to make sure that the load is shown in Figure 2. not set too high. 1. With power off, connect the input power supply to 5. Once the proper output voltage is established, adjust Vin and GND. the load and observe the output voltage regulation, 2. Check the Vcc Bias voltage-setting jumper JP5. Move ripple voltage, efficiency and other parameters. it into Vin position if required. 1 GND VIN LTC3787 Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple CHANGING THE OUTPUT VOLTAGE To set the output voltage lower than 24V, change the mode are due to the current sense resistors, induc- bottom voltage divider resistors connected to tors and output MOSFETs DC resistance. LTC3787 FB pin (see the schematic on page 4). To get higher than 24V output voltage MOSFETs and capacitors with higher voltage ratings may be re- quired. Please contact LTC factory for details. Note that the output voltage will start following the input voltage when input voltage is greater than the voltage set by the voltage divider. In this mode (wire mode) the synchronous output rectifier MOSFET is turned continuously ON. The only losses in this 2