QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286 48V OUTPUT BOOST CONVERTER LTC3862EGN, LTC3862EGN-1 DESCRIPTION Demonstration circuit 1286A is DC/DC boost converter The demonstration circuit can be easily modified to gen- featuring the LTC 3862EGN constant frequency current erate different output voltages. Please consult LTC fac- mode boost controller. The DC1286A-A operates over 5V tory for details. to 36V input and provides 2A-5A of output current at The DC1286A has small circuit footprint. It is a high per- 48V output. The DC1286A-B operates over 8V to 36V formance and cost effective solution for Telecom, Auto- input and provides 3A-5A of output current at 48V out- motive and Power Over Ethernet applications. put. The 200kHz constant frequency operation results in small and efficient circuit. The converter provides high output voltage accuracy (typically 3%) over wide load Design files for this circuit board are available. Call range with no minimum load requirement. the LTC factory. PowerPath is a trademark of Linear Technology Corporation Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage I = 0A to 2A OUT DC1286A-A 5V DC1286A-B 8V Maximum Input Voltage I = 0A to 5A 36V OUT V V = 12V, I = 3A 48V 3% OUT IN OUT Typical Output Ripple V V = 12V, I = 4A 400mV OUT IN OUT PP Nominal Switching Frequency 200kHz QUICK START PROCEDURE Demonstration circuit 1286A is easy to set up to evalu- 2. Check the Vcc Bias voltage-setting jumper JP5. Move ate the performance of the LTC3862. For proper meas- it into Vin position if required. urement equipment setup refer to F igure 1 and follow 3. Turn the input power source on and slowly increase the procedure below: the input voltage. Be careful not to exceed 36V. NOTE: When measuring the input or output voltage rip- NOTE: Make sure that the input voltage Vin does not ple, care must be taken to minimize the length of oscil- exceed 36V. If higher operating voltage is required, loscope probe ground lead. Measure the input or output power components with higher voltage ratings should voltage ripple by connecting the probe tip directly across be used. Also, Jumper JP5 will have to be moved to the VIN or VOUT and GND terminals as shown in 12V position. Figure 2. 4. Check for the proper output voltage of 48V. 1. With power off, connect the input power supply to Vin If there is no output, temporarily disconnect the load and GND. to make sure that the load is not set too high. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286 48V OUTPUT BOOST CONVERTER OPTIONAL BIAS CIRCUIT 5. Once the proper output voltage is established, adjust the load and observe the output voltage regulation, ripple voltage, efficiency and other parameters. The demo board DC1286A can be used for boosting higher input voltages as well. In that case, the bias power for LTC3862 has to be limited under 36V. An ex- ternal power source can be used to accomplish this or the optional bias regulator can be used by moving JP4 to 12V position. Since the power dissipation in bias regulator Q5 depends on the size of MOSFETs, switching frequency and voltage difference across Q5 all of the factors need to be considered when selecting the appro- priate device for Q5. Please refer to LTC3862 data sheet for bias power requirements. Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2