LTC3108EDE DEMO CIRCUIT 1582B QUICK START GUIDE LTC3108EDE/ LTC3108EDE-1 Ultralow Voltage Step-Up Converter and Power Manager DESCRIPTION Demonstration Circuit 1582B featuring the LTC3108 is The Demonstration Circuit has been set up with a storage a highly integrated DC/DC converter optimized for capacitor that makes it easy to evaluate the general func- harvesting and managing energy from extremely low tionality of the circuit. The lower value capacitor allows input voltage sources such as thermoelectric genera- for a fast charge time but limits the pulsed energy that tors (TEG). The step-up topology operates from input can be drawn from it. Space is provided, and alternate voltages as low as 20mV. part footprints have been built into the PCB to allow ex- perimentation with larger capacitors for more energy The DC 1582B Demonstration Circuit has been optimized storage. In a typical application, the larger output capaci- for low start-up voltage with a 100:1 turns ratio trans- tors may be used. Refer to the datasheet for more in- former. For application where it is desirable to trade-off formation including equations to properly size the output a higher start-up voltage for higher current, a lower turns capacitors for a given application. ratio transformer can be used. Refer to the LTC3108 datasheet for more information. The LTC3108 is available in two versions, the only differ- ence being the VOUT and VOUT2 output voltages. Refer The LTC3108 is designed to accumulate and manage to the datasheets for more information. energy over a long period of time to enable short bursts of power to be used to acquire and transmit data. The Design files for this circuit board are available. Call burst must occur at a low enough duty cycle such that the LTC factory. the total output energy during the burst does not exceed L, LTC, LTM, LT, Burst Mode, are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. the average source power integrated over the accumula- tion time between bursts. TABLE 1. Typical Specifications (25C) 50mV-400mV (Typical no load start-up = 20mV) Input Voltage Range VLDO 2.2V VOUT Jumper Selectable from 2.35 to 5.0V VOUT2 Switched Output, VOUT2=VOUT VSTORE 5.25V 1 LTC3108EDE QUICK START PROCEDURE Using short twisted pair leads for any power connections and with all loads and power supplies off, refer to Fig- ure 1 for the proper measurement and equipment setup. The Power Supply (PS1) should not be connected to the circuit until told to do so in the procedure below. Two versions of the demo board are available. Assembly build A uses the LTC3108EDE while Assembly build B uses the LTC3108EDE-1. The only difference is the VOUT and VOUT2 voltages. When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VCC or VOUT and GND terminals. See Figure 2 for proper scope probe technique. 1. Jumper, Power Supply and LOAD Settings to start: PS1= OFF LOADS = OFF JP1 (VOUT2) = ON JP2= VAUX JP3 = VAUX 2. Turn on PS1 and slowly increase voltage until the voltage at VIN is 50mV. Monitor input current. If input current exceeds 50 mA turn off PS1 and look for shorts. 3. Confirm VLDO = 2.2V 4. Increase Vin = 100mV 5. Set LOAD on VLDO to 50A. Set LOAD on VOUT = 25 A. Set LOAD on VOUT2 = 25 A. 6. For the A version: Verify VLDO = 2.2V, VOUT 5.0V, VOUT2 5.0V, and VSTORE 5.2V 7. For the B version: Verify VLDO = 2.2V, VOUT 4.5V, VOUT2 4.5V, and VSTORE 5.2V The board is now ready for operation. The voltage on VOUT and VOUT2 can be modified by changing jumpers JP2 and JP3. The jumper combinations are shown on the demo board. Several variations of this design are possible, including increasing the energy storage by populating C7, or C9. Please refer to the datasheet for design equations. 2