Energy Harvesting Multi-source Demoboard with Transducers (DC2080A) Brian Shaffer Applications Manager Boston Design Center Linear Technology Corporation email: bshaffer@linear.com, Phone: 978-656-3755 Hi… Thank you for participating in this Webinar today… My name is Brian Shaffer… I am the Applications Manager at Linear Technology’s Boston Design Center. The following will be a discussion about the Energy Harvesting Multi-Source Demoboard with Transducers… inside the Energy Harvesting “TO GO” Design Kit, which was developed by Linear Technology, Wurth Electronik and Energy Micro.

Outline What is the DC2080A, Energy Harvesting (EH) Multi-Source Demoboard Available Power from Typical Energy Harvesting Sources Energy Harvesting Power Management Circuits LTC3588-1: Piezoelectric Energy Harvesting Power Supply. LTC3108: Ultralow Voltage Step-Up Converter and Power Manager. LTC3105: Step-Up DC/DC Converter with Power Point Control and LDO Regulator. LTC3459: 10V Micropower Synchronous Boost Converter with Input Voltage Regulation. LTC2935-2,-4: Ultralow Power Supervisor with Power-Fail Output Selectable Thresholds. Schematic and BOM for Reference Conclusion I will describe the overall function of the Multi-source demoboard… talk about the Energy Harvesting sources the demoboard can accommodate and finish off with a review of the power management circuits and their key performance features.

Power Management Board What is the DC2080A Power Management Board for the Energy Harvesting “TO GO” DESIGN KIT Demo Circuit 2080 is the power management demoboard that will ship with the Energy Harvesting Design Kit, orderable directly from Wurth Electronik. Current versions of the kit are available with the BCB190-2, which is substantially similar to the 2080A. The fabrication documents and Demo Manual for demo circuit 2080 will be available for download within 4 weeks of this presentation. Please look for them on Linear Technology's demoboard web page and on the Wurth landing page for the Energy Harvesting “TO GO” Design Kit.

What is the DC2080A Energy Harvesting Multi-Source Demoboard with Transducers Allowable Sources PIEZOELECTRIC TRANSDUCER ELECTROMECHANICAL TRANSDUCER THERMAL ELECTRIC GENERATOR 4-20mA LOOP PHOTOVOLTAIC CELLS VIN Range 20mV @ 3.5 Ohms - 200V @ 40K Ohms VOUT Average 3.3V @ <50mA, Typically 20uA to 1mA Demo Circuit 2080A Multi-Source Demoboard contains all the power management circuits and support circuitry needed to condition Piezoelectric transducers, Electromechanical transducers, High impedance AC mains, Thermal Electric Generators, 4-20mA loop power, or Photovoltaic cells into usable energy. In addition it contains two integrated transducers, a CUI Incorporated TEG and a Panasonic AM5412 solar panel. Either of which can be used for immediate demonstration results. By selecting the correct inputs, the board accommodates input sources as low as 20mV with a source impedance of 4 Ohms… to ones that generate 200 Volts with a source impedance of 40 thousand Ohms or greater. All the power management circuits are configured to regulate at 3.3 Volts. Some of the outputs can deliver up to 50mA, but the typical average operating condition for wireless sensor nodes is 20uA to 1mA. The picture on the right hand side shows the top of the assembled board. If the integrated transducers are not needed, demo circuit 2042A, available from Linear Technology’s Web Site, is the equivalent of the bottom half. The Demo Manual and Fabrication documents are available on Linear Technology’s Demoboard web page. Top Assembly

What is the DC2080A Energy Harvesting Multi-Source Demoboard with Transducers Allowable Sources PIEZOELECTRIC TRANSDUCER ELECTROMECHANICAL TRANSDUCER THERMAL ELECTRIC GENERATOR 4-20mA LOOP PHOTOVOLTAIC CELLS VIN Range 20mV @ 3.5 Ohms - 200V @ 40K Ohms VOUT Average 3.3V @ <50mA, Typically 20uA to 1mA The bottom side of the board contains some helpful optional components. There is a large capacitor bank available to use for energy storage… or to accommodate peak current requirements during high power events such as transmitter send and receive intervals, sensor measurements or one time network joining requirements. In addition, there are unpopulated Or-ing diodes that would allow more than one Energy Harvesting source to be connected at the same time. The most powerful source or the one with the highest output voltage setting would supply the load energy. Bottom Assembly

Available Sources How Much Power is Available? The power density of Energy Harvesting Sources limit the available power they can deliver. Typical Energy Harvesting transducers for Wireless Sensor Nodes are designed to deliver an average current between 10uA and 1mA. In other applications, the transducers may be designed to deliver currents well beyond that range. From this graph, ranking the sources from most powerful to least we get: 1) Outside Sun 2) Thermal gradients 3) Inside Sun 4) Stress or Strains 5) Vibrations 6) Thermal Variations 7) Infrared 8) Biochemistry and finally 9) RF High impedance line supplies could be placed anywhere into this list, depending on the series resistance used.

LTC3588-1: Piezoelectric Energy Harvesting Power Supply (VIBRATION or High-impedance AC-sources) Key Features: Integrated rectifier converts piezo AC output to DC ( extremely low leakage ) 500nA UVLO circuit allows input cap to be charged up before DC/DC enabled – ensures reliable startup Synchronous step-down DC/DC operates over wide VIN and load current with high efficiency Overvoltage shunt protects input – dumps excess energy to GND at VIN > 20V 1uA (typ) no load ICC minimizes wasted energy at low vibration levels High impedance AC sources are conditioned by the LTC3588-1. It has an extremely low quiescent current, 950nA when regulating Vout at no load. Its DC/DC converter input voltage range is from 2.7 Volts to 18 Volts and contains an internal bridge rectifier that can handle 50mA of average current. The internal 20 Volt shunt protects the device from high impedance sources with open circuit voltages greater than its ABS Max rating. The output voltage is selectable between 1.8, 2.5, 3.3 or 3.6 Volts by changing two digital inputs.

LTC3108: TEG powered Energy Harvester Operates from inputs as low as 20mV Alternate Fixed Output Voltages Unique Resonant Power converter / Energy Harvester Auxiliary LDO Manages Energy storage between Reservoir and Main Cout or Batt Compact Step-up Transformer 3x4mm DFN or GN16 packages Unipolar TEG sources are conditioned by the LTC3108. The LTC3108 operates from as low as 20mV. In order to have good power transfer, the TEG must have a source impedance of less than 10 Ohms so that it is closely matched to the input impedance of the resonant circuit made up of T1,C8, C11,R13 and the SW pin, which is approximately 3.5 Ohms. The IC contains a power path controller that manages the Energy storage between LDO, VOUT and VSTORE. Demo circuit 2080 has the option of connecting the large capacitor bank on the bottom to either VOUT or STORE. The output voltage is selectable between 2.35, 3.3, 4.1 or 5.0 Volts by changing two digital inputs. If bipolar operation is required, where the polarity of the thermal gradient changes with time, then the LTC3109 can be used.

LTC3108 Voltage Sequencing (Measurements) Power Up Power Down VIN VLDO: 2.2V fixed VOUT: 2.35V, 3.3V, 4.1V or 5V (LTC3108 & LTC3109) VOUT: 2.5V, 3.0V, 3.7V, 4.5V (LTC3108-1) VSTORE charges up to 5.25V VSTORE VOUT VLDO This scope shot shows the power path circuirty at work, prioritizing the location of where the input energy is first stored. The priority is set as LDO then VOUT and finally VSTORE. © 2011, Linear Technology Corporation

LTC3105: supplied by diode voltage drop in 4-20mA loop Synchronous Boost Converter + LDO starts up at 250mV Includes Maximum Power Point Control (MPPC), which adjusts the peak inductor current to maintain Vin at a programmed voltage Operates from higher resistance sources than traditional boosts Uses burst-mode architecture with variable Ipk and Ivalley The LTC3105 is a Synchronous Boost Converter plus LDO that starts up with only 250mV on its input. The Maximum Power Point Control function regulates the input voltage to a set value established by the selection of the resistor on its MPPC pin. A fixed current of 10uA is sourced into this resistor and establishes the input voltage regulation point. Because of this input voltage regulation loop, the part is able to accommodate higher impedance sources than say the LTC3108 or LTC3109. It can be used for high impedance TEGs, Solar Panels or a Low voltage source, as demonstrated here with a diode drop in a 4-20mA loop.

LTC3459 supplied by solar cell >85% Efficiency over Wide Load Range Internal Synchronous Rectifier VIN Range: 1.72V to 3.3V Burst Mode Operation Inrush Current Limiting Output Disconnect in Shutdown Ultralow Quiescent (10μA) and Shutdown (<1μA) Current The LTC3459 is a 10uA Synchronous Boost Converter. The added LTC2935-4, ultra-low power supervisor with selectable thresholds, implements the MPPC function, which was built into the 3105. It can also be used for high impedance TEGs and Solar Panels from 1.72 Volts to 3.3 Volts. The inrush current limiting makes it well suited for low power sources. The output disconnect in shutdown ensures that the output capacitor will not be discharged back to the input when the source is not generating energy.

Detailed Schematic of PGOOD_LTC3459 Circuit using LTC2935-2 In addition to having the option of routing the PGOOD signal from each of the power management circuits to the header, the demo circuit provides an independent PGOOD signal and VOUT disconnect function. The RST output from the LTC2935-2 provides the independent PGOOD signal and the VOUT disconnect function via Q3. This signal is also the PGOOD signal for the LTC3459 circuit. The VOUT disconnect function is active at all times. This function is very important for many low power processors as they do not like to see slowly rising voltages below 1.5 Volts. The LTC2935-2 circuit connects VOUT to the load, when VOUT reaches 3.15 Volts and disconnects VOUT when VOUT reaches 2.25 Volts. The wide hysteresis window is generated by connecting the S2 input to the RST bar output via R35. 500nA Quiescent Current ±1.5% (Max) Accuracy over Temperature Integrated Precision Attenuators Eight Pin-Selectable Reset Thresholds Eight Pin-Selectable Power-Fail Thresholds

DC2080A Schematic Vibration or High-Impedance AC Thermal Electric Energy Storage Optional: Optional: PGOOD Pulse Circuit Thermal Electric Generator (Rs=3.5Ohms) 4-20mA Loop (Lower-Voltage Solar) This is the complete schematic of the Energy Harvester multi-Source Demoboard. The Demo manual and fabrication drawings will be available from both the Linear Technology and Wurth Electronik web sites. Optional: PGOOD Pulse Circuit ON @ 3.15Volts VSUPPLY OFF @ 2.25 Volts Lower-Voltage Solar

Linear Technology Energy Harvesting Products – Power Capability Maximum Output Power* VIN Range LTC3588-1 Iq = 950nA LTC3588-2 Iq = 1.5uA LTC3108 Iq=6uA LTC3109 Iq = 6uA LTC3105 Iq =24uA LTC3388-X Iq = 720nA LTC4071 Iq = 550nA UVLO_Rising<VIN<=18V 0.36W (3.6V*100mA) 0.5W (5.0V*100mA) Vin>18V 90mW (18V*5mA) 2.7V<VIN<=20V 0.25W (5V@50mA) VIN=0.6V 10mW (2.8mA*3.3V) 15mW (4.5mA@3.3V) Vcc<=Vshunt 50mA@Vshunt Vin=3V 500mW (Vout=5V) Vin=1V 290mW This slide contains the power capabilities of additional components to consider when doing ultra-low power designs. The LTC3388 is a 20 Volt, 720nA Synchronous Buck converter. The LTC4071 is a 50mA shunt Li-Ion battery charger with low battery disconnect. The quiescent current of the LTC4071 is 500nA while operational and draws only pico-amps from the battery when the battery hits its low battery disconnect threshold. *Provided the source is capable of delivering the required power to overcome the inefficiency of the power converter

LTC Energy Harvesting Solutions Energy source Transducers LTC Power Management ICs Typical POUT @ VOUT = 3.3V Maximum POUT Indoor Solar (200lux – 1000lux) Photovoltaic Cells (100cm2) LTC3105 LTC4071 LTC3129 LTC3459 100uW – 1mW >100mW Outdoor Solar (1000lux – 50000lux) LTC3588 1mW – 100mW Thermal (10oC – 30oC dT) TEGs (100cm3) LTC3108 LTC3109 200uW – 1.4mW >10mW Vibration (Piezo: 0.1g – 1g) (EM: 0.025g – 0.5g) Piezoelectric (30cm2) Electromechanical (200cm3) 50uW – 500uW 500uW – 10mW This slide contains similar information but with the part numbers organized by Energy Harvester Source.

Conclusion The DC2080A Multi-Source Demoboard contains power management circuits and support circuitry to condition: Piezoelectric Electromechanical High impedance AC mains Thermal Electric Generators 4-20mA loop power Photovoltaic cells If the Integrated Transducers are not needed consider the DC2042A The Multi-Source Demoboard contains power management circuits and support circuitry to condition: Piezoelectric transducers Electromechanical transducers High impedance AC mains Thermal Electric Generators 4-20mA loop power and Photovoltaic cells If the Integrated Transducers are not needed consider the DC2042A… Thank you for attending this webinar today. Thank You