DEMO MANUAL DC2151A LTC3331EUH Nanopower Buck-Boost DC/DC with Energy Harvesting Battery Charger Description Demonstration Circuit DC2151A is a nanopower buck- A 10mA shunt allows simple battery charging with harvest boost DC/DC with energy harvesting battery charger energy while a low battery disconnect function protects the featuring the LTC 3331. The LTC3331 integrates a high battery from deep discharge. A supercapacitor balancer voltage energy harvesting power supply plus a DC/DC is also integrated, allowing for increased output storage. converter powered by a rechargeable cell battery to create Voltage and current settings for input and output as well a single output supply for alternative energy applications. as the battery float voltage are programmable via pin- The energy harvesting power supply, consisting of an strapped logic inputs. integrated low-loss full-wave bridge with a high voltage The LTC3331EUH is available in a 5mm 5mm 32-lead buck converter, harvests energy from piezoelectric, solar QFN surface mount package with exposed pad. or magnetic sources. The rechargeable cell input powers a buck-boost converter capable of operating down to 1.8V at its input. Either DC/DC converter can deliver energy to L, 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 Drive, a single output. The buck operates when harvested energy FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode Dimming, No is available, reducing the quiescent current drawn on the Latency , No Latency Delta-Sigma, No RSENSE, Operational Filter, PanelProtect, PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO battery to essentially zero. The buck-boost takes over are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. when harvested energy goes away. Boar D p Buck Efficiency vs I LOAD 100 90 80 70 60 50 40 V = 1.8V OUT 30 V = 2.5V OUT 20 V = 3.3V OUT V = 5V OUT 10 V = 6V, L = 22H, DCR = 0.19 IN 0 1 10 100 1m 10m 100m I (A) LOAD 3331 G34 Figure1. DC2151A Demoboard Figure2. Typical Efficiency of DC2151A dc2151af 1 EFFICIENCY (%) hotoDEMO MANUAL DC2151A p s Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN MAX UNITS V Input Voltage Range 3.0 to 18.0 V IN V 1.8V Output Voltage Range OUT0=0, OUT1=0, OUT2=0 1.728 to 1.872 V OUT V 2.5V Output Voltage Range OUT0=1, OUT1=0, OUT2=0 2.425 to 2.575 V OUT V 2.8V Output Voltage Range OUT0=0, OUT1=1, OUT2=0 2.716 to 2.884 V OUT V 3.0V Output Voltage Range OUT0=1, OUT1=0, OUT2=0 2.910 to 3.090 V OUT V 3.3V Output Voltage Range OUT0=0, OUT1=0, OUT2=1 3.200 to 3.400 V OUT V 3.6V Output Voltage Range OUT0=1, OUT1=0, OUT2=1 3.492 to 3.708 V OUT V 4.5V Output Voltage Range OUT0=0, OUT1=1, OUT2=1 4.365 to 4.635 V OUT V 5.0V Output Voltage Range OUT0=1, OUT1=1, OUT2=1 4.850 to 5.150 V OUT V 3.45V Float Voltage Range FLOAT1=0, FLOAT=0 3.381 to 3.519 V BAT V 4.00V Float Voltage Range FLOAT1=0, FLOAT=1 3.920 to 4.080 V BAT V 4.1V Float Voltage Range FLOAT1=1, FLOAT=0 4.018 to 4.182 V BAT V 4.2V Float Voltage Range FLOAT1=1, FLOAT=1 4.116 to 4.284 V BAT o p Refer to the block diagram within the LTC3331 data sheet a total drop of about 800mV at typical piezo-generated for its operating principle. currents, but is capable of carrying up to 50mA. The LTC3331 combines a buck switching regulator and When the voltage on V rises above the UVLO rising IN a buck-boost switching regulator to produce an energy threshold the buck converter is enabled and charge is harvesting solution with battery backup. The converters are transferred from the input capacitor to the output capaci- controlled by a prioritizer that selects which converter to tor. When the input capacitor voltage is depleted below use based on the availability of a battery and/or harvestable the UVLO falling threshold the buck converter is disabled. energy. If harvested energy is available, the buck regulator These thresholds can be set according to Table 4 of the is active and the buck-boost is off. With a battery charger data sheet which offers UVLO rising thresholds from 4V and a supercapacitor balancer and an array of different to 18V with large or small hysteresis windows. configurations, the LTC3331 suits many applications. Two internal rails, CAP and V , are generated from V and IN2 IN The synchronous buck converter is an ultralow quiescent are used to drive the high side PMOS and low side NMOS current power supply tailored to energy harvesting applica- of the buck converter, respectively. Additionally the V IN2 tions. It is designed to interface directly to a piezoelectric rail serves as logic high for output voltage select bits UV or alternative A/C energy source, rectify and store the har- 3:0 . The V rail is regulated at 4.8V above GND while IN2 vested energy on an external capacitor while maintaining a the CAP rail is regulated at 4.8V below V . These are not IN regulated output voltage. It can also bleed off any excess intended to be used as external rails. Bypass capacitors input power via an internal protective shunt regulator. should be connected to the CAP and V pins to serve IN2 An internal full-wave bridge rectifier, accessible via AC1 as energy reservoirs for driving the buck switches. When and AC2 inputs, rectifies AC sources such as those from V is below 4.8V, V is equal to V and CAP is held IN IN2 IN a piezoelectric element. The rectified output is stored on at GND. V is an internal rail used by the buck and the IN3 a capacitor at the V pin and can be used as an energy buck-boost. When the LTC3331 runs the buck, V will IN IN3 reservoir for the buck converter. The bridge rectifier has be a Schottky diode drop below V . When it runs as a IN2 buck-boost V is equal to BAT. IN3 dc2151af 2 rinciple perating ummary erformance