COVER ST RY R STORY


FEAT RE FEA energy harvesting power supply,


consumption), to determi en battery run time


 Small, light weight and low profile solution footprints


 Advanced packaging for improved thermal performance and space


Fortunately, recent produ efficiency


introductions from Analog


Devices’ Power ct


by Linear Group, such as the ultra-low Iq LTC3388/-x buck regulator, the


nanopower LTC3331 energy harvesting regulator and LTC3335 buc k-boost converter with integrated coulomb counter have most of these attributes. The LTC3388 is an ultralow quiescent current synchronous buck converter which can deliver up to 50mA of


continuous output current from a 2.7V to 20V input supply. The LTC3388’s no-load operating current of only 720nA makes it ideal for a wide range of battery- powered and low quiescent power applications such as “keep -alive ” supplies and wearables. Its hysteretic synchronous rectification optimises efficiency over a wide range of load currents. It also provides over 90% efficiency for loads ranging from 15uA to 50mA and only requires 720nA of no load quiescent current in regulation, thereby extending battery l The combination of a 3m


m x 3mm DFN ife.


package (or MSOP-10) and only five external components affords a very simple and compact soluti on footprin t for a wide array of low power


applications. Figure 1 shows a typical LTC3388 application circui t .


NANOPOWER QUIESCENT CURRENT ICS – LTC3335 AND LTC333LTC3331 The LTC3335 is a nanopower high efficiency synchronous buck-boost converter with an onboard precision coulomb counter that delivers up to 50mA of continuous output current. With only 680nA of quiescent current and programmable peak input currents from as low as 5mA up to 250mA, the device is ideally suited for a wide variety of low power battery applications, such as those found in wearables and IoT devices. Its 1.8V to 5.5V input range and 8 user-selectable outputs between 1.8V and 5V provide a regulated output supply with an input voltage above, below or equal to the output. ,


NANOPOWER QUIESCEN CURREN S – LT


L C3335 A D L


In addition the device’s i ntegrated precision (±5% battery discharge


measurement accuracy) coulomb counter provides accurate monitoring of


accumulated battery discharge in long- life non-rechargeable battery-powered applications, which in many cases have extremely flat battery discharge curves.


/ ELECTRONICS ELECTRONICS


Typical applications include wireless sensors remote monitors and Power by Linear’s Dust Networks SmartMesh systems. The LTC3335 includes four internal low RDSON MOSFETs and can deliver efficiencies of up to 90%.


, ,


Other features include a programmable discharge alarm threshold, an I2C interface for accessing coulomb count and device programming, a Power Good output, and 8 selectable peak input currents from 5mA up to 250mA to accommodate a wide range of batter y types and sizes. The LTC3335 is available with an operating range from -40°C


enhanced, 20-lead 3mm x 4mm QFN package. Figure 2 shows the typical LTC3335 application circuit.


The LTC3331 is a complete energy harvesting solution that delivers up to 50mA of continuous output current to extend battery life when harvestable energy is available. A simple 10mA shunt enables charging of a rechargeabl e battery with harvested energy while a low battery disconnect function protects the battery from deep discharge. It requires only 200nA of supply current from the battery when providing regulated power to the load from harvested energy and only 950nA operating when powered from the battery under no-load conditions.


The LTC3331 integrates a high voltage energy harvesting power supply, a battery charger, and a synchronous buck-boost DC/DC converter, creating a single continuous regulated output for energy harvesting applications such as those in wireless sensor networks. The


Figure 2: Figure 2:


LTC3335 simplified application schematic


LTC3335 simplified application schematic


consisting of a full-wave bridge rectifier accommodating AC or DC inputs and a high efficiency buck converter, harvests energy from piezoelectric (AC), solar (DC), or magnetic (AC When harvested ene


ATUR E


rgy is not available, ) sources.


the rechargeable battery input powers a buck-boost converter that operates over the full battery voltage range up to 4.2V and can regulate whether the input is above, below or equal to the output. The LTC3331 automatically transitions to the battery when the harvesting source is n o longer available. The LTC3331’s energy harvesting inputs operate from a voltage range of 3V to 19V AC or DC, making the device ideal for a wide array of


to 125°C in a thermally junction temperature


piezoelectric, solar, or magnetic energy sources. Its input undervoltage lockout threshold settings are programmable between 3V and 18V, enabling the application to operate the energy harvesting source at its peak power transfer point. Other features includ e pin-programmable output voltages and buck-boost peak current limits, a supercapacitor balancer, and an input protective shunt. The LTC3331 is available in a thermally enhanced 5mm x 5mm QFN package. Figure 3 shows the typical LTC3331 application circuit.


The smart wearables market has


exploded in recent years and includes a wide variety of products for the health & fitness, medical, infotainment, military and industrial application spaces A ne w wave of products, including sensor-filled medical health and wellness wearables can monitor key bio-stats such as heart rate and blood pressure outside of a medical facility, resulting in opportunities for more pro-active, healthier lifestyles. The core architecture for a smart


. Figure 3: Figure 3:


LTC3331 ty application


LTC3331 typical application circuitt


circui pical


wearable device depends on the product type, but essentially consists of a micro- controller, MEMS sensor(s), wireless connectivity, battery and suppor t electronics. Powering a low-current wearable device can p challenging; however,


Power by Linear rove very


offers a portfolio of leading-edge products capable of very high performance at low power levels.


Devices like the ultra-low Iq LTC3388 energy harvesting buck regulator, and for nanopower consumption, the LTC3331 energy harvesting buck regulator & LTC3335 buck-boost regulator with integrated coulomb counter can greatl y simplify and improve the performance of smart wearable devices.


www.linear.com www.analog.com 01628 477 066


ELEC RO ELECTRONICS CS


Analog Devices Ltd. www.linear.com www.analog.com


| DECEMBER/JANUAR 201 ECEMBER/J


JANUARY 2018 13


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