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PicoScope® PC- OSCILLOSCOPES For every application there’s a PicoScope • Bandwidth from 5 MHz to 1 GHz • Sampling from 10 MS/s to 5 GS/s • Memory from 8 ks to 2 GS PICOSCOPE 6000 SERIES Ultimate performance, now USB 3.0 PICOSCOPE 5000 SERIES Flexible resolution oscilloscopes PICOSCOPE 4824 8 Channels, high resolution PICOSCOPE 3400 SERIES High-performance oscilloscopes ALL MODELS INCLUDE FULL SOFTWARE AND 5 YEAR WARRANTY. SOFTWARE INCLUDES MEASUREMENTS, SPECTRUM ANALYZER, SDK, ADVANCED TRIGGERS, COLOR PERSISTENCE, SERIAL DECODING (CAN, LIN, RS232, I²C, I²S, FLEXRAY, SPI), MASKS, MATH CHANNELS, ALL AS STANDARD, WITH FREE UPDATES. PicoScope software is now available for Linux in full release, and for MAC in beta www.picotech.com/PS340 The LTC3331’s EH power supply, consisting of a full-wave bridge rectifier accommodating AC or DC inputs and a high efficiency synchronous buck converter, harvests energy from piezoelectric (AC), solar (DC) or magnetic (AC) sources. A 10mA shunt allows simple charging of the battery with harvested energy while a low battery disconnect function protects the battery from deep discharge. The rechargeable battery powers a synchronous buck-boost converter that operates from 1.8V to 5.5V at its input and is used when harvested energy is not available to regulate the output whether the input is above, below or equal to the output. The battery charger IC has a very important power management feature that cannot be overlooked when dealing with micro power sources. The LTC3331 incorporates logical control of the battery charger such that it will only charge the battery when the energy harvested supply has excess energy. Without this logical function the energy harvested source would get stuck at startup at some non-optimal operating point and not be able to power the intended application through its startup. The chip automatically transitions to the battery when the harvesting source is no longer available. This has the added benefit of allowing the battery operated WSN to extend its operating life from 10 years to over 20 years if a suitable EH power source is available at least half of the time, and even longer if the EH source is more prevalent. A supercapacitor balancer is also integrated allowing for increased output storage. The LTC3129 is a synchronous buck-boost converter that delivers up to 200mA of continuous output current from a wide variety inputs sources. These include single or multiple cell batteries as well as solar panel and supercapacitor inputs. Its 2.42V to 15V input range and 1.4V to 15.75V output range provides a regulated output with inputs above, below or equal to the output. The low noise buck-boost topology incorporated in the LTC3129 provides a continuous transition through all of the operating modes, making it ideal for EH applications that must maintain a constant output voltage even as the input source voltage declines below the output – see figure 2. The chip includes programmable maximum power point control (MPPC) capability which ensures maximum power extraction from non-ideal power sources such as photovoltaic cells. Quiescent current of only 1.3μA makes it ideal for alwayson and energy harvesting applications in which extended battery run-time is of primary importance. Its constant 1.2MHz switching frequency ensures low noise and high efficiency while minimizing the size of the external components. Conclusion Even though wearable applications with energy harvesting systems will have a broad range of power levels for their correct operation, from microwatts to great than 1W, there are many power conversion ICs available for selection by the system designer. However, it is at the lower end of the power range, where nanoamps of currents need to be converted. That’s where the choice becomes limited. Fortunately, the LTC3331 energy harvester and battery life extender, along with the LTC3129 low power synchronous buck-boost converter provide extremely low quiescent currents, making them ideal for a broad range of low power applications. Quiescent currents of less than 1.3μA prolong battery life for keep-alive circuits in portable and wearable electronics, while allowing a new generation of EH applications. This is good news indeed since we are moving toward the inflexion point for energy harvesting and the internet of things. www.electronics-eetimes.com Electronic Engineering Times Europe September 2014 27


EETE SEP 2014
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