25.07.2014

Dc quiescent power

EM Microelectronic is promoting its EM8500 energy harvester chip, claimed to be the lowest power photovoltaic harvester.
The Swiss chip company, which has its own fab, is owned by Swatch and has a background in ultra-low power electronics. The power figures, it claims, are the lowest in the industry for those voltages, meaning it will work off smaller solar cells than chips from competitors. However, it will not start-up on, for example, 20mV, which is what Linear Tech’s LTC3107 can do. That said, EM8500 can work form TEGs as well as photovoltaic cells, and on-chips are two peak power tracking algorithms – one for solar cells and one for TEGs. These two modes, like other modes in the chip, can be set by programming the built-in eeprom. Quiescent current is 15nA in the lowest power mode, and 125nA with the dc-dc converter running. One of novel feaure is having two capacitive storage elements – a large one and a small one.
So that operating voltage is reached quickly, input power is initially sent to the small capacitor, and only when that one is charged to the larger one – which can also be a supercap or rechargeable battery. The Baron on Folk-Lore Flummoxed: ‘"This time all the analysts are forecasting a flat year.
Electronics Weekly is the market leading and longest-established electronics magazine, read in print and online by key decision makers throughout the industry for more than 50 years. We won't be using the pre-amplifier transistors in this amplifier, but they may be documented in an upcoming project. Modifying and cutting down the module's original aluminum case so it can be mounted to the front-panel. A solder terminal strip was added on the lower-right for centralizing the DC input power connections. This is first of several modifications which will need to be done in order to use the amplifier.
To generate this voltage, we'll isolate and use a 78M05 voltage regulator on the amplifier circuit board. Note that you'll need to follow the traces on the output of the 78M05 and remove three series resistors, as shown above. Solder a jumper wire from the YELLOW dot (+28 VDC) to the two parallel 4.7 ohm resistors on the input of the 78M05. You'll need to cut the trace were the arrow is pointing to isolate it from that feed-through via. Connect good 50 ohm loads to the input and output of the amplifier and apply a clean source of +28 VDC power through an accurate current meter. Rear view of the front-panel showing the DC input wiring and fuse, and the panel-mounted N connector for the RF output.
Device offers protection for current limit, overload and output short circuit, and over-temperatureThis post sponsored by Texas Instruments.The UCC28880 integrates the controller and a 700-V power MOSFET into one monolithic device.
The LTC3129 employs an ultralow noise, 1.2MHz PWM switching architecture that minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. Additional features include a power good output, less than 10nA of shutdown current and thermal shutdown.
The LTC3129 is available in thermally enhanced 3mm × 3mm QFN and 16-lead MSOP packages. Please login to your MyLinear account for notifications of datasheet updates, new document releases and LTspice model announcements for your favorite products. LTspice® IV is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900. Energy harvesting with a photovoltaic cell requires an efficient dc-dc converter that operates with very low voltage inputs and whose output can charge an external battery.
Power Systems Design (PSD) empowers global innovation for the power electronic design engineering community. Linear Technology announced the LT8631, a 1A, 100V input capable synchronous step-down switching regulator. The LT8631a€™s Burst Mode operation offers ultralow quiescent current, making it well suited for applications such as automotive a€?always-ona€? systems, which need to extend operating battery life. The LT8631 utilizes internal top and bottom high efficiency power switches with the necessary boost diode, oscillator, control and logic circuitry integrated into a single die.
This would give Linear Tech the edge when working from small thermoelectric generators (TEGs). Electronics Weekly is at the heart of the electronics industry and is reaching an audience of more than 120,000 people each month. Additionally, it integrates a high-voltage current source, enabling start-up and operation directly from the rectified mains voltage.   The low quiescent current of the UCC28880 allows for excellent efficiency. It includes an accurate RUN pin threshold to allow predictable regulator turn-on and a maximum power point control (MPPC) capability that ensures maximum power extraction from non-ideal power sources such as photovoltaic panels.


For fixed output voltage options, see the functionally equivalent LTC3129-1, which eliminates the need for an external feedback divider. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. The LT8631a€™s unique design maintains a minimum dropout voltage, enabling it to operate with duty cycles up to 99%.
Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 10mVP-P.
The XCL210 series is sutiable for applications that require a low quiescent current such as wearable devices, healthcare devices, Bluetooth low-energy devices, and energy harvesting.
In Power Save Mode, the TPS62743 extends the light load efficiency down to a load current range of 10µA and below. With the UCC28880, the most common converter topologies, such as buck, buck-boost, and flyback, can be built using a minimum number of external components.
For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.
Its resistor programmable 100kHz to 1MHz frequency range and synchronization capability enable optimization between efficiency and external component size. Special design techniques enable high efficiency over a wide input voltage range, and the LT8631a€™s current mode topology enables fast transient response and excellent loop stability. The device incorporates a soft-start feature for controlled startup of the power stage, minimizing the stress on the power-stage components. This eliminates the need to for an ac power line-based recharging circuit, which may be impractical in a remote application.
Its internal high efficiency switches deliver up to 1A of continuous output current to voltages as low as 0.8V. The LT8631a€™s 20-lead TSSOP package with high voltage lead spacing ensures a compact, thermally efficient footprint for high voltage applications.
Other features include robust short-circuit protection, a power good flag, output voltage tracking and thermal protection. Pricing starts at $3.60 each in 1,000 piece quantities and all versions are available from stock. It generates its own internal low-voltage supply (5 V referenced to the device’s ground) from the integrated high-voltage current source. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application. Typically, these applications require very low average power, but can require periodic pulses of higher load current.
It may be used for applications such as AC-to-DC power supplies, metering, home automation, infrastructure SMPS, appliances, and LED drivers. The Linear Technology LTC3105 is intended for these types of energy harvesting applications. It is optimized to provide a low-output voltage ripple and low noise using a small output capacitor.
Once the input voltage comes close to the output voltage, the device enters the No Ripple 100% mode to prevent an increase of output ripple voltage.
In this operation mode, the device stops switching and turns the high side MOSFET switch on. An integrated maximum power point controller (MPPC) optimizes performance from photovoltaic (PV) cell inputs.
The internal coil simplifies the board layout, and contributes to space saving on the board and shortening of development time.
The LT3105's 3mm ? 3mm DFN package (or MSOP-12) and very small external components offer a compact solution for energy harvesting.
Burst Mode, with proprietary self-adjusting peak current, optimizes converter efficiency and output voltage ripple over all operating conditions. You can adjust the LDO with a voltage divider consisting of a resistor from the LDO pin to FBLDO then another resistor to GND. As an alternative, you can connect the FBLDO pin to GND to deliver a nominal 2.2V output for the LDO.
An optional 22pF feed-forward capacitor from VOUT to FB (paralleling the 1020 k? resistor in Fig. However, continuous operation above the specified maximum operating junction temperature may impair reliability. This aids PV cells that can become overloaded if inrush current is not limited during power converter start-up. In addition, output disconnect isolates VOUT from VIN while in shutdown, resulting in 4µA quiescent current. This pin incorporates an internal 2M? pull-up resistor, which enables the converter when not controlled by an external circuit. At low system voltages (VIN and VAUX), the shutdown pin thresholds are as low as 50mV from the voltage rails.


Once VAUX reaches approximately1.4V, the converter leaves start-up mode and enters normal operation. Maximum power point control is not enabled during start-up, however, the currents are internally limited to sufficiently low levels to allow start-up from weak input sources. While the converter is in start-up mode, the internal switch between AUX and VOUT remains disabled and the LDO is disabled. After ending the shutdown event, the LDO remains in reverse-blocking mode until VAUX rises above the LDO voltage. If VAUX becomes higher than required to maintain LDO regulation, charge is transferred from the AUX output to the VOUT output. If VAUX falls too low, current redirects to the AUX output, instead of being used to charge the VOUT output. Once VOUT rises above VAUX, the IC enables an internal switch to connect these two outputs together.
This switch remains on until inductor current drops below the valley current limit and the cycle is repeated.
When VOUT reaches the regulation point, the N- and P-channel MOSFETs connected to the SW pin are disabled and the converter enters sleep.
1), MMPC prevents the PV cell input voltage from collapsing below its programmed threshold. Peak current limits are automatically adjusted with proprietary techniques to maintain operation at levels that maximize power extraction from the PV cell. The MPPC circuit dynamically regulates the average inductor current to prevent the input voltage from dropping below the MPPC threshold. When VIN is greater than the MPPC voltage, inductor current increases until VIN is pulled down to the MPPC set point. If VIN is less than the MPPC voltage, the inductor current is reduced until VIN rises to the MPPC set point. For more information, see the sidebar “Maximum Power Point Control For A PV Cell.” In PV cell applications, a diode can be used to set the MPPC threshold so that it tracks the cell voltage over temperature. If the selected diode forward voltage is too low, a resistor in series with the diode can adjust the dc set point to better match the maximum power point of the PV cell.
If the diode is located far from the converter inputs, a capacitor may be required to filter noise that may couple onto the MPPC pin. This method can be extended to stacked cell sources through use of multiple series connected diodes. Lowering peak inductor current to 100mA at light load optimizes efficiency by reducing conduction losses. As the load increases, the peak inductor current automatically increases to a maximum of 400mA. This function is overridden by the MPPC and only occurs when the PV cell delivers more power than the load requires. PGOOD indicates that power is good at the beginning of the first sleep event after the output voltage has risen above 90% of its regulation value. PGOOD remains asserted until VOUT drops below 90% of its regulation value at which point PGOOD goes low. To minimize output capacitor discharge in such cases, the LTC3105 incorporates undervoltage lockout (UVLO) that forces the converter into the shutdown mode if the input voltage falls below 90mV (typical).
In shutdown, the switch connecting AUX and VOUT is enabled and the LDO is placed into reverse-blocking mode and the current into VOUT is reduced to 4µA (typical). To minimize discharging of the output, the IC limits reverse current through the LDO to 1µA in shutdown. In applications where the input voltage is very low, a larger value inductor can provide higher efficiency and a lower start-up voltage.
If the inductor dc resistance is too high, it will reduce efficiency and increase the minimum operating voltage. For high impedance PV cells, the input capacitor should be large enough to allow the converter to complete start-up mode using the energy stored in the input capacitor.
When using bulk input capacitors that have high ESR, a small valued parallel ceramic capacitor should be placed between VIN and GND as close to the converter pins as possible. When using output bulk storage devices with high ESR, a low value ceramic capacitor should be placed in parallel and located as close as possible to the converter pins.
The voltage at which PV cell produces maximum power depends on solar radiation, ambient temperature and PV cell temperature. Typical PV cells produce power with maximum power voltage of around 17 V when measured at a cell temperature of 25°C, it can drop to around 15 V on a very hot day and it can also rise to 18 V on a very cold day.



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