Challenges of Low Power Applications

Designing for ultra-low-power electronics requires a trading-off between higher performance against longer battery life. Although battery capacities have improved substantially, the fundamental challenge remains the same as that of achieving higher performance for longer periods.

Reducing the power consumption and managing battery life depends primarily on minimizing the quiescent current of a circuit. This is best explained with the help of a sensor node in the Internet-of-Things. For instance, a low-power IoT application may have a battery-powered MCU controlling the door lock via a Wi-Fi connection or Bluetooth.

As most of these types of systems spend a major part of their operating time in standby mode, the quiescent current consumption in standby or sleep mode is the limiting factor when considering battery life. Careful optimization of power-management blocks of low quiescent current can lead to extending the battery life from a low of two years to a high of five or more years.

The most important bottleneck is in achieving low no-load quiescent current for low-power systems with the duty-cycle operation, as this enables longer battery life. However, designers must tradeoff between output power range, die-package area, and transient noise performance. One must realize that reducing quiescent current by decades without sacrificing performance or area can only come about through reexamining both circuit techniques and silicon technologies.

Standby quiescent current has been a concern. Historically, most solutions limited themselves to a narrow set of low-power systems. However, there have been recent breakthroughs in a quiescent current reduction in power-management building blocks. Now, LDOs or low-dropout regulators and supervisors, power switches, and DC/DC converters are using these blocks for end equipment. These include personal wearables, automotive sensors, and industrial meter applications.

For instance, the quiescent current in 5V LDOs has approximately come down by 90% every three years over the past decade. Not only has the quiescent current reduced, but there have been circuit improvements and optimization of process technologies that have led to the reduction of die area while improving the transient-noise performance.

So, what constitutes quiescent current? Basically, this is the amount of current drawn when the circuit is in an enabled condition but not supporting an external load, and not switching. This is different from the shutdown current, which the device draws from the power supply when it is in a disabled condition.

Power regulators are mostly always-on functions, and their quiescent current contributes to the overall system quiescent current. Within the power regulator, all voltage references, error amplifiers, output voltage dividers, and protection circuits contribute to the overall operating currents.

Therefore, designers determine the quiescent current that a device draws from a battery or power source by taking into account the always-on functions and leakage sources from inductors, capacitors, and resistors.

On the other hand, switching converters are different. Most switching converters include a power-saving mode. This enables a longer period for non-switching times, resulting in a reduction of the average quiescent current. But most low-quiescent current devices have internal parasitic capacitors. These cause a longer response time as they must change to the new operating point.

LIDAR with MEMS

A solid-state Lidar chip works by emitting laser light from an optical antenna. A tiny switch turns the antenna on and off. The light reflects off the sample and the same antenna captures it. For 3D imaging, the Lidar chip has an array of such antennae. The switches sequentially turn them on in the array.

An array of MEMS switches for high-resolution solid-state Lidar can reduce its cost significantly. This allows the solid-state Lidar to match other inexpensive chip-based radar and camera systems. This removes the major barrier to the adoption of Lidar for autonomous vehicles.

At present, autonomous highway driving and collision avoidance systems use inexpensive chip-based radar and cameras as their mainstream building blocks. At the same time, Lidar navigation systems, being mechanical devices and unwieldy, are also expensive, costing thousands of dollars.

However, researchers at the University of California, Berkeley, are working on a new type of high-resolution Lidar chip and this may be the game-changer. The new Lidar uses an FPSA or Focal Plane Switch Array. This is a matrix of micron-scale antennas made of semiconductors. Just like the sensors in digital cameras do, these antennas also gather light. While smartphone cameras have impressive resolutions of millions of pixels, FPSA on the new Lidar has a resolution of only 16,384 pixels. However, this is substantially larger than the 512 pixels that the current FPSA has.

Another advantage of the new FPSA is its design is scalable. Using the same CMOS or Complementary Metal-Oxide Semiconductor technology that produces computer processors, it is possible to reach megapixel sizes easily. According to the researchers, this can lead to a new generation of 3D sensors that are not only immensely powerful but also low-cost. Such powerful 3D sensors will be of great use in smartphones, robots, drones, and autonomous cars.

Surprisingly, the new Lidar system works the same way as mechanical Lidar systems do. Mechanical Lidars also use lasers for visualizing objects situated several hundreds of yards away, even when they are in the dark. They also generate high-resolution 3D maps for the artificial intelligence in a vehicle for distinguishing between obstacles like pedestrians, bicycles, and other vehicles. But for over a decade, researchers have tried to put these capabilities on a chip, without success, up until now.

The idea is to illuminate a large area. However, the larger the area illuminated, the weaker is the light intensity. This does not allow reaching a reasonable distance. Therefore, researchers had to make a trade-off for maintaining the light intensity. They had to reduce the area that their laser light was illuminating.

The new Lidar has an FPSA matrix consisting of tiny optical transmitters. Each transmitter has a MEMS switch that can rapidly turn on and off. This allows time for the waveguides to move from one position to another while allowing channeling the entire laser power through a single antenna at any time.

Routing light in communications networks commonly uses MEMS switches. The researchers have used this technology for the first time for Lidar. Compared to the thermo-optic switches that the mechanical Lidar uses, the MEMs switches have the advantage of being much smaller, consuming far less power, operating faster, and performing with significantly lower light losses.

Encoders for Autonomous Mobile Robots

Whether it is AMR or autonomous mobile robots, AGC or automated guided carts, AGV or automated guided vehicles, various types of robots or robotics are increasingly important to the industry. They use these robots to move parts and materials from one place to another in every environment. For instance, goods move from manufacturing to warehouse, and thence to grocery stores to face customers.

It is important that these automated machines work correctly because precision is a vital requirement. This requires reliable motion feedback to the controllers. This is where encoders come in. For instance, autonomous motion applications requiring motion feedback are useful in steering assembly, drive motors, lift controls, and more.

The industry uses several automated carts and vehicles. They use them for lifting products and materials onto and from shelves and floors in warehouses and other storage areas. To do that reliably and repeatedly, these machines require accurate and precise motion feedback. This ensures that materials and products reach where they need to go, without incurring damages.

The Encoder Product Company offers to draw wire solutions, and encoders with rack-and-pinion gears provide reliable motion feedback. This ensures all lifts stop at the right locations, thereby moving materials and products safely to their destinations. Their motion feedback options for lift control involve Model LCX, for high performance with absolute feedback option, and Model TR2, a rack-and-pinion gear as an all-in-one unit.

The Model LCX135 is one of a draw wire series, providing an excellent solution for the control of lifts. Internally, incremental and absolute encoders provide excellent lift control feedback using the CANopen communication protocol.

Automated carts and vehicles require drive motor feedback. As they move around facilities like warehouses, the controller in these vehicles needs reliable motion feedback to ensure the motors are in the proper transit areas/corridors designated for them. The motion feedback also ensures they stop and start accurately.

Motion feedback devices from the Encoder Product Company provide this reliable, repeatable motion feedback. Their Model 15T/H is a compact and high-performance encoder. It is available in the blind-hollow bore or thru-bore designs. The Model 260 is a more economical and compact encoder with a large thru-bore design. The next model 25T/H is a high-performance 2.5” encoder. While Models 25T and 260 are incremental encoders, absolute encoders are also available, and they use the same CANopen communication protocol.

To ensure the correct drive path ad steering angle, the steering assembly also needs to provide precision feedback. Absolute encoders provide the best way to ensure proper motion feedback for these steering assemblies. This is because with absolute encoders it is possible to ensure smart positioning while providing the exact location while in a 360-degree rotation.

The Encoder Product Company offers several absolute encoders. Among them is the Model A36HB, a compact absolute encoder with a 36 mm blind hollow bore. Another is the Model A58HB, an absolute encoder with a 58 mm blind hollow bore.

Where safety is considered paramount, the Encoder Product Company offers redundant encoders. These are simple solutions and economical also. Using redundant encoders allows the application to rely on different technologies, ensuring at least one encoder will continue to function even when the other has failed.

Passive and Active Thermal Management

Keeping electronics cool is an important goal for designers, and they have a wide variety of options with active and passive thermal management. With power densities continuing to increase, and microprocessors drawing more power for meeting the demands of computational and functional requirements made by high-powered applications, thermal management is, even more, a requirement.

Today, densely populated circuit boards use high-power components to create systems that generate more heat than ever before. Therefore, designers face an upward challenge in implementing effective thermal design and management, as heat is the major cause of electronic failure.

The operational life and functionality of components can be compromised severely when the application exposes them to high localized temperatures, or when they operate at excessive temperatures. Prolonged operation in these extreme conditions can also lead to degradation of the components and ultimately, failure.

Designers ensure reliability and proper performance by arranging to transport the excess heat away from system hot spots and critical components. By dissipating this heat to the ambient environment, they manage to keep the system temperature within acceptable limits. Thermodynamics offers three basic methods of heat transfer that designers use to their advantage. They derive the thermal solutions from the basic principles of conduction, convection, and radiation.

Conduction allows heat to flow from an area of higher temperature to one with a lower temperature, provided both are within a single medium, which can be a solid, liquid, or gas. The process of conduction attempts to equalize thermal differences. The process also transfers heat between media in direct physical contact, such as between two touching solids.

Convection is the process of transfer of heat between a solid body and a fluid, which can be liquid or gas. The bulk motion of the fluid helps in the heat transfer. During the natural convection process, cold ambient air assimilates heat from any heated surface nearby. The air becomes warmer and, therefore, less dense, causing it to rise and creating low pressure. Cooler air from the surrounding areas rushes in to balance the low pressure created by the rising warm air, which, in turn, rises when it warms up. This creates a natural cycle of airflow, removing the heat.

In the process of radiation, a hot body radiates thermal energy as electromagnetic waves. The surface condition of the radiating surface and its temperature determines the amount of emission. Likewise, a cold body can absorb electromagnetic waves, and the amount it can absorb depends on its surface condition, its temperature, and the temperature of the surrounding environment.

All the above are examples of passive thermal management. These are commonly in use as they are easy to implement and are the least expensive. In some situations, however, passive thermal management is not adequate for removing excess heat. These situations call for active thermal management, such as using a fan to force an air-flow movement over the heated surface. Controlling the airflow may require a change in the fan size and its configuration. Optimization of the flow path may require proper placement of the fan and its orientation.

What is a Thermal Switch?

Future spacecraft carrying humans require thermal management systems with high turn-down capabilities. In widely varying thermal environments, thermal switches can dissipate a wide range of heat loads. Thermal switches are electromechanical on/off switches, and they are thermally actuated. In contrast with thermal fuses, thermal switches are reusable. They are well suited for protection against common temporary thermal situations, that the user can correct.

A temperature differential activates a thermal switch. When activated, the state of the switch changes over from either normally open to closed or normally closed to open. The movement of the contacts can generate a faint audible noise, as they interrupt the power to an electrical circuit.

Applications of thermal switches include preventing damage from over-heating of electrical circuits. However, these switches may also be useful as temperature control devices, such as in water heaters. The switches are helpful in preventing overheating in various consumer, industrial, and commercial products. In practice, they control the power to circuitry in electric motors, power supplies, lighting fixtures, transformers, ballasts, and battery packs. When controlling temperature, these switches are useful in electronic cooling fans, heat pumps, low voltage relays, or gas furnaces operated by a solenoid valve.

Several types of thermal switches are available. These include bi-metallic disc or snap action, mercury switches, thermal reed switches, rod and tube switches, vapor-tension switches, and gas-activated switches.

The snap action or bi-metallic disc switches operate based on the phenomenon of thermal expansion. The switch has two dissimilar metals that expand at different rates. As the temperature reaches the threshold, the snap action of the discs forces the switch to activate.

In mercury switches, the contacts are sealed within a glass envelope containing a small amount of mercury. At temperatures above 40 ℃, mercury is always in a liquid state. As mercury is also a good conductor, it can make or break the contacts based on the angle of inclination. Typically mounted on a metal coil, the switch activates with thermal expansion that causes the coil to tilt.

Thermal reed switches have a pair of contacts on ferrous metal reeds inside a hermetically sealed glass tube. As the metal reeds are ferrous, a magnetic field can activate them. The switch can have either normally open or normally closed contacts, kept in that state by a ferromagnetic material surrounding the glass tube. As temperature rises and reaches the curie point of the ferromagnetic material, it loses its magnetic strength, and this alters the state of the contacts.

Rod and tube thermal switches are made of an outer tube surrounding an internal rod, both made of metals with dissimilar coefficients of thermal expansion. When the temperature rises, the rod expands faster than the tube can, and induces a plunger-style contact. Rod and tube thermal switches have rapid response times and can operate at high temperatures.

Vapor tension or gas-activated thermal switches use a sensing bulb with a gas or vapor inside. As temperature rises, the thermal expansion of the vapor or gas leads to a proportional pressure increase on a piston assembly or a diaphragm, actuating an electrical switching system.

Batteries without Mass

Electric vehicles use various types of batteries to operate. But all of them have one thing in common—the weight of the batteries. Depending on the size of the vehicle, the battery weight is a significant part of the total weight of the vehicle. As a vehicle must carry its batteries along with it, it is unable to fully utilize its total capacity. Engineers and scientists are researching various ways of reducing the battery weight while enhancing its energy density.

Some scientists are thinking in more innovative ways. For instance, scientists in Sweden claim to have developed a structural battery. The advantage of such a battery is it is purportedly stored without mass, as its weight is actually a part of the load-bearing structure. With an energy density of 24 Wh/kg, the design of the battery allows solar-powered vehicles to integrate it easily.

At the Chalmers University of Technology in Sweden, scientists claim to have developed a structural battery. The construction primarily uses carbon fiber, and apart from the structure of the battery, the carbon fiber also acts as a load-bearing material, conductor, and electrode.

Structural batteries use materials with properties of electrochemical energy storage. The primary aim of such devices is to reduce the weight of an object, as the manufacturer can embed the battery to be a part of the structure of the object, such as a drone or an electric vehicle.

According to the scientists, they had started research and developing their massless batteries in 2007. Their main challenge had been to build devices that had good mechanical and electrical properties. They settled on carbon fibers for their battery, as it has the required strength and stiffness to allow integration into structures of electric vehicles. In addition, carbon fibers also exhibit good storage properties.

The scientists claim their batteries may also be applicable to the roof of light city vehicles such as rickshaws. The roof of these vehicles may have solar cells.

The batteries have a structural battery electrolyte matrix material, housing a negative electrode made of carbon fiber, and a positive electrode supported with aluminum film. A glass fiber separator keeps the two electrodes apart.

Apart from reinforcing the material, the carbon fiber also helps to conduct electrons while acting as a host for Lithium. In the same way, the positive electrode foil, apart from providing electrical functionality, also provides mechanical support.

The structural battery electrolyte favors the transport of Lithium ions while transferring mechanical load between the fibers of the device, its particles, and plies. The scientists demonstrated a battery with an elastic modulus of 25 Gpascals and a tensile strength that exceeded 300 Mpascals. While the elastic modulus demonstrates the resistance of the material to elastic deformation, the tensile strength demonstrates the maximum load that the material can support without damage.

With an energy density of 24 Wh/kg, the battery has about twenty percent capacity relative to presently available lithium batteries. However, as the battery reduces the weight of the vehicle significantly, the electric vehicle requires much less energy. Additionally, the lower energy density results in increased safety for the vehicle and its passengers.

Advancements in Hybrid Thermal Management

Over the past few decades, the fastest-growing electronic industries have been power and energy. These include fuel cell and battery technologies, and power inversion, conversion, and rectification.

With form factors getting smaller, power electronic systems are becoming increasingly complex, while, at the same time, performing at higher power ranges. That makes heat generated within the system the greatest limiting factor to its functioning. To dissipate the amount of power the system generates, it is necessary for the designer to optimize and enlarge air cooling systems to remove the heat effectively. In some cases, size is the limiting factor for systems using forced convection. Where the weight or size of the air-cooled solution becomes impractical, engineers prefer to use liquid cooling as an alternative method.

However, it is not easy to switch quickly from an air-cooled system to a liquid one. Designers must consider several factors and possibilities for improving thermal management for handling higher heat loads. Although the market is trending towards full liquid cooling as the industry standard for cooling power electronic systems in the future, engineers can also consider various hybrid solutions. That helps to apply the benefits of hybrid systems as the system evolves or upgrades.

Engineers use liquid cooling systems, making them complementary to existing air-cooled solutions. That allows them to expand it gradually to replace the air-cooled system. They do this with a focus on the electronic systems that benefit from liquid cooling. For this, they employ fluid couplings, dependable pump systems, and compact heat exchangers. The system transfers heat from airflow to liquid flow that transports it elsewhere to manage it. If this is not possible, engineers have the option of fully replacing the air-cooled system with a liquid-cooled one, thereby enabling higher power outputs while optimizing the thermal performance.

Engineers must consider numerous key determining factors for improving the performance of any power electronic devices and facilities while switching to liquid cooling. They must consider the thermal performance requirements in addition to the size and weight requirements. They must also look into further optimizing the present air cooling system and whether it will still remain a viable thermal option. Furthermore, they must also look into any limitations on the availability of the liquid cooling system. As cost is always a huge factor in any project, the engineer must also look into the return on efficiency and performance when investing in liquid cooling. Also, they must look into the downtime necessary for the conversion and the easiest way of implementing the changeover.

Both forced, and natural thermal management has limitations. The total surface area necessary to dissipate heat limits natural thermal management systems, necessitating heavy and large, but impractical solutions.

On the other hand, pressure drop limits solutions using forced convection. Heat sinks require large surface areas in viable volumes. This creates high amounts of air resistance. But this also hinders the amount of airflow, thereby limiting the heat transfer from a fan. This, in turn, requires larger or more fans, and this increases the amount of noise in the system.

Two-Phase Thermal Switches

Spacecrafts frequently make use of a wide range of variable conductance devices for thermal management. These devices, also known as thermal switches, help to maintain the temperature of heat sources that operate under varying thermal environments and thermal loads within a spacecraft. Many such applications are already operating in Lunar and Mars landers and rovers, and in satellites. Being highly reliable, scientists may be using thermal switches in the future for human spacecraft transiting through space.

Two-phase thermal switches are low-mass, and they meet the above requirements very well. The temperature of the heat source passively triggers the switching mechanism. The operation of thermal switches is similar to the functioning of a heat pipe with flexible walls.

A two-phase thermal switch consists of a hermetic enclosure housing sealed metallic bellows. The bellows have one of its ends fixed to the enclosure, which, in turn, is in contact with the heat source. Within the bellows, there is a wick structure along with a small amount of saturated working fluid.

The heat from the source enters the enclosure and the bellows, heating the working fluid. The heat vaporizes the fluid, increasing the saturated vapor pressure inside the bellows. The increasing pressure causes the bellows to expand until it makes contact with the other end of the enclosure, which is in contact with a heat sink.

The temperature of the saturated vapor that causes the pressure at which the bellows makes contact with the heat sink end of the enclosure, is the setpoint temperature of the two-phase thermal switch. The design of the two-phase thermal switch determines its setpoint temperature. One of the components deciding the set point temperature is the gas pressure within the enclosure, as it opposes the expansion of the bellows. Users can remotely adjust the set point temperature of a two-phase thermal switch by changing this counter pressure. The switch maintains the heat source at its set-point temperature as the heat sink conducts heat away from the enclosure.

As the name suggests, a two-phase thermal switch operates in two phases. The first phase is similar to a conventional thermal switch. The device switches from a low conductance state to a high conductance state and back as the heat source supplies heat or removes it.

The second phase of the switch comes into effect during its high conductance state. In this condition, the device also operates as a variable conductance device for maintaining the heat source at its set-point temperature. The design of the device allows it to maintain the temperature of the heat source at the set point while the heat sink temperature varies wildly. The variable conductance is a result of the dynamic motion of the bellows as it oscillates and periodically connects with the heat sink.

Two-phase thermal switches are capable of dissipating a wide range of heat loads during widely ranging thermal environments. Their low mass, simple design, low cost, and higher on to off conductance ratios are positive factors in spacecraft applications. At high temperatures of the heat source, the bellows may not disconnect from the sink, essentially acting as a heat pipe.

Selecting Industrial Enclosures

Industrial environments can be harsh, possessing the potential for causing expensive damage to equipment accompanying any investments in technology. Therefore, it is important to select the right industrial enclosures to protect, cool, and power systems for applications. Several key questions can come up when considering industrial enclosures and their selection.

Modern businesses prefer modular enclosures, as they provide flexibility, allowing evolution with the changing demands of business lifecycles. Compared to traditional unibody enclosures, modular enclosures may provide up to 30% more mounting space. Additionally, modular enclosures are typically lighter than welded units but capable of holding an equivalent weight of the material.

Modular enclosures may have additional advantages over their traditional counterparts. For instance, most modular enclosures offer greater surface area, thereby increasing the capacity for adding more accessories. The additional accessories may include fold-up keyboard shelves, LED lighting, and busbar power.

With doors capable of opening from either the right or the left side, modular enclosures offer swapping of lock systems without requiring tools. Reversible doors offer easy addition of IoT-enabled access controls or biometric controls. One can also send alerts by email and/or phone if the door is open, thereby improving remote security monitoring.

As it is possible to allow the frame to hold components also, the design does not limit itself to mounting the panel alone. Therefore, the user can fully utilize the interior of the enclosure. In other words, users can shrink the footprint of the enclosure, while still maintaining the operational capabilities.

When selecting the material for an industrial enclosure, it is preferable to look for carbon steel or stainless steel. Painted carbon steel is most suitable for indoor enclosures and is the most cost-effective among all metallic enclosures. It is easy to get a paint finish that is scratch resistant. Carbon steel with a painted surface has limited resistance to acids, alkalis, and solvents.

However, for the greatest protection from corrosion, rust, high-pressure washes, chemicals, and various harsh weather conditions, stainless steel enclosures offer the best solutions. Industries dealing with food and beverages, pharmaceutical, mining, wastewater, and oil and gas, use stainless steel enclosures extensively. Of the two main types of stainless steel available for enclosures, type 316 and 304, type 316 offers the highest resistance to corrosion, both for indoor and outdoor use.

Selecting modular enclosures with frame options that accommodate multiple door options offers more flexibility. For instance, it is easy to configure several small partial doors when considering a solution for custom motor control centers.

Consider foamed-in-place gaskets for modular enclosures, as it is possible to pour the gasket in a continuous manner around the perimeter of the doors and sidewall, thereby ensuring no gaps exist. Not only does this provide a better seal and memory retention, it also increases protection from corrosive materials and atmospheric conditions.

It is also possible to use an external skin with modular enclosures. This feature allows removing the sidewall, doors, and other parts, thereby offering greater access to internal components. It also allows more accurate modifications and cutouts on the enclosure. Stainless steel panels with an L-fold around the perimeter offer greater stiffness.

MEMS Technology for CO2 Sensing

Most technologies for detecting CO2 are based on photo-detection, where smoke particles reflect light that photo-sensors can detect. However, MEMS technology now offers a more sensitive technology for detecting CO2. Using their knowledge in sensors and MEMS technology, Infineon has now introduced a disruptive gas sensor for sensing CO2 gas.

Coming in a minuscule form factor, the XENSIV PAS CO2 from Infineon is a real CO2 sensor. Infineon has based it on the principle of photoacoustic spectroscopy or PAS. Infineon uses a MEMS microphone, which they have optimized for low-frequency operation. The sensor has a cavity that can detect pressure changes generated by CO2. An integrated microcontroller in the sensor then delivers the CO2 concentration in the form of a direct ppm readout. As the absorption chamber of the sensor is acoustically isolated from external noise, the sensor guarantees highly accurate readings of CO2.

XENSIV PAS CO2 has impressive features. Its operating range extends from 0 ppm to 10,000 ppm, with a linear response giving an accuracy of 30 ppm +3% of reading between 400 ppm and 5,000 ppm. The operating temperature range of the sensor is 0-50 °C at a relative humidity (non-condensing) of 0-85%.

The sensor requires two supply voltages, 12VDC for the emitter and 3.3VDC for its other components, and its average power consumption is typically 30 mW when operating at 1 measurement per minute. With a package dimension of 13.8 x 14 x 7.5 mm, the sensor offers three interface standards—I2C, UART, and PWM.

XENSIV PAS CO2 has several potential applications. On account of its high accuracy, SMD capabilities, and compact size, the sensor is ideally suitable for indoor air quality monitoring with numerous potential applications. For instance, the sensor is highly suitable for home appliances for air conditioners and air purifiers. It is also suitable for smart home IoT devices like smart lighting, indoor air quality monitors, personal assistants, baby monitors, speakers, and thermostats. Apart from use in in-cabin air quality monitoring in aircraft, the sensor is eminently suitable for city management and CO2 emission control in advertising billboards, bus stations, and outdoor lighting.

While measuring the CO2 concentration, the sensor operates in one of two modes—active state and inactive state. In the active state, the integrated CPU is in an operating state and performs tasks like running a measurement sequence or serving an interrupt. However, when the sensor has no specific task to perform, the CPU enters an inactive state. The device may enter an inactive state from an active state at the end of a measuring sequence.

During an inactive state, the CPU controlling the device can enter a sleep mode to optimize the consumption of power. Several events can wake up the CPU from its inactive state—a falling edge on the PWM pin, reception of a message on the serial communication interface, or the internal generation of a measurement request when the device is in continuous measurement mode.

It is possible to program the sensor module via its serial communication interface to operate in one of three modes—idle mode, Continuous mode, and Single-Shot mode.