|L-Band||The group of radio frequencies extending from 390MHz to 1550MHz. The GPS carrier frequencies (1227.6MHz and 1575.42MHz) are in the L-band.|
|LAN||Local Area Network: A computer network, usually within one building, that connects computers, file and mail servers, storage, peripherals, and other devices in a way that permits data interchange and sharing of resources. Ethernet and WiFi (802.11) are common examples.|
|Large-scale integration||See LSI|
|Laser Diode Driver||See Laser Driver|
|Laser Driver||An IC that supplies modulated current to a laser diode in response to an input serial-data stream.|
|LC circuit||See Resonant Circuit|
|LCC||1. Leadless Ceramic Chip Carrier or Leadless Chip Carrier: An IC package, usually ceramic, that has no leads (pins). It instead uses metal pads at its outer edge to make contact with the printed circuit board. Example: Maxim 20-pin LCC diagram (PDF)
2. Leaded Chip Carrier, also called PLCC or Plastic Leaded Chip Carrier: A square surface mount chip package in plastic with leads (pins) on all four sides. Example: Maxim 20-pin PLCC diagram (PDF)
Low Drop Out: A linear voltage regulator that will operate even when the input voltage barely exceeds the desired output voltage.
Learn More: Linear Regulators (LDOs)
|LDO Regulator Low Dropout Regulator||See LDO|
|Leaded Chip Carrier||See LCC|
|Leadless Chip Carrier||See LCC|
Leakage inductance in a transformer is an inductive component that results from the imperfect magnetic linking of one winding to another.
In an ideal transformer, 100% of the energy is magnetically coupled from the primary to the secondary windings. Imperfect coupling reduces the signal induced in the secondary windings. The electrical equivalent is some self-inductance in series with the primary windings that are properly coupled. This series inductance is the "leakage inductance."
|LED||Light-Emitting Diode: A semiconductor device that emits light (usually visible or infrared) when forward-biased.
The application note, "Driving LEDs in Battery-Operated Applications: Controlling Brightness Power Efficiently" has a good explanation of how LEDs work, especially with regard to current vs. LED brightness and schemes for matching brightness when driving multiple LEDs.
A level translator is a device which translates a logic signal from one type to another, for example, ECL to TTL.
Learn More: Level Translators
A linear Feedback Shift Register is a shift register in which some of its outputs are connected to the input through some logic gates (typically, an XOR).
A wide variety of bit patterns can be generated inexpensively, including pseudo-random sequences. Can be used as a noise generator.
|LGHL||Low gain, high linearity|
|Li||See Lithium batteries|
|Li+||See Lithium-ion batteries|
|Li-Ion||See Lithium-ion batteries|
|Li-po||See Lithium-ion batteries|
|Li-poly||See Lithium-ion batteries|
LiDAR (light detection and ranging) is a remote sensing method that uses laser beams to create a 3D scan of the surrounding area. LiDAR is an important means of proximity sensing in autonomous vehicles.
What is LiDAR and how does it work?
LiDAR works by emitting pulses of laser light and measuring the return time between the emitted signal and the signal that is reflected after bouncing off of a nearby object. Since LiDAR uses light signals, the distance to the object is easily calculated by multiplying the time of flight by the speed of light. The use of light also makes for very quick return times.
The distance map in (B) shows the objects detected in (A) by a LiDAR laser/receiver system. The closest object (in red) has the shortest time of flight, while the farthest (in green) has the longest.
By continually emitting these short laser bursts, and in multiple directions, the system can create a distance map of all of the surrounding objects that updates instantly and continuously.
Illustration of autonomous vehicles emitting LiDAR signals in multiple directions to detect objects on the road.
How does a LiDAR laser/receiver system work?
The block diagram above shows a typical operating circuit. The laser driver initiates the light pulse towards the object, and the returned signal reflects into the photodiode D1 which converts the light to current. The transimpedance amplifier TIA1 converts the current to voltage and amplifies the signal to then be sent to the comparator COMP1, which converts the analog signal to a digital one. The D2/TIA2/COMP2 system works similarly to record the initial signal, and all of this information is processed and stored by the MCU.
LiDAR vs. radar
LiDAR and radar are similar in that they both measure time of flight to determine distance from an object, and the difference is what type of signal they use. Where LiDAR is Light Detection and Ranging, radar is Radio Detection and Ranging, and these are the types of waves that each system emits. Light waves are in the nm to μm wavelength range, where radio waves are in the cm to km wavelength range.
LiDAR’s smaller wavelengths make it able to create more precise and accurate distance maps, detecting smaller objects and greater detail. Radar’s longer wavelength range makes it less sensitive to changes in the medium through which it travels (such as poor weather). Because of these differences, the two are often used together (sometimes with cameras) to form vision and driving capabilities that exceed those of humans.
Light sensors are a type of photodetector (also called photosensors) that detect light. Different types of light sensors can be used to measure illuminance, respond to changes in the amount of light received, or convert light to electricity.
What are the different types of light sensors?
Common types of light sensors are photodiodes, photoresistors, phototransistors, and photovoltaic light sensors. These components can be used in applications such as light sensing in mobile devices, automatic outdoor lighting, proximity sensors, and renewable energy.
Photodiodes convert light into an electrical current. They are p-n junction devices that are similar to normal diodes. A p-n junction device consists of a p-type and an n-type semiconducting material. The “p” stands for “positive” due to the material’s excess of electron holes, and the “n” stands for “negative” due to an excess of electrons. This means that current can only flow in one direction through the boundary. In a photodiode, these electron hole pairs are formed when the energy from the incident light is absorbed by the device. Also see the related term avalanche photodiode.
Photoresistors (also known as light-dependent resistors or LDRs) are passive devices that decrease resistance in proportion to the amount of light received. Light forming electron hole pairs increases conductivity and therefore decreases resistivity.
Phototransistors switch or amplify signals similarly to regular transistors, with the current applied to the terminals being created from exposure to light.
Photovoltaic (or solar cells) convert light into electricity in a process known as energy harvesting. Voltage and electric current are generated by way of the photovoltaic effect exhibited by the cell's semiconducting components.
How do light sensors work?
Light sensors work by the photoelectric effect. Light can behave as a particle, referred to as a photon. When a photon hits the metal surface of the light sensor, the energy of the light is absorbed by the electrons, increasing their kinetic energy and allowing them to be emitted from the material. This movement of electrons, and therefore charge, is electrical current.
The photovoltaic effect is similar to the photoelectric effect in that the light is absorbed by electrons, causing them to be in a higher-energy state. In the photoelectric effect, the electrons are ejected from the material completely. In the photovoltaic effect, the electrons are excited from the valence band into the conduction band, but remain within the same material.
|Light-Emitting Diode||See LED|
|LIN||Local Interconnect Network (LIN): Defined by the LIN-BUS consortium, a LIN is a low data-rate, single-wire communications system, used in automotive and heavy vehicle applications.|
|Line Regulation||The ability of a power-supply voltage regulator to maintain its output voltage despite variations in its input voltage.|
|Linear||1. Having the property that the output is proportional to the input. E.g.:
VOUT = k*VIN
where k is a constant.
2. Analog; as in a "linear" circuit (as opposed to digital).
|Linear Amplifier||See Class A|
|Linear Fan Control||See Fan Controller - Linear|
|Linear Feedback Shift Register||See LFSR|
|Linear Mode||Uses a linear-pass element (BJT or FET) to control/regulate the charging voltage/current.|
A voltage regulator that is placed between a supply and the load and provides a constant voltage by varying its effective resistance.
|Linear Taper||See Taper|
|Lion||See Lithium-ion batteries|
|Lipo||See Lithium-ion batteries|
|Lithium||See Lithium batteries|
|Lithium batteries||Lithium batteries for low-power, high-reliability, long-life applications such as non-volatile memory and timekeeping (typically in coin-shaped cells) use a variety of lithium-based chemistries (as differentiated from lithium-ion).
Maxim NV SRAM and timekeeping products use mostly BR chemistry (poly-carbonmonofluoride) primary (non-rechargeable) lithium coin cells. We use CR chemistry (manganese dioxide) primary lithium coin cells in microcontroller and touch products. Some new products use "manganese lithium" (ML) chemistry, which is chemically close to the CR, but is a secondary (rechargeable) lithium coin cell.
|Lithium Ion||See Lithium-ion batteries|
|Lithium-Ion||See Lithium-ion batteries|
|Lithium-ion batteries||Lithium and lithium-ion: A number of battery chemistries are based on the element lithium, a highly-reactive metallic element. Lithium-based batteries are common in two applications: Power for portable equipment such as cell phones, laptops, and MP3 players; and low-power, long-life applications such as powering memory elements and clocks.
Lithium-ion (Li+, Li-Ion, Lion) cells are generally used as power sources for portable equipment. They are usually rechargeable. Lithium-ion and nickel-metal-hydride (NiMH) have displaced nickel-cadmium (NiCd or nicad) as the dominant rechargeable chemistry for portable applications. Maxim makes a wide range of battery management products for all these families, including chargers, fuel gauges, and smart battery components.
Lithium batteries are typically coin-shaped and are used to power items such as Maxim's non-volatile static RAM (NV SRAM) and timekeeping circuits (such as real-time clocks).
|Lithium-ion polymer||See Lithium-ion batteries|
|Lm/W||Lumen(s) per watt|
|LMDS||Local Multipoint Distribution Service: A broadband radio service, located in the 28GHz and 31GHz bands, designed to provide two-way transmission of voice, high-speed data and video (wireless cable TV). In the U.S., FCC rules prohibit incumbent local exchange carriers and cable-TV companies from offering in-region LMDS.|
|LNA||Low noise amplifier. Typical use: The first stage of a satellite receiver.|
|Load Regulation||Load regulation refers to circuitry that compensates for changes in load. Most commonly: Circuits that keep voltage constant as load varies.|
|Local Interconnect Network||See LIN|
|Local Multipoint Distribution Service||See LMDS|
Local temperature is the temperature measured on the die of the temperature-measuring integrated circuit.
|Local Temperature Sensor||
A local temperature sensor is an element or function of an integrated circuit that measures its own die temperature.
|Log Pot||See Taper|
|Logarithmic Pot||See Taper|
|Logarithmic Potentiometer||See Taper|
|Logarithmic Taper||See Taper|
|LOL||Loss of lock|
|Long Haul||A network that spans distances larger than a local area network (LAN). Because electrical and optical transmissions fade over distance, long-haul networks are difficult and expensive to implement.|
|Long Term Evolution||LTE (Long Term Evolution) is a high-speed mobile communications cellular standard developed by the 3rd Generation Partnership Project (3GPP). LTE is an evolution of GSM/UMTS standards.|
|Long-Haul||See Long Haul|
|LOP||Loss of power|
|LOS||Loss of signal|
|Low Batt. Det.||Low battery detector|
|Low Drop Out||See LDO|
|Low Dropout||See LDO|
|Low Dropout Linear Regulator||See LDO|
|Low Frequency Gain Boost||See Bass Boost|
|Low Line O/P||Low line output|
|Low Noise Amplifier||See LNA|
|Low Voltage Differential Signaling||See LVDS|
|Low Voltage Emitter Coupled Logic||See LVECL|
|Low Voltage Positive Emitter Coupled Logic||See LVPECL|
|Low Voltage Transistor-Transistor Logic||See LVTTL|
A low-pass filter (LPF) is a circuit that only passes signals below its cutoff frequency while attenuating all signals above it. It is the complement of a high-pass filter, which only passes signals above its cutoff frequency and attenuates all signals below it.
What is a low-pass filter used for?
Low-pass filters have applications such as anti-aliasing, reconstruction, and speech processing, and can be used in audio amplifiers, equalizers, and speakers.
Low-pass filters can also be used in conjunction with high-pass filters to form bandpass, band-stop, and notch filters. A bandpass filter passes a range of frequencies while attenuating all frequencies outside of the band. A band-stop filter (also called a band reject filter) does the opposite, attenuating signals within its stopband while passing all frequencies outside of it. Notch filters are a type of band-stop filter that attenuate a very narrow set of frequencies, which can be created from a combination of low-pass and high-pass filters with cutoff frequencies very close to each other.
What is a low-pass filter circuit?
There are many different low-pass filter circuits, which are characterized by their order and amplitude characteristic or the type of polynomial that describes it (Butterworth, Chebyshev, Elliptic, or Bessel):
Butterworth - response that is flat in the passband and an adequate rate of rolloff.
Chebyshev - frequency cutoff is steeper than that of a Butterworth, at the cost of a variation in amplitude known as ripple in the passband.
Elliptic (or Cauer) - compared to the Chebyshev, the stopband cutoff is sharper (without incurring more passband ripple), but transient response is worse.
Bessel - represents a trade-off in the opposite direction from the Butterworth. Transient response is improved, but at the expense of a less steep cutoff in the stopband.
Amplitude and group delay vs. frequency for various filter types normalized to a 1-rad bandwidth.
For more on first and second order filters, as well as Butterworth, Chebyshev, Elliptic, and Bessel filters, see Tutorial 733: A Filter Primer.
|Low-Side||An element connected between the load and ground. Low-side current sensing applications measure current by looking at the voltage drop across a resistor placed between the load and ground.|
|LRC circuit||See Resonant Circuit|
|LSB||Least-significant bit. In a binary number, the LSB is the least weighted bit in the number. Typically, binary numbers are written with the MSB in the left-most position; the LSB is the furthest-right bit.|
|LSI||Large-scale integration (LSI). See VLSI.|
|LTE||See Long Term Evolution|
1. The emitted light, projected per unit area, measured in cd/m2 (candela per square meter). Often incorrectly equated with "brightness".
2. The black and white portion of a video signal, also referred to as the "Y" component. A composite, Y/C, or Y/Pb/Pr video signal combines a luminance signal with color components.
|LVC||Lowest voltage clamp|
|LVDS||Low Voltage Differential Signaling|
|LVECL||Low Voltage Emitter Coupled Logic|
|LVPECL||Low Voltage Positive Emitter Coupled Logic|
|LVS||Layout versus schematic|
|LVTTL||Low Voltage Transistor-Transistor Logic|