Glossary Terms and Definitions Beginning with the Letter D

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D-Pot See Digital Pot
D/A See D/A Converter
D/A Converter Digital-to-analog converter (DAC): A data converter, or DAC, that receives digital data (a stream of numbers) and outputs a voltage or current proportional to the value of the digital data.
DAC See D/A Converter
Daisy Chain A method of propagating signals along a bus in which the devices are connected in series and the signal passed from one device to the next. The daisy chain scheme permits assignment of device priorities based on the electrical position of the device on the bus.
Daisy-Chain See Daisy Chain
Dallastat Trademark for Dallas Semiconductor's line of digital rheostats (digital potentiometers). (Dallas Semiconductor is a subsidiary of Maxim Integrated.)
Damping factor See Q Factor
DAQ See Data Acquisition System
DAS See Data Acquisition System
Data Acquisition System System which acquires data, generally by digitizing analog channels and storing the data in digital form. These systems can be standalone or married to a computer and can acquire multiple channels of data.
Data Converter A/D or D/A converter: An electronic circuit that converts analog signals to digital, or vice-versa.

An analog signal is a continuously varying voltage or current. Its digital counterpart is a stream of digital numbers, each representing the amplitude of the analog signal at a moment in time.

Also see:

Data Management Language See DML
Data Manipulation Language See DML
Data Over Cable Service Interface Specification See DOCSIS
Daylight Running See DRL
Daytime Running Lamp See DRL
Daytime Running Light See DRL
dB Decibels: A method for specifying the ratio of two signals.

dB = 10 times the log of the ratio of the power of the two signals. This is equal to 20 times the ratio of their voltages, if the signals are driving equal impedances.

Decibels are also used to describe a signal level by comparing it to a reference level. The reference is usually defined as 0dB and the dB value of the signal is 10 times the log of the signal's power over that of the reference. A letter is sometimes added to signify the reference. For instance, dBm is relative to 0 dBm = 1mW.

dBA See A-Weighting
dBm A unit that defines a signal level by comparing it to a reference level. The reference level of 0dBm is defined as 1mW. The signal level in dBm is 10 times the log of the signal's power over that of the 0dBm reference.
DBS Direct Broadcast Satellite: A system which broadcasts directly from satellite to the subscriber (end user). Prominent examples in the US are DirecTV and Dish network.
DC Direct current
DC-DC Any of the family of switch-mode voltage regulators, these devices use an inductor to store and transfer energy to the output in discrete packets, resulting in highly efficient power conversion.

See application note 2031, "DC-DC Converter Tutorial" and application note 660, "Regulator topologies for battery-powered systems."
DC-DC Controller A DC-DC converter (switch-mode power supply) in which the power switch (usually a power MOSFET) is external to the IC.
DC-DC Converter See Switching Regulator
DC-DCs See DC-DC
DC/DC See DC-DC
DCE Data communications equipment; interchangeable with DTE
DCM Discontinuous-conduction mode
DCR Direct conversion receiver
DCS Digital Cellular System: Any cellular phone system that uses digital (e.g. TDMA, GSM, CDMA).
DDI Digital data input
DDJ Data-dependent jitter
DDR See DDR Memory
DDR Memory Double Data Rate Synchronous DRAM: A clock is used to read data from a DRAM. DDR memory reads data on both the rising and falling edge of the clock, achieving a faster data rate. Often used in notebook computers because it also consumes less power.
DDR RAM See DDR Memory
DDR-SDRAM See DDR Memory
DDRAM See DDR Memory
DDRD Data direction register D
DDS DDS (direct digital synthesis) is a method for digitally generating analog waveforms, such as sine waves (modulated or not) or arbitrary waveforms.

In the most straightforward realization, a digitized sample of the waveform is stored and the values are clocked out to a D/A converter. Varying the clock rate changes the frequency. Variations in rate and changes to a gain factor can modulate the signal.

Debounce Electrical contacts in mechanical pushbutton switches often make and break contact several times when the button is first pushed. A debouncing circuit removes the resulting ripple signal, and provides a clean transition at its output.

More: Switch Bounce and Other Dirty Little Secrets

Debounced See Debounce
Debouncing See Debounce
Decibel See dB
DECT Digital European cordless telephone
DeepCover DeepCover® is a registered trademark for three families of embedded security products that offer advanced physical security to provide the most secure key storage possible. It includes secure authenticators, security managers, and secure microcontrollers.

DeepCover Secure Microcontrollers integrate advanced physical security to offer the highest level of protection against physical tampering and reverse engineering.

DeepCover Security Managers combine advanced physical security with on-chip, nonimprinting memory to safeguard sensitive data from the slightest physical or environmental tampering.

DeepCover Secure Authenticators implement advanced physical security to provide the ultimate in low-cost IP protection, clone prevention, and peripheral authentication.

DeepCover is a registered trademark of Maxim Integrated Products, Inc.

Delay Line See STC
Delta-Sigma An analog-to-digital converter (ADC) architecture consisting of a 1-bit ADC and filtering circuitry which over-samples the input signal and performs noise-shaping to achieve a high-resolution digital output. The architecture is relatively inexpensive compared to other ADC architectures.

Sometimes called a "sigma-delta" converter.

Delta-Sigma Converter See Delta-Sigma
Dense Wave Division Multiplexing See DWDM
Design for Testability Design For Testability (or Design for Test, or DFT) refers to design techniques that make products easier to test. Examples include the addition of test points, parametric measurement devices, self-test diagnotics, test modes, and scan design.
Deterministic Jitter Reproducible jitter within a given system, under controlled conditions. Also known as bounded jitter.

For more information and illustrations, see:

Development Kit See Evaluation Kit
DFE Decision feedback equalization
DFMEA Design Failure Mode and Effects Analysis (DFMEA) is a method for evaluating a design for robustness against potential failures.
DFT See FFT
DG Differential gain
Differential See Differential Signaling
Differential Non-Linearity See DNL
Differential Nonlinearity See DNL
Differential Remote Output Sensing Uses a Kelvin connection at a remote location to sense the output voltage and better control the voltage at that point.
Differential Signaling Most electrical signals are single-ended, comprised of a single wire and ground. Differential signals use two wires which are the inverse of each other -- when one swings positive, the other swings negative in equal magnitude. The receiving circuit looks only at the difference between the two, ignoring any common-mode voltage. This "push-pull" arrangement reduces the impact of electrical interference because external noise will affect both wires equally and the common-mode rejection will ignore the noise.

Examples: RS-422, RS-485, professional audio signal standards (especially for microphones), the signal lines employed by Ethernet, and the standard twisted-pair analog telephone (POTS) line.

Also see the tutorial, Understanding Common-Mode Signals.

Digipot See Digital Pot
digital amplifier See Class D
Digital Audio Signal Processor See Digital Signal Processor
Digital Cellular System See DCS
Digital Fan Control See Fan Controller - PWM
Digital Log Pot Digital logarithmic potentiometer.
Digital Multimeter See DMM
Digital Pot Digital potentiometer: A solid-state device that emulates a mechanical potentiometer, it is usually controlled via a simple interface.
Digital Potentiometer See Digital Pot
Digital Resistors See Digital Pot
Digital Signal Processor A Digital Signal Processor, or DSP, is a special-purpose digital circuit that acts on digitized signals, such as audio. DSP circuits can replace traditional analog functions, such as filtering and more complex functions that are difficult to accomplish in the analog domain.

A Digital Audio Signal Processor is a DSP for audio applications.

Digital Subscriber Line See DSL
Digital Video Broadcast See DVB
Digital-To-Analog Converter See D/A Converter
DIO Data input/output
Diode A two-terminal device that rectifies signals (passes current in only one direction). Most commonly, a semiconductor consisting of a P-N junction, but dioides can also be realized using vacuum tube, point-contact, metal-semiconductor junction (Schottky), and other technologies.
DIP DIP (Dual Inline Package) is an integrated circuit package with two rows of pins.

PDIP (Plastic Dual Inline Package) is a DIP package with a molded plastic body.

CDIP (Ceramic Dual Inline Package) is a DIP package with a ceramic body.

Direct Broadcast Satellite See DBS
direct digital synthesis See DDS
Direct Memory Access See DMA
Direct-Sequence Spread Spectrum See DSSS
Discrete Fourier Transform See FFT
Distortion In systems that handle electrical signals, distortion is a generally unwanted change in the signal.

Not all signal alterations are considered distortion. For instance, a uniform delay or a linear attenuation or amplification would generally not be considered distortion.

Dithering A common technique to improve digitizing when quantization noise (quantization error/noise) can no longer be treated as random. A small amount of random noise is added to the analog input signal. This added noise causes the digital output to randomly toggle between two adjacent codes, thereby avoiding thresholding effect.
DIU Digital interface unit
Diversity In radio systems, diversity is a method of improving the reliability and capacity by using multiple communication channels to carry each signal.
DJ See Deterministic Jitter
DLC Double-layer capacitor
Dlog Pot See Digital Log Pot
DMA Direct Memory Access: A scheme which reads or writes data directly to memory, bypassing the processor and the processor bus.
DML Data Manipulation Language (or Data Management Language): A language that allows data to be manipulated in a database. In SQL, commands such as DELETE and INSERT are DML commands.
DMM Digital Multimeter: Measuring instrument or VOM (e.g. voltage, resistance, current) with a digital display.
DMMs See DMM
DMP See Dual-Modulus Prescaler
DMR Digital microwave radio
DMT Discrete multitone data transmission
DNL Differential Nonlinearity: A specification that appears in data-converter datasheets. In an ideal D/A converter, incrementing the digital code by 1 changes the output voltage by an amount that does not vary across the device's permitted range. Similarly, in an A/D, the digital value ramps smoothly as the input is linearly swept across its entire range. DNL measures the deviation from the ideal. An ideal converter has the code exactly the same size, and a DNL of 0 (zero).
DOCSIS Data Over Cable Service Interface Specification: A standard for delivering data over cable TV systems, typically for subscriber Internet access services.
Double Data Rate Synchronous DRAM See DDR Memory
Doublers See Voltage Doubler
Down Converter See Down Converters
Down Converters A device which provides frequency conversion to a lower frequency, e.g. in digital broadcast satellite applications.
Downconverter See Down Converters
DP Differential phase; also decimal place
DPAK Discrete packaging
DPD Digital phase detector
DPDT Double-pole/double-throw
DPH Data pointer high
DPL Data pointer low
DPM Digital panel meter
DPOT See Digital Pot
DPS Data pointer select
DPST Double-pole/single-throw
DPWM Digitally adjusted pulse-width modulation
DQPSK Differential quadrature phase-shift keying
Drain One of the three terminals that comprise a FET. A voltage on the gate controls the current flow between the source and drain.
DRAM Dynamic RAM: Random-Access Memory that uses a continuous clock. Unlike SRAM, when DRAM is no longer clocked, its data is lost.
DRC Design-rule checking
DRL Daytime Running Lamps (DRLs) are white lights mounted on the front of an automobile. Mandated in many countries, they automatically switch on when the key is turned and are intended for daytime use, to increase the visibility of the automobile. They are typically built with LEDs.

See: High-Brightness LED Drivers

Drypack Drypack is a method for packing integrated circuits in a moisture-free environment. The device is baked and immediately sealed in a vacuum-sealed bag.

This process is reserved for package types which are especially susceptible to moisture intrusion. Maxim devices with MSL (Moisture Sensitivity Level) of 2 or higher require drypack. A part-number suffix of -D, +D, or #D at the end of the part number denotes products which ship with drypack. There is no price adder associated with drypacking products with MSL 2 or above.

DSL A mechanism for providing high-speed digital communications (e.g. Internet access) over a standard phone line.
DSLAM Digital Subscriber Line Access Multiplexer: a device which takes a number of ADSL subscriber lines and concentrates these to a single ATM line.
DSP See Digital Signal Processor
DSSP Digital-sensor signal processor
DSSS Direct-Sequence Spread Spectrum: A transmission technology used in WLAN (wireless LAN) transmissions where a data signal at the sending station is combined with a higher data-rate bit sequence, or chipping code, that divides the user data according to a spreading ratio.

See: "An Introduction to Direct-Sequence Spread-Spectrum Communications".

DTB Digital terrestrial broadcasting
DTE Data terminal equipment; interchangeable with DCE
DTMF Dual Tone Multiple Frequency (DTMF) is a signaling method developed by Bell Labs for sending telephone dialing information over the same analog, voice-quality phones lines that carry voice.

Each digit is encoded as the sum of two sine wave bursts, of different frequencies. The two-tone method was chosen because it can be reliably distinguished from voice and normal phone conversations are highly unlikely to falsely trigger the DTMF receiver.

DTMF was the basis for "TouchTone" (a former trademark of AT&T), the pushbutton system that replaced mechanical rotary dial telephones.

Dual In-line Package See DIP
Dual Mode Two modes of operation. Examples: In power circuits, the IC can deliver either a fixed 5V or an adjustable 1.3V to 16V source. In cellular phones, the IC operates in FM or CDMA mode, AMPS or TDMA mode, etc.

(Maxim Integrated trademarked term.)

Dual Phase Controller Switching regulator that employs dual-phase technique to reduce output noise and boost output current capability.
Dual Tone Multiple Frequency See DTMF
Dual-Band Dual-band refers to the capability of GSM network infrastructure and handsets to operate across two frequency bands.
Dual-Modulus Prescaler A Dual-Modulus Prescaler (DMP) is an important circuit block used in frequency synthesizers to divide the high-frequency signal from the voltage controlled oscillator (VCO) to a low-frequency signal by a predetermined divide ratio, either (N+1) or N, which is controlled by a swallow counter.

This low-frequency signal is then further divided by the main counter to the desired channel-spacing frequency which is then fed to the phase detector to form the closed feedback loop in frequency synthesizers.

DVB Digital Video Broadcast is a name for digital TV.
DVM Digital voltmeter
DWDM Dense Wave Division Multiplexing: The technology by which the frequencies of light carried on a single optical fiber are subdivided into discrete wavelengths, allowing for the greater transmission of data.
DXC Digital cross-connect
Dynamic RAM See DRAM
Dynamic Range The range, in dB, between the noise floor of a device and its defined maximum output level.