DACDigital to analogue converter (DAC) as name indicates converts the digital values to analogue signal. The digital values are the binary values or states as on and off. DAC converts such information to an analogue signal containing infinitely many states. The analogue signal such as voltage is converted to digital values then if required the information is converted back to original data such as the digital values from computer are converted to analogue signals (audio frequency) by the modem.

DAC Performance specifications

Performance of a DAC is defined by the settling time, resolution, DNL (differential nonlinearity), INL (integral nonlinearity), power dissipation, and reference access. Settling time refers to the final value of output. The time a signal takes to settle down at output. Resolution is defined by the number of bits that can be converted to the analogue signal. Power dissipation is the amount of watts DAC consumes or dissipates during the operation. Reference access refers to the reference voltage. In some cases user supplies the voltage reference. In others internal power supply is the voltage reference.

DAC Errors

INL error is control system term. It refers to the transfer function. Transfer function is I / O function of a system in frequency domain (analogue) domain. INL error is the measured transfer function deviation from the ideal transfer function. Ideal and measured output values difference results in DNL error. Smaller the difference higher will be the performance. Various DAC chips indicate the errors in their specification.

DAC Outputs

DACs provide voltage outputs (+5 volts, 0-20 volts), currents outputs (0-10mA, 5- 20mA), Frequency outputs (AM, FM, and PWM), and resistance output. Moreover DACs allow timer and relay switch type outputs. Relay output means that the contact opens or closes depending upon the input state.

DAC Form Factor

Digital to Analogue converters come in various formats or Form Factors. These include integrated circuits or printed circuit boards, panel mount, chassis mount, and rack mount, modules, cards, DIN rails, and stand alone devices. Moreover some DACs come with rail-to-rail outputs, on-chip ESD (electrostatic discharge) protection, and single power supply support.

DAC Physical Layout

DACs are available in various types of Integrated Circuit (IC) packages. The most common are SIP (single in-line package), DIP (dual in-line package), BGA (ball grid array), QFP (quad flat package), and SOP (small outline package). BGAs are available in plastic ball grid array (TBGA) and tape ball grid array (TBGA). QFPs as low profile QFP (LPQFP), DIPs as plastic and ceramic (PDIP & CDIP), and SOP variants include TSOP (thin small outline package) and SSOP (shrink small outline package).

DAC Chip Architectures

Several DAC Chips are available based on various architectures. Common architecture choices include sigma delta architecture, resistive ladder network (R2R), resistor strings, and current steering architecture.