AD5686 datasheet(16/28 Pages) AD

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AD5686/AD5684

Data Sheet

Rev. A | Page 16 of 28

TERMINOLOGY

Relative Accuracy or Integral Nonlinearity (INL)

For the DAC, relative accuracy or integral nonlinearity is a

measurement of the maximum deviation, in LSBs, from a

straight line passing through the endpoints of the DAC transfer

function. A typical INL vs. code plot is shown in Figure 8.

Differential Nonlinearity (DNL)

Differential nonlinearity is the difference between the measured

change and the ideal 1 LSB change between any two adjacent

codes. A specified differential nonlinearity of ±1 LSB maximum

ensures monotonicity. These DACs are guaranteed monotonic

by design. A typical DNL vs. code plot can be seen in Figure 10.

Zero-Code Error

Zero-code error is a measurement of the output error when

zero code (0x0000) is loaded to the DAC register. Ideally, the

output should be 0 V. The zero-code error is always positive in

the AD5686/AD5684 because the output of the DAC cannot go

below 0 V due to a combination of the offset errors in the DAC

and the output amplifier. Zero-code error is expressed in mV. A

plot of zero-code error vs. temperature can be seen in Figure 16.

Full-Scale Error

Full-scale error is a measurement of the output error when full-

scale code (0xFFFF) is loaded to the DAC register. Ideally, the

output should be VDD − 1 LSB. Full-scale error is expressed in

percent of full-scale range (% of FSR). A plot of full-scale error

vs. temperature can be seen in Figure 15.

Gain Error

Gain error is a measurement of the span error of the DAC. It is

the deviation in slope of the DAC transfer characteristic from

the ideal expressed as % of FSR.

Offset Error Drift

Offset error drift is a measurement of the change in offset error

with a change in temperature. It is expressed in µV/°C.

Gain Temperature Coefficient

Gain temperature coefficient is a measurement of the change in

gain error with changes in temperature. It is expressed in ppm

of FSR/°C.

Offset Error

Offset error is a measurement of the difference between VOUT

(actual) and VOUT (ideal) expressed in mV in the linear region of

the transfer function. It can be negative or positive.

DC Power Supply Rejection Ratio (PSRR)

DC PSRR indicates how the output of the DAC is affected by

changes in the supply voltage. PSRR is the ratio of the change in

VOUT to a change in VDD for full-scale output of the DAC. It is

measured in mV/V. VREF is held at 2.5 V, and VDD is varied by

±10%.

Output Voltage Settling Time

The output voltage setting time is the amount of time it takes

for the output of a DAC to settle to a specified level for a ¼ to ¾

full-scale input change and is measured from the rising edge

of SYNC.

Digital-to-Analog Glitch Impulse

Digital-to-analog glitch impulse is the impulse injected into the

analog output when the input code in the DAC register changes

state. It is normally specified as the area of the glitch in nV-sec,

and is measured when the digital input code is changed by

1 LSB at the major carry transition (0x7FFF to 0x8000) (see

Figure 30).

Digital Feedthrough

Digital feedthrough is a measure of the impulse injected into the

analog output of the DAC from the digital inputs of the DAC,

but is measured when the DAC output is not updated. It is

specified in nV-sec and measured with a full-scale code change

on the data bus, that is, from all 0s to all 1s and vice versa.

Noise Spectral Density

Noise spectral density is a measurement of the internally

generated random noise. Random noise is characterized as a

spectral density (nV/√Hz). It is measured by loading the DAC

to midscale and measuring noise at the output. It is measured in

nV/√Hz.

DC Crosstalk

DC crosstalk is the dc change in the output level of one DAC

in response to a change in the output of another DAC. It is

measured with a full-scale output change on one DAC (or soft

power-down and power-up) while monitoring another DAC

kept at midscale. It is expressed in μV.

DC crosstalk due to load current change is a measurment of

the impact that a change in load current on one DAC has to

another DAC kept at midscale. It is expressed in μV/mA.

Digital Crosstalk

Digital crosstalk is the glitch impulse transferred to the output

of one DAC at midscale in response to a full-scale code change

(all 0s to all 1s and vice versa) in the input register of another

DAC. It is measured in standalone mode and is expressed in

nV-sec.

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