AD8065 datasheet(21/60 Pages) AD

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Data Sheet

AD3551R

TERMINOLOGY

analog.com

Rev. 0 | 21 of 60

Relative Accuracy or Integral Nonlinearity (INL)

For the DAC, relative accuracy or integral nonlinearity is a meas-

urement of the maximum deviation, in LSBs, from a straight line

passing through the endpoints of the DAC transfer function. See

Figure 13 for a typical INL vs. code plot.

Differential Nonlinearity (DNL)

Differential nonlinearity is the difference between the measured

change and the ideal 1 LSB change between any two adjacent

codes. See Figure 14 for a typical DNL vs. code plot.

Offset Error

Offset error is the vertical deviation from the ideal transfer func-

tion after the gain error has been compensated. Offset error is

expressed in mV. In the AD3551R, offset error is measured at

midscale. The comparison between the ideal output and the actual

output is performed at midscale.

Offset Error Drift

The offset error drift is a measurement of the relative variation of

the offset with temperature. It is expressed in ppm/°C. Total offset at

a given temperature is calculated as

OffsetT=Offset25°C+TC×T−25×VRANGE

106

Full-Scale and Zero-Scale Error

These errors measure the deviation from the ideal value at full

scale and zero scale, at 25°C. The error is expressed as % of

full-scale range (FSR). In the case of the AD3551R, the ideal

value is calculated as the average of a sufficiently high number of

samples.

Full-Scale and Zero-Scale Error Drift

These parameters measure the variation of the zero-scale and

full-scale voltage as a function of the temperature, relative to the

ideal zero-scale and full-scale voltages. They are expressed in

ppm/°C. The total deviation over temperature is calculated using

the same formula used for the offset.

DC PSRR and AC PSRR

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 the supplies for midscale output of the DAC. It is

measured in dB. VREF is held at 2.5 V, and the supplies are varied

by ±200 mV p-p.

Output Voltage Settling Time

Output voltage settling time is the amount of time it takes for the

output of a DAC to settle to a specified level for a given step

change. See Figure 52 through Figure 57 for typical plots of small

and large signal settling, respectively.

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.

See Figure 48 for a typical glitch impulse plot.

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 it is

measured when the DAC output is not updated. Digital feedthrough

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

on the data bus, which means from all 0s to all 1s and vice versa.

See Figure 50 for a typical digital feedthrough plot.

Output Noise Spectral Density

Noise spectral density is a measurement of the internally generated

random noise. Noise is measured at the DAC output when it is

loaded with the midscale code. It is measured in nV/

Hz.See

Figure 32 for a plot of noise spectral density. The noise of the

internal reference is also characterized in Figure 60.

Total Harmonic Distortion (THD)

THD is the difference between an ideal sine wave and the attenuat-

ed version using the DAC. The sine wave is used as the reference

for the DAC, and the THD is a measurement of the harmonics

present on the DAC output. It is measured in dB.

Voltage Reference Temperature Coefficient

(TC)

Voltage reference TC is a measure of the change in the reference

output voltage with a change in temperature. The reference TC

is calculated using the box method, which defines the TC as the

maximum change in the reference output over a given temperature

range expressed in ppm/°C, as shown in the following equation:

TC = VREF_MAX − VREF_MIN

VREF_NOM × TEMP_RANGE

×106 (1)

where:

VREF_MAX is the maximum reference output measured over the total

temperature range.

VREF_MIN is the minimum reference output measured over the total

temperature range.

VREF_NOM is the nominal reference output voltage, 2.5 V.

TEMP_RANGE is the specified temperature range, −40°C to

+105°C.

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