REV. B

AD1555/AD1556

–12–

TERMINOLOGY

DYNAMIC RANGE

Dynamic range is the ratio of the rms value of the full scale to

the total rms noise measured with the inputs shorted together

value for dynamic range is expressed in decibels.

SIGNAL-TO-NOISE RATIO (SNR)

SNR is the ratio of the rms value of the full-scale signal to the

total rms noise in the bandwidth from 3 Hz to the Nyquist fre-

TOTAL HARMONIC DISTORTION (THD)

THD is the ratio of the rms sum of all the harmonic components

input signal. The value for THD is expressed in decibels.

INTERMODULATION DISTORTION (IMD)

IMD is the ratio of the rms sum of two sine wave signals of

30 Hz and 50 Hz which are each 6 dB down from full scale to

the rms sum of all intermodulation components within the

for IMD is expressed in decibels.

OFFSET

The offset is the difference between the ideal midscale input volt-

age (0 V) and the actual voltage producing the midscale output

code (code 000000H) at the output of the AD1556. The offset

specification is referred to the output. This offset is intentionally

set at a nominal value of –60 mV (see Sigma-Delta Modulator

section). The value for offset is expressed in mV.

OFFSET ERROR DRIFT

The change of the offset over temperature. It is expressed in mV.

GAIN ERROR

The gain error is the ratio of the difference between the actual

gain and the ideal gain to the ideal gain. The actual gain is the

ratio of the output difference obtained with a full-scale analog

input (

±2.25 V) to the full-scale span (4.5 V) after correction of

the effects of the external components. It is expressed in %.

GAIN ERROR STABILITY OVER TEMPERATURE

The change of the gain error over temperature. It is expressed

in %.