REV. 0

AD7398/AD7399

–7–

TERMINOLOGY

Relative Accuracy, INL

For the DAC, relative accuracy or integral nonlinearity (INL) is

a measure of the maximum deviation, in LSBs, from a straight

line passing through the endpoints of the DAC transfer function.

A typical INL versus code plot can be seen in TPC 1.

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 maxi-

mum ensures monotonicity. TPC 3 illustrates a typical DNL

versus code plot.

Zero-scale error is a measure of the output voltage error from

zero voltage when zero code is loaded to the DAC register.

Full-scale error is a measure of the output voltage error from full-

scale voltage when full-scale code is loaded to the DAC register.

This is a measure of the change in full-scale error with a change

in temperature. It is expressed in ppm/

°C or mV/°C.

DAC Glitch Impulse, Q

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-s

and is measured when the digital input code is changed by 1 LSB

at the major carry transition (midscale transition). A plot of the

glitch impulse is shown in TPC 10.

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.

CS is held

high, while the CLK and SDI signals are toggled. It is speci-

fied in nV-s and is measured with a full-scale code change on

the data bus, i.e., from all 0s to all 1s and vice versa. A typi-

cal plot of digital feedthrough is shown in TPC 11.

Power Supply Sensitivity, PSS

This specification indicates how the output of the DAC is

affected by changes in the power supply voltage. Power supply

sensitivity is quoted in terms of % change in output per %

by

±10%.

the DAC output when the DAC is loaded with all 0s. A 100 kHz,

in dB or mV p-p.