AD5405 datasheet(13/24 Pages) AD

13 / 24 page

AD5405

Rev. 0 | Page 13 of 24

TERMINOLOGY

Relative Accuracy

Relative accuracy or endpoint nonlinearity is a measure of the

maximum deviation from a straight line passing through the

endpoints of the DAC transfer function. It is measured after

adjusting for zero and full scale and is normally expressed in

LSBs or as a percentage of full-scale reading.

Differential Nonlinearity

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 max over

the operating temperature range ensures monotonicity.

Gain Error

Gain error or full-scale error is a measure of the output error

between an ideal DAC and the actual device output. For this

DAC, ideal maximum output is VREF − 1 LSB. Gain error of the

DACs is adjustable to zero with external resistance.

Output Leakage Current

Output leakage current is current that flows in the DAC ladder

switches when these are turned off. For the IOUT1 terminal, it can

be measured by loading all 0s to the DAC and measuring the

IOUT1 current. Minimum current flows in the IOUT2 line when

the DAC is loaded with all 1s.

Output Capacitance

Capacitance from IOUT1 or IOUT2 to AGND.

Output Current Settling Time

This is the amount of time it takes for the output to settle to a

specified level for a full-scale input change. For this device, it is

specified with a 100 Ω resistor to ground.

Digital to Analog Glitch lmpulse

The amount of charge injected from the digital inputs to the

analog output when the inputs change state. This is typically

specified as the area of the glitch in either pA-secs or nV-secs

depending upon whether the glitch is measured as a current or

voltage signal.

Digital Feedthrough

When the device is not selected, high frequency logic activity on

the device’ s digital inputs is capacitively coupled through the

device to show up as noise on the IOUT pins and subsequently

into the following circuitry. This noise is digital feedthrough.

Multiplying Feedthrough Error

This is the error due to capacitive feedthrough from the DAC

reference input to the DAC IOUT1 terminal, when all 0s are

loaded to the DAC.

Digital Crosstalk

This is the glitch impulse transferred to the outputs of one

DAC in response to a full-scale code change (all 0s to all 1s,

and vice versa) in the input register of the other DAC. It is

expressed in nV-s.

Analog Crosstalk

This is the glitch impulse transferred to the output of one DAC

due to a change in the output of another DAC. It is measured by

loading one of the input registers with a full-scale code change

(all 0s to all 1s, and vice versa), while keeping LDAC high. Then

pulse LDAC low and monitor the output of the DAC whose

digital code was not changed. The area of the glitch is expressed

in nV-s.

Channel to Channel Isolation

This refers to the proportion of input signal from one DAC’s

reference input which appears at the output of the other DAC,

and is expressed in dBs.

Total Harmonic Distortion (THD)

The DAC is driven by an ac reference. The ratio of the rms sum

of the harmonics of the DAC output to the fundamental value is

the THD. Usually only the lower-order harmonics are included,

such as the second to the fifth.

(

)

log

THD

Intermodulation Distortion

The DAC is driven by two combined sine wave references

of frequencies fa and fb. Distortion products are produced

at sum and difference frequencies of mfa ± nfb where m, n = 0,

1, 2, 3,... Intermodulation terms are those for which m or n is

not equal to zero. The second-order terms include (fa + fb)

and (fa − fb) and the third-order terms are (2fa + fb), (2fa − fb),

(f + 2fa + 2fb) and (fa − 2fb). IMD is defined as

(

)

fundamenta

the

amplitude

rms

products

distortion

diff

and

sum

the

sum

rms

IMD

log

Compliance Voltage Range

The maximum range of (output) terminal voltage for which the

device provides the specified characteristics.

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