6

LTC1456

Resolution (n): Resolution is defined as the number of

digital input bits, n. It defines the number of DAC output

does not imply linearity.

when all bits are set to 1.

output when the DAC is loaded with all zeros. The output

amplifier can have a true negative offset, but because the

part is operated from a single supply, the output cannot go

below zero. If the offset is negative, the output will remain

near 0V resulting in the transfer curve shown in Figure 1.

The offset of the part is measured at the code that corre-

sponds to the maximum offset specification:

Least Significant Bit (LSB): One LSB is the ideal voltage

difference between two successive codes.

LSB = 4.095/4095 = 1mV

DEFI ITIO S

Integral Nonlinearity (INL): End-point INL is the maxi-

mum deviation from a straight line passing through the

end-points of the DAC transfer curve. Because the part

operates from a single supply and the output cannot go

below zero, the linearity is measured between full scale

and the code corresponding to the maximum offset speci-

fication. The INL error at a given input code is calculated

as follows:

INL

the given input code

Differential Nonlinearity (DNL): DNL is the difference

between the measured change and the ideal 1LSB change

between any two adjacent codes. The DNL error between

any two codes is calculated as follows:

DNL

= (

two adjacent codes

Digital Feedthrough: The glitch that appears at the analog

output caused by AC coupling from the digital inputs when

they change state. The area of the glitch is specified in

(nV)(sec).

DAC CODE

1456 F01

OUTPUT

VOLTAGE

NEGATIVE

OFFSET

0V

Figure 1. Effect of Negative Offset