LTC1654IGN datasheet(12/16 Pages) LINER

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LTC1654

1654fb

Figure 3. Effect of Negative Offset

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

difference between two successive codes.

LSB = (VFS – VOS)/(2n – 1) = (VFS – VOS)/16383

Nominal LSBs:

LTC1654 LSB = 4.09575V/16383 = 250

µV

Zero-Scale Error (ZSE): The output voltage when the

DAC is loaded with all zeros. Since this is a single supply

part, this value cannot be less than 0V.

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 low code

kL and full scale. The INL error at a given input code is

calculated as follows:

INL

= [VOUT – VOS – (VFS – VOS)(code/16383)]/LSB

VOUT = The output voltage of the DAC measured at the

given input code

Differential Nonlinearity (DNL): DNL is the difference

between the measured change and the ideal one LSB

change between any two adjacent codes. The DNL error

between any two codes is calculated as follows:

DNL

= (

∆VOUT – LSB)/LSB

∆VOUT = The measured voltage difference between

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 • s.

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

digital input bits (n). It is also the number of DAC output

states (2n) that divide the full-scale range. Resolution does

not imply linearity.

Full-Scale Voltage (VFS): This is the output of the DAC

when all bits are set to 1.

Voltage Offset Error (VOS): Normally, DAC offset is the

voltage at the output when the DAC is loaded with all zeros.

The DAC can have a true negative offset, but because the

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

below 0V. If the offset is negative, the output will remain

near 0V resulting in the transfer curve shown in Figure 3.

Therefore, the offset of the part is measured at low code kL:

OUT

⎛

⎝⎜

⎞

⎠⎟

() –

()(

)

–

DAC CODE

1654 F01

OUTPUT

VOLTAGE

NEGATIVE

OFFSET

DEFI ITIO S

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