7

LTC1458/LTC1458L

B11 A

MSB

B11 C

MSB

B0 B

LSB

B0 D

LSB

B11 A

CURRENT WORD

CLK

CS/LD

1458 TD

B0 D

PREVIOUS WORD

B11 A

PREVIOUS WORD

B10 A

PREVIOUS WORD

B0 B

PREVIOUS WORD

B11 C

PREVIOUS WORD

B0 D

PREVIOUS WORD

TI I G DIAGRA

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.

DEFI ITIO S

DAC CODE

1458 F01

OUTPUT

VOLTAGE

NEGATIVE

OFFSET

0V

Figure 1. Effect of Negative Offset

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.

Nominal LSBs:

LTC1458

LSB = 4.095V/4095 = 1mV

LTC1458L

LSB = 2.5V/4095 = 0.610mV

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

specification. The INL error at a given input code is

calculated as follows:

INL

the given input code