Pentek 6210 Operating Manual page 159

DEFI ITIO S
Resolution (n): Resolution is defined as the number of
digital input bits, n. It defines the number of DAC output
n
states (2 ) that divide the full-scale range. The resolution
does not imply linearity.
Full-Scale Voltage (V ): This is the output of the DAC
FS
when all bits are set to 1.
Voltage Offset Error (V
OS
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 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:
– [(Code × V
V = V
OS OUT
Least Significant Bit (LSB): One LSB is the ideal voltage
difference between two successive codes.
n
LSB = (V – V )/(2
FS OS
Nominal LSBs:
LTC1451 LSB = 4.095V/4095 = 1mV
LTC1452 LSB = V(REF)/4095
LTC1453 LSB = 2.5V/4095 = 0.610mV
): Normally, DAC offset is the
n
)/(2 – 1)]
FS
– 1) = (V – V )/4095
FS OS
OUTPUT
VOLTAGE
0V
NEGATIVE
OFFSET
Figure 1. Effect of Negative Offset
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 = [V – V
OUT
V = The output voltage of the DAC measured at
OUT
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 = (∆V
OUT
∆V
= The measured voltage difference between
OUT
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
1451/2/3 F01
LTC1451
LTC1452/LTC1453
– (V – V )(code/4095)]/LSB
OS FS OS
– LSB)/LSB
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