Output Voltage; Offset Error; Gain Error - Linear Technology LTC1592 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 572
EXPERIMENTS

OUTPUT VOLTAGE

The offset and gain errors of the LT1592 are rela-
tively easy to measure. These errors are on the or-
der of several LSBs, so a voltmeter with an accu-
16
racy of 5V/2 = 76µV, or 5 digits, is required. Note
that errors are dependent on several factors, includ-
ing reference error, amplifier offset, DAC errors, and
errors in measurement equipment.

OFFSET ERROR

Offset error is the output voltage when the digital
code for zero output is loaded into the DAC. For the
unipolar ranges (0-5V, 0-10V) the code for zero
output is 0x0000. For the symmetric bipolar ranges
(+/-2.5V, +/-5V, +/-10V) it is 0x8000. For the –2.5 to
+7.5V range, it is 0x4000.

GAIN ERROR

Gain error is the error in slope of the DAC output,
and is calculated by subtracting the zero code error
from the maximum code error. For instance, in the
–2.5 to 7.5V range a certain LTC1592 produces –
2.50004V at zero code and +7.50009 at maximum
code, the gain error is 0.00009V – (-0.00004V) =
130µV.
The error in LSBs is 130µV * 2
16-BIT SOFTSPAN DAC
16
/ 10 = 0.85LSB.
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