Datasheet

LTC1659
9
1659fa
APPLICATIONS INFORMATION
Rail-to-Rail Output Considerations
In any rail-to-rail DAC, the output swing is limited to volt-
ages within the supply range.
If the DAC offset is negative, the output for the lowest
codes limits at 0V as shown in Figure 1b.
Similarly, limiting can occur near full scale when the REF
pin is tied to V
CC
. If V
REF
= V
CC
and the DAC full-scale
Figure 1. Effects of Rail-to-Rail Operation on a DAC Transfer Curve
(1a) Overall Transfer Function
(1b) Effect of Negative Offset for Codes Near Zero Scale
(1c) Effect of Positive Full-Scale Error for Input Codes Near Full Scale When V
REF
= V
CC
error (FSE) is positive, the output for the highest codes
limits at V
CC
as shown is Figure 1c. No full-scale limiting
can occur if V
REF
is less than V
CC
– FSE.
Offset and linearity are defi ned and tested over the region
of the DAC transfer function where no output limiting can
occur.
1659 F01
INPUT CODE
(1b)
OUTPUT
VOLTAGE
NEGATIVE
OFFSET
0V
20480 4095
INPUT CODE
OUTPUT
VOLTAGE
(1a)
V
REF
= V
CC
V
REF
= V
CC
(1c)
INPUT CODE
OUTPUT
VOLTAGE
POSITIVE
FSE