LTC1655/LTC1655L
U
W U U
APPLICATIONS INFORMATION
Rail-to-Rail Output Considerations
error (FSE) is positive, the output for the highest codes
limits at VCC as shown in Figure 1c. No full-scale limiting
can occur if VREF is less than (VCC – FSE)/2.
In any rail-to-rail DAC, the output swing is limited to
voltages within the supply range.
Offset and linearity are defined and tested over the region
of the DAC transfer function where no output limiting can
occur.
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 VCC/2. If VREF = VCC/2 and the DAC full-scale
POSITIVE
FSE
V
CC
V
= V /2
CC
OUTPUT
VOLTAGE
REF
INPUT CODE
(1c)
V
CC
V
= V /2
CC
OUTPUT
VOLTAGE
REF
0
32768
65535
INPUT CODE
(1a)
OUTPUT
VOLTAGE
0V
NEGATIVE
OFFSET
INPUT CODE
1655/55L F01
(1b)
Figure 1. Effects of Rail-to-Rail Operation On a DAC Transfer Curve. (a) Overall Transfer Function (b) Effect of Negative
Offset for Codes Near Zero Scale (c) Effect of Positive Full-Scale Error for Input Codes Near Full Scale When VREF = VCC/2
10
Linear [ Linear ]
