11

LTC1657/LTC1657L

Rail-to-Rail Output Considerations

In any rail-to-rail DAC, the output swing is limited to

voltages 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

error (FSE) is positive, the output for the highest codes

Offset and linearity are defined and tested over the region

of the DAC transfer function where no output limiting can

occur.

Figure 2. Effects of Rail-to-Rail Operation On a DAC Transfer Curve. (a) Overall Transfer Function (b) Effect of Negative

1657 F02

INPUT CODE

(b)

OUTPUT

VOLTAGE

NEGATIVE

OFFSET

0V

32768

0

65535

INPUT CODE

OUTPUT

VOLTAGE

(a)

(c)

INPUT CODE

OUTPUT

VOLTAGE

POSITIVE

FSE

APPLICATIO S I FOR ATIO