ICM7712 Datasheet, PDF (7/9 Pages) IC MICROSYSTEMS – 12-Bit 1.2v Low Power Single DAC With Serial Interface and Voltage Output

ICM7712
APPLICATIONS INFORMATION
Power Supply Bypassing and Layout
Considerations
As in any precision circuit, careful consideration
has to be given to layout of the supply and
ground. The return path from the GND to the
supply ground should be short with low
impedance. Using a ground plane would be
ideal. The supply should have some bypassing
on it. A 10 µF tantalum capacitor in parallel
with a 0.1 µF ceramic with a low ESR can be
used. Ideally these would be placed as close as
possible to the device. Avoid crossing digital
and analog signals, specially the reference, or
running them close to each other.
Output Swing Limitations
The ideal rail-to-rail DAC would swing from
GND to VDD. However, offset and gain error
limit this ability. Figure 4 illustrates how a
negative offset error will affect the output. The
output will limit close to ground since this is
single supply part, resulting in a dead-band
area. As a larger input is loaded into the DAC
the output will eventually rise above ground.
This is why the linearity is specified for a
starting code greater than zero.
Figure 5 illustrates how a gain error or positive
offset error will affect the output when it is close
to VDD. A positive gain error or positive offset
will cause the output to be limited to the positive
supply voltage resulting in a dead-band of codes
close to full-scale.
VDD
DEADBAND
NEGATIVE
OFFSET
Figure 4. Effect of Negative Offset
OFFSET
VDD
AND GAIN
ERROR
DEAD BAND
POSITIVE
OFFSET
Figure 5. Effect of Gain Error and Positive Offset
Rev A1.5
ICmic reserves the right to change specifications without prior notice
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