ICM7722 Datasheet, PDF (8/10 Pages) IC MICROSYSTEMS – 12-Bit 1.2v Low Power Dual DAC With Serial Interface and Voltage Output

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.
VDD
DEADBAND
NEGATIVE
OFFSET
ICM7722
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.
Figure 4. Effect of Negative Offset
VDD
OFFSET
AND GAIN
ERROR
DEAD BAND
POSITIVE
OFFSET
Figure 5. Effect of Gain Error and Positive Offset
Rev A0.1
ICmic reserves the right to change specifications without prior notice
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