DAC7741Y Burr-Brown Corporation, DAC7741Y Datasheet - Page 17

• Manufacturer Part Number: DAC7741Y
• Description: 16-Bit/ Single Channel DIGITAL-TO-ANALOG CONVERTER With Internal Reference and Parallel Interface
• Manufacturer: Burr-Brown Corporation

NOISE PERFORMANCE
Increased noise performance of the DAC output can be
achieved by filtering the voltage reference input to the
DAC7741. Figure 10 shows a typical internal reference filter
schematic. A low-pass filter applied between the REF
REF
output amplifier. The REF
50 A so care should be taken in order to avoid overloading
the internal reference output
FIGURE 10. Internal Reference Filter.
DAC7741
SBAS248A
IN
(Other Connections
Omitted for Clarity)
pins can increase noise immunity at the DAC and
1 F
100k
43
44
45
46
47
48
OUT
RSTSEL
REFEN
REF
REFADJ
REF
NC
.
pin can source a maximum of
OUT
IN
OUT
and
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LAYOUT
A precision analog component requires careful layout, adequate
bypassing, and clean, well-regulated power supplies. The
DAC7741 offers separate digital and analog supplies, as it will
often be used in close proximity with digital logic, microcontrollers,
microprocessors, and digital signal processors. The more digital
logic present in the design and the higher the switching speed,
the more important it will become to separate the analog and
digital ground and supply planes at the device.
Since the DAC7741 has both analog and digital ground pins,
return currents can be better controlled and have less effect
on the DAC output error. Ideally, AGND would be connected
directly to an analog ground plane and DGND to the digital
ground plane. The analog ground plane would be separate
from the ground connection for the digital components until
they were connected at the power entry point of the system.
The voltages applied to V
and low noise. Switching power supplies and dc/dc convert-
ers will often have high-frequency glitches or spikes riding on
the output voltage. In addition, digital components can create
similar high-frequency spikes as their internal logic switches
states. This noise can easily couple into the DAC output
voltage through various paths between the power connec-
tions and analog output.
In addition, a 1 F to 10 F bypass capacitor in parallel with a
0.1 F bypass capacitor is strongly recommended for each
supply input. In some situations, additional bypassing may
be required, such as a 100 F electrolytic capacitor or even
a "Pi" filter made up of inductors and capacitors–all designed
to essentially low-pass filter the analog supplies, removing
any high frequency noise components.
CC
and V
SS
should be well regulated
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