參數(shù)資料
型號: DAC7621
元件分類: 外設(shè)及接口
英文描述: Single Supply RS232C Line Driver/Receiver(?????μ?o?RS232C ?o?????????¨???2???2??????)
中文描述: 單電源RS232C接口線路驅(qū)動器/接收器(單電源RS232C接口線收發(fā)器(2發(fā)2收))
文件頁數(shù): 11/11頁
文件大小: 458K
代理商: DAC7621
11
DAC7621
FIGURE 4. Suggested Power and Ground Connections for a DAC7621 Sharing a +5V Supply with a Digital System with a
Single Ground Plane.
APPLICATIONS
POWER AND GROUNDING
The DAC7621 can be used in a wide variety of situations—
from low power, battery operated systems to large-scale
industrial process control systems. In addition, some appli-
cations require better performance than others, or are par-
ticularly sensitive to one or two specific parameters. This
diversity makes it difficult to define definite rules to follow
concerning the power supply, bypassing, and grounding.
The following discussion must be considered in relation to
the desired performance and needs of the particular system.
A precision analog component requires careful layout, ad-
equate bypassing, and a clean, well-regulated power supply.
As the DAC7621 is a single-supply, +5V component, it will
often be used in conjunction with digital logic,
microcontrollers, microprocessors, and digital signal proces-
sors. The more digital logic present in the design and the
higher the switching speed, the more difficult it will be to
achieve good performance.
The DAC7621 has separate analog ground and digital ground
pins. The current through DGND is mostly switching tran-
sients and are up to 4mA peak in amplitude. The current
through AGND is typically 0.5mA.
For best performance, separate analog and digital ground
planes with a single interconnection point to minimize
ground loops. The analog pins are located adjacent to each
other to help isolate analog from digital signals. Analog
signals should be routed as far as possible from digital
signals and should cross them at right angles. A solid analog
ground plane around the D/A package, as well as under it in
the vicinity of the analog and power supply pins, will isolate
the D/A from switching currents. It is recommended that
DGND and AGND be connected directly to the ground
planes under the package.
If several DAC7621s are used, or if sharing supplies with
other components, connecting the AGND and DGND lines
together at the power supplies once, rather than at each chip,
may produce better results.
The power applied to V
DD
should be well regulated and low-
noise. Switching power supplies and DC/DC converters 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 V
DD
and V
OUT
.
As with the GND connection, V
DD
should be connected to
a +5V power supply plane or trace that is separate from the
connection for digital logic until they are connected at the
power entry point. In addition, the 10
μ
F and 0.1
μ
F capaci-
tors shown in Figure 4 are strongly recommended and
should be installed as close to V
DD
and ground as possible.
In some situations, additional bypassing may be required
such as a 100
μ
F electrolytic capacitor or even a “Pi” filter
made up of inductors and capacitors—all designed to essen-
tially lowpass filter the +5V supply, removing the high
frequency noise (see Figure 4).
+
+5V
GND
100
μ
F
Digital Circuits
+5V
GND
+5V
Power
Supply
Other
Analog
Components
V
DD
AGND
DGND
DAC7621
+
10
μ
F
0.1
μ
F
Optional
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