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PDF AD7845 Data sheet ( Hoja de datos )
| Número de pieza | AD7845 | |
| Descripción | LC2MOS Complete 12-Bit Multiplying DAC | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AD7845 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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LC2MOS
Complete 12-Bit Multiplying DAC
AD7845
FEATURES
12-Bit CMOS MDAC with Output Amplifier
4-Quadrant Multiplication
Guaranteed Monotonic (TMIN to TMAX)
Space-Saving 0.3" DIPs and 24- or 28-Terminal Surface
Mount Packages
Application Resistors On Chip for Gain Ranging, etc.
Low Power LC2MOS
APPLICATIONS
Automatic Test Equipment
Digital Attenuators
Programmable Power Supplies
Programmable Gain Amplifiers
Digital-to-4–20 mA Converters
FUNCTIONAL BLOCK DIAGRAM
GENERAL DESCRIPTION
The AD7845 is the industry’s first 4-quadrant multiplying D/A
converter with an on-chip amplifier. It is fabricated on the
LC2MOS process, which allows precision linear components
and digital circuitry to be implemented on the same chip.
The 12 data inputs drive latches which are controlled by stan-
dard CS and WR signals, making microprocessor interfacing
simple. For stand-alone operation, the CS and WR inputs can
be tied to ground, making all latches transparent. All digital
inputs are TTL and 5 V CMOS compatible.
The output amplifier can supply ± 10 V into a 2 kΩ load. It is
internally compensated, and its input offset voltage is low due to
laser trimming at wafer level. For normal operation, RFB is tied
to VOUT, but the user may alternatively choose RA, RB or RC to
scale the output voltage range.
PRODUCT HIGHLIGHTS
1. Voltage Output Multiplying DAC
The AD7845 is the first DAC which has a full 4-quadrant
multiplying capability and an output amplifier on chip. All
specifications include amplifier performance.
2. Matched Application Resistors
Three application resistors provide an easy facility for gain
ranging, voltage offsetting, etc.
3. Space Saving
The AD7845 saves space in two ways. The integration of the
output amplifier on chip means that chip count is reduced.
The part is housed in skinny 24-lead 0.3" DIP, 28-terminal
LCC and PLCC and 24-terminal SOIC packages.
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999
1 page  
Typical Performance Characteristics–AD7845
Figure 2. Frequency Response, G = –1 Figure 3. Output Voltage Swing vs.
Resistive Load
Figure 4. Noise Spectral Density
Figure 5. THD vs. Frequency
Figure 8. Unity Gain Inverter Pulse
Response (Large Signal)
Figure 6. Typical AD7845 Linearity
vs. Power Supply
Figure 9. Unity Gain Inverter Pulse
Response (Small Signal)
Figure 7. Multiplying Feedthrough
Error vs. Frequency
80
70
60
50
40
30
20
10
0
–10
–20
0 2 4 6 8 10 12 14 16 18 20
TIME – s
Figure 10. Digital-to-Analog Glitch
Impulse (All 1s to All 0s Transition)
REV. B
–5–
5 Page 
Figure 23 and 24 are the interface circuits for the Z80 and
MC6809 microprocessors. Again, these use the same basic
format as the 8085A interface.
AD7845
DIGITAL FEEDTHROUGH
In the preceding interface configurations, most digital inputs to
the AD7845 are directly connected to the microprocessor bus.
Even when the device is not selected, these inputs will be con-
stantly changing. The high frequency logic activity on the bus
can feed through the DAC package capacitance to show up as
noise on the analog output. To minimize this digital feedthrough
isolate the DAC from the noise source. Figure 25 shows an
interface circuit which uses this technique. All data inputs are
latched from the busy by the CS signal. One may also use other
means, such as peripheral interface devices, to reduce the digital
feedthrough.
Figure 23. AD7845 to Z80 Interface
Figure 25. AD7845 Interface Circuit Using Latches to
Minimize Digital Feedthrough
Figure 24. MC6809 Interface
REV. B
–11–
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet AD7845.PDF ] | |
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