参数资料
| 型号： | AD8802ARZ-REEL |
| 厂商： | Analog Devices Inc |
| 文件页数： | 15/16页 |
| 文件大小： | 0K |
| 描述： | IC DAC 8BIT 12CH W/SD 20SOIC |
| 产品培训模块： | Data Converter Fundamentals DAC Architectures |
| 标准包装： | 1,000 |
| 系列： | TrimDAC® |
| 设置时间： | 600ns |
| 位数： | 8 |
| 数据接口： | 串行 |
| 转换器数目： | 12 |
| 电压电源： | 单电源 |
| 功率耗散（最大）： | 60µW |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 20-SOIC W |
| 包装： | 带卷 (TR) |
| 输出数目和类型： | 12 电压，单极 |
| 采样率（每秒）： | 1.7M |
AD8802/AD8804
REV. 0
–8–
...
DAC 12
ADDR
DECODE
SERIAL
REGISTER
CS
CLK
SDI
DAC 2
DAC 1
Figure 18. Equivalent Control Logic
The target DAC register is loaded with the last eight bits of the
serial data-word completing one DAC update. Twelve separate
12-bit data words must be clocked in to change all twelve out-
put settings.
All digital inputs are protected with a series input resistor and
parallel Zener ESD structure shown in Figure 19. Applies to
digital input pins CS, SDI, RS, SHDN, CLK
LOGIC
1k
Figure 19. Equivalent ESD Protection Circuit
Digital inputs can be driven by voltages exceeding the AD8802/
AD8804 VDD supply value. This allows 5 V logic to interface
directly to the part when it is operated at 3 V.
APPLICATIONS
Supply Bypassing
Precision analog products, such as the AD8802/AD8804, re-
quire a well filtered power source. Since the AD8802/AD8804
operate from a single +3 V to +5 V supply, it seems convenient
to simply tap into the digital logic power supply. Unfortunately,
the logic supply is often a switch-mode design, which generates
noise in the 20 kHz to 1 MHz range. In addition, fast logic gates
can generate glitches hundred of millivolts in amplitude due to
wiring resistances and inductances.
If possible, the AD8802/AD8804 should be powered directly
from the system power supply. This arrangement, shown in Fig-
ure 20, will isolate the analog section from the logic switching
transients. Even if a separate power supply trace is not available,
however, generous supply bypassing will reduce supply-line in-
duced errors. Local supply bypassing consisting of a 10
F tan-
talum electrolytic in parallel with a 0.1
F ceramic capacitor is
recommended (Figure 21).
TTL/CMOS
LOGIC
CIRCUITS
+5V
POWER SUPPLY
10F
TANT
0.1F
+
AD8802/
AD8804
Figure 20. Use Separate Traces to Reduce Power Supply
Noise
AD8802/
AD8804
VDD
DGND
10F
0.1F
+
+5V
Figure 21. Recommended Supply Bypassing for the
AD8802/AD8804
Buffering the AD8802/AD8804 Output
In many cases, the nominal 5 k
output impedance of the
AD8802/AD8804 is sufficient to drive succeeding circuitry. If a
lower output impedance is required, an external amplifier can
be added. Several examples are shown in Figure 22. One ampli-
fier of an OP291 is used as a simple buffer to reduce the output
resistance of DAC A. The OP291 was chosen primarily for its
rail-to-rail input and output operation, but it also offers opera-
tion to less than 3 V, low offset voltage, and low supply current.
The next two DACs, B and C, are configured in a summing
arrangement where DAC C provides the coarse output voltage
setting and DAC B can be used for fine adjustment. The inser-
tion of R1 in series with DAC B attenuates its contribution to
the voltage sum node at the DAC C output.
VH
VL
VREFH
VDD
+5V
GND
VREFL
DIGITAL INTERFACING
OMITTED FOR CLARITY
R1
100k
OP291
AD8802/
AD8804
SIMPLE BUFFER
0V TO 5V
SUMMER CIRCUIT
WITH FINE TRIM
ADJUSTMENT
VH
VL
VH
VL
Figure 22. Buffering the AD8802/AD8804 Output
Increasing Output Voltage Swing
An external amplifier can also be used to extend the output volt-
age swing beyond the power supply rails of the AD8802/AD8804.
This technique permits an easy digital interface for the DAC,
while expanding the output swing to take advantage of higher
voltage external power supplies. For example, DAC A of Fig-
ure 23 is configured to swing from –5 V to +5 V. The actual
output voltage is given by:
VOUT = 1 +
R
F
RS
×
D
256
× 5V
()–5V
where D is the DAC input value (i.e., 0 to 255). This circuit can
be combined with the “fine/coarse” circuit of Figure 22 if, for
example, a very accurate adjustment around 0 V is desired.
相关PDF资料 |
PDF描述 |
|---|---|
| AD8804ARZ-REEL | IC DAC 8BIT 12CH W/SD 20SOIC |
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| V300A12H400BG | CONVERTER MOD DC/DC 12V 400W |
| AD5317BRUZ-REEL7 | IC DAC 10BIT QUAD W/BUFF 16TSSOP |
| VI-BN4-MV-F1 | CONVERTER MOD DC/DC 48V 150W |
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