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参数资料
| 型号： | AD8802 |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | 12 Channel, 8-Bit TrimDACs with Power Shutdown |
| 中文描述： | 12通道，8位与电源关断TrimDACs |
| 文件页数： | 8/16页 |
| 文件大小： | 432K |
| 代理商： | AD8802 |
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 V
DD
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
μ
F tan-
talum electrolytic in parallel with a 0.1
μ
F ceramic capacitor is
recommended (Figure 21).
TTL/CMOS
LOGIC
CIRCUITS
+5V
POWER SUPPLY
10μF
TANT
0.1μF
+
AD8804
Figure 20. Use Separate Traces to Reduce Power Supply
Noise
AD8802/
AD8804
V
DD
DGND
10μF
0.1μF
+
+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.
V
H
V
L
V
REFH
V
DD
+5V
GND
V
REFL
DIGITAL INTERFACING
OMITTED FOR CLARITY
R1
100k
OP291
AD8802/
AD8804
SIMPLE BUFFER
0V TO 5V
SUMMER CIRCUIT
WITH FINE TRIM
ADJUSTMENT
V
H
V
L
V
H
V
L
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:
V
OUT
=
1
+
R
F
R
S
D
256
×
5
V
(
)
– 5
V
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 |
|---|---|
| AD8802AN | 12 Channel, 8-Bit TrimDACs with Power Shutdown |
| AD8802AR | 12 Channel, 8-Bit TrimDACs with Power Shutdown |
| AD8802ARU | 12 Channel, 8-Bit TrimDACs with Power Shutdown |
| AD8804 | 12 Channel, 8-Bit TrimDACs with Power Shutdown(12通道,带电源关断8位D/A转换器) |
| AD8842 | Precision, Quad, SPST Analog Switches |
相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8802AN | 制造商:Analog Devices 功能描述:DAC 12-CH R-2R 8-bit 20-Pin PDIP N Tube 制造商:Analog Devices 功能描述:SEMICONDUCTORSLINEAR |
| AD8802ANZ | 功能描述:IC DAC 8BIT 12CH W/SD 20DIP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:TrimDAC® 标准包装:2,400 系列:- 设置时间:- 位数:18 数据接口:串行 转换器数目:3 电压电源:模拟和数字 功率耗散（最大）:- 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:36-TFBGA 供应商设备封装:36-TFBGA 包装:带卷 (TR) 输出数目和类型:* 采样率（每秒）:* |
| AD8802AR | 功能描述:IC DAC 8BIT 12CH W/SD 20-SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:TrimDAC® 标准包装:47 系列:- 设置时间:2µs 位数:14 数据接口:并联 转换器数目:1 电压电源:单电源 功率耗散（最大）:55µW 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:28-SSOP（0.209"，5.30mm 宽） 供应商设备封装:28-SSOP 包装:管件 输出数目和类型:1 电流，单极；1 电流，双极 采样率（每秒）:* |
| AD8802AR-REEL | 制造商:Analog Devices 功能描述:DAC 12-CH R-2R 8-bit 20-Pin SOIC W T/R |
| AD8802ARU | 功能描述:IC DAC 8BIT 12CH W/SD 20-TSSOP RoHS:否 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:TrimDAC® 标准包装:47 系列:- 设置时间:2µs 位数:14 数据接口:并联 转换器数目:1 电压电源:单电源 功率耗散（最大）:55µW 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:28-SSOP（0.209"，5.30mm 宽） 供应商设备封装:28-SSOP 包装:管件 输出数目和类型:1 电流，单极；1 电流，双极 采样率（每秒）:* |
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