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| 型号： | AD7845JN |
| 厂商： | Analog Devices Inc |
| 文件页数： | 11/12页 |
| 文件大小： | 0K |
| 描述： | IC DAC 12BIT MULTIPLYING 24-DIP |
| 产品培训模块： | Data Converter Fundamentals DAC Architectures |
| 产品变化通告： | Product Discontinuance 27/Oct/2011 |
| 标准包装： | 15 |
| 设置时间： | 5µs |
| 位数： | 12 |
| 数据接口： | 并联 |
| 转换器数目： | 1 |
| 电压电源： | 双 ± |
| 功率耗散（最大）： | 150mW |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 24-DIP（0.300"，7.62mm） |
| 供应商设备封装： | 24-PDIP |
| 包装： | 管件 |
| 输出数目和类型： | 1 电压，单极；1 电压，双极 |
| 采样率（每秒）： | 200k |
AD7845
REV. B
–8–
APPLI
CATIONS CIRCUITS
PROGRAMMABLE GAIN AMPLIFIER (PGA)
The AD7845 performs a PGA function when connected as in
Figure 15. In this configuration, the R-2R ladder is connected
in the amplifier feedback loop. RFB is the amplifier input resis-
tor. As the code decreases, the R-2R ladder resistance increases
and so the gain increases.
VOUT = –VIN ×
R
DAC
D
×
1
R
FB
,
D
= 0 to
4095
4096
= –VIN ×
R
DAC
D
×
1
R
DAC
=
–V
IN
D
, since RFB = RDAC
Figure 15. AD7845 Connected as PGA
As the programmed gain increases, the error and noise also
increase. For this reason, the maximum gain should be limited
to 256. Table III shows gain versus code.
Note that instead of using RFB as the input resistor, it is also
possible to use combinations of the other application resistors,
RA, RB and RC. For instance, if RB is used instead of RFB, the
gain range for the same codes of Table II now goes from l/2
to 128.
Table III. Gain and Error vs. Input Code for Figure 15
Digital Inputs
Gain
Error (%)
1111
4096/4095
≈ 10.04
1000
0000
2
0.07
0100
0000
4
0.13
0010
0000
8
0.26
0001
0000
16
0.51
0000
1000
0000
32
1.02
0000
0100
0000
64
2.0
0000
0010
0000
128
4.0
0000
0001
0000
256
8.0
PROGRAMMABLE CURRENT SOURCES
The AD7845 is ideal for designing programmable current
sources using a minimum of external components. Figures 16
and 17 are examples. The circuit of Figure 16 drives a program-
mable current IL into a load referenced to a negative supply.
Figure 17 shows the circuit for sinking a programmable current,
IL. The same set of circuit equations apply for both diagrams.
IL = I3 = I2 + I1
I1 =
D
×|V
IN |
R
DAC
,
D
= 0 to
4095
4096
I2 =
1
R1
D
×|V
IN |
R
DAC
RFB =
D
×|V
IN |
R1
, since RFB = RDAC
IL =
D
×|V
IN |
R1
+
D
×|V
IN |
R
DAC
=
D
×|V
IN |
R1
× 1 +
R1
R
DAC
Note that by making R1 much smaller than RDAC, the circuit
becomes insensitive to both the absolute value of RDAC and its
temperature variations. Now, the only resistor determining load
current IL is the sense resistor R1.
If R1 = 100
, then the programming range is 0 mA to 100 mA,
and the resolution is 0.024 mA.
Figure 16. Programmable Current Source
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相关代理商/技术参数 |
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| AD7845JN | 制造商:Analog Devices 功能描述:SEMICONDUCTORSLINEAR |
| AD7845JNZ | 功能描述:IC DAC 12BIT MULT LC2MOS 24-DIP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 设置时间:4µs 位数:12 数据接口:串行 转换器数目:2 电压电源:单电源 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:8-TSSOP，8-MSOP（0.118"，3.00mm 宽） 供应商设备封装:8-uMAX 包装:管件 输出数目和类型:2 电压，单极 采样率（每秒）:* 产品目录页面:1398 (CN2011-ZH PDF) |
| AD7845JP | 功能描述:IC DAC 12BIT MULT LC2MOS 28-PLCC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:- 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）:* |
| AD7845JP-REEL | 功能描述:Bit Digital to Analog Converter 28-PLCC (11.51x11.51) 制造商:analog devices inc. 系列:* 包装:带卷（TR） 零件状态:上次购买时间 位数:* 数模转换器数:* 建立时间:* 输出类型:* 差分输出:* 数据接口:* 参考类型:* 电压 - 电源，模拟:* 电压 - 电源，数字:* INL/DNL（LSB）:* 架构:* 工作温度:* 封装/外壳:28-LCC（J 形引线） 供应商器件封装:28-PLCC（11.51x11.51） 标准包装:1 |
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