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參數(shù)資料
| 型號(hào)： | AD7845KRZ-REEL |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 11/12頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC DAC 12BIT MULT LC2MOS 24-SOIC |
| 產(chǎn)品培訓(xùn)模塊： | Data Converter Fundamentals DAC Architectures |
| 標(biāo)準(zhǔn)包裝： | 1,000 |
| 設(shè)置時(shí)間： | 5µs |
| 位數(shù)： | 12 |
| 數(shù)據(jù)接口： | 并聯(lián) |
| 轉(zhuǎn)換器數(shù)目： | 1 |
| 電壓電源： | 雙 ± |
| 功率耗散（最大）： | 150mW |
| 工作溫度： | 0°C ~ 70°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 24-SOIC（0.295"，7.50mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 24-SOIC W |
| 包裝： | 帶卷 (TR) |
| 輸出數(shù)目和類型： | 1 電壓，單極；1 電壓，雙極 |
| 采樣率（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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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| AD7845SE | 制造商:AD 制造商全稱:Analog Devices 功能描述:LC2MOS Complete 12-Bit Multiplying DAC |
| AD7845SE/883B | 功能描述:數(shù)模轉(zhuǎn)換器- DAC COMPLETE 12 BIT MDAC IC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| AD7845SE883B | 制造商:AD 制造商全稱:Analog Devices 功能描述:LC2MOS Complete 12-Bit Multiplying DAC |
| AD7845SQ | 功能描述:數(shù)模轉(zhuǎn)換器- DAC 12-BIT CMOS DAC IC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| AD7845SQ/883B | 功能描述:數(shù)模轉(zhuǎn)換器- DAC COMPLETE 12 BIT DAC IC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
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