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參數(shù)資料
| 型號： | DAC7821IRGPR |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | 50/MDR/WMNT/PLASTIC PLUG/20MIN |
| 中文描述： | 12位，并行輸入，乘法數(shù)字到模擬轉(zhuǎn)換器 |
| 文件頁數(shù)： | 13/18頁 |
| 文件大小： | 1597K |
| 代理商： | DAC7821IRGPR |
www.ti.com
+2.5V
(+10V)
U4
OPA277
10k
W
10k
W
5k
W
-
￡
2.5V
￡
+2.5V
V
OUT
( 10V
-
￡
￡
+10V)
V
OUT
U2
GND
I
1
OUT
R
FB
V
REF
V
DD
V
DD
V
OUT
I
2
OUT
C
1
OPA277
DAC7821
C
2
Programmable Current Source Circuit
A DAC7821 can be integrated into the circuit in
Figure 30
to implement an improved Howland current pump for
precise voltage-to-current conversions. Bidirectional current flow and high voltage compliance are two features of
the circuit. With a matched resistor network, the load current of the circuit is shown by
Equation 3
:
I
L
R2
R3
R3
R1
V
REF
D
(3)
Z
O
R1 R3 R1
R3
R2
R1 R2
R1 R2
R3
(4)
R2
￠
15k
W
I
L
LOAD
C
1
10pF
U3
OPA277
R1
￠
150k
W
R3
￠
50
W
R3
50
W
R1
150k
W
R2
15k
W
OPA277
DAC7821
GND
I
1
OUT
R
FB
V
REF
V
DD
V
DD
V
OUT
I
2
OUT
U1
U2
DAC7821
SBAS365A–OCTOBER 2005–REVISED FEBRUARY 2006
APPLICATION INFORMATION (continued)
External resistance mismatching is the significant error in
Figure 29
.
Figure 29. Bipolar Output Circuit
The value of R3 in the previous equation can be reduced to increase the output current drive of U3. U3 can drive
±
20 mA in both directions with voltage compliance limited up to 15 V by the U3 voltage supply. Elimination of the
circuit compensation capacitor C
1
in the circuit is not suggested as a result of the change in the output
impedance Z
O
, according to
Equation 4
:
As shown in
Equation 4
, with matched resistors, Z
O
is infinite and the circuit is optimum for use as a current
source. However, if unmatched resistors are used, Z
O
is positive or negative with negative output impedance
being a potential cause of oscillation. Therefore, by incorporating C
1
into the circuit, possible oscillation problems
are eliminated. The value of C
1
can be determined for critical applications; for most applications, however, a
value of several pF is suggested.
Figure 30. Programmable Bidirectional Current Source Circuit
13
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| DAC7822IRTAR | 功能描述:數(shù)模轉(zhuǎn)換器- DAC 12-bit Dual Channel Par Input Mult 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)定時間:1 us 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| DAC7822IRTARG4 | 功能描述:數(shù)模轉(zhuǎn)換器- DAC 12-bit Dual Channel Par Input Mult 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)定時間:1 us 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| DAC7822IRTAT | 功能描述:數(shù)模轉(zhuǎn)換器- DAC 12-bit Dual Channel Par Input Mult 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)定時間:1 us 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
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