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參數(shù)資料
| 型號： | DAC7802L |
| 英文描述： | Dual Monolithic CMOS 12-Bit Multiplying DIGITAL-TO-ANALOG CONVERTERS |
| 中文描述： | 雙路單片CMOS 12位乘法數(shù)字到模擬轉(zhuǎn)換器 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 180K |
| 代理商： | DAC7802L |
9
DAC7800, 01, 02
DGND should be connected together at one point only,
preferably at the power supply ground point. Separate returns
minimize current flow in low-level signal paths if properly
connected. Output op amp analog common (+ input) should
be connected as near to the AGND pins of the DAC780X as
possible.
WIRING PRECAUTIONS
To minimize AC feedthrough when designing a PC board,
care should be taken to minimize capacitive coupling be-
tween the V
REF
lines and the I
OUT
lines. Similarly, capacitive
coupling between DACs may compromise the channel-to-
channel isolation. Coupling from any of the digital control or
data lines might degrade the glitch and digital crosstalk
performance. Solder the DAC780X directly into the
PC
board without a socket. Sockets add parasitic capacitance
(which can degrade AC performance).
AMPLIFIER OFFSET VOLTAGE
The output amplifier used with the DAC780X should have
low input offset voltage to preserve the transfer function
linearity. The voltage output of the amplifier has an error
component which is the offset voltage of the op amp multi-
plied by the “noise gain” of the circuit. This “noise gain” is
equal to (R
F
/R
O
+ 1) where R
O
is the output impedance of the
D/A I
OUT
terminal and R
F
is the feedback network imped-
ance. The nonlinearity occurs due to the output impedance
varying with code. If the 0 code case is excluded (where R
O
= infinity), the R
O
will vary from R to 3R providing a “noise
gain” variation between 4/3 and 2. In addition, the variation
of R
O
is nonlinear with code, and the largest steps in R
O
occur
at major code transitions where the worst differential
nonlinearity is also likely to be experienced. The nonlinearity
seen at the amplifier output is 2V
OS
– 4V
OS
/3 = 2V
OS
/3.
Thus, to maintain good nonlinearity the op amp offset should
be much less than 1/2LSB.
UNIPOLAR CONFIGURATION
Figure 3 shows DAC780X in a typical unipolar (two-quad-
rant) multiplying configuration. The analog output values
versus digital input code are listed in Table II. The opera-
tional amplifiers used in this circuit can be single amplifiers
such as the OPA602, or a dual amplifier such as the OPA2107.
C1 and C2 provide phase compensation to minimize settling
time and overshoot when using a high speed operational
amplifier.
If an application requires the D/A to have zero gain error, the
circuit shown in Figure 4 may be used. Resistors R2 and R4
induce a positive gain error greater than worst-case initial
negative gain error. Trim resistors R1 and R3 provide a
variable negative gain error and have sufficient trim range to
correct for the worst-case initial positive gain error plus the
error produced by R2 and R4.
BIPOLAR CONFIGURATION
Figure 5 shows the DAC780X in a typical bipolar (four-
quadrant) multiplying configuration. The analog output val-
ues versus digital input code are listed in Table III.
DATA INPUT
ANALOG OUTPUT
MSB
↓
↓
LSB
1111 1111 1111
1000 0000 0000
0000 0000 0001
0000 0000 0000
–V
REF
(4095/4096)
–V
REF
(2048/4096) = –1/2V
REF
–V
(1/4096)
0 Volts
TABLE II. Unipolar Output Code.
The operational amplifiers used in this circuit can be single
amplifiers such as the OPA602, a dual amplifier such as the
OPA2107, or a quad amplifier like the OPA404. C1 and C2
provide phase compensation to minimize settling time and
overshoot when using a high speed operational amplifier.
The bipolar offset resistors R5–R7 and R8–R10 should be
ratio-matched to 0.01% to ensure the specified gain error
performance.
DAC A
I
OUT A
DAC B
AGND A
I
OUT B
R
FB B
R
FB A
C1
10pF
C2
10pF
DAC780X
V
OUT A
V
OUT B
–
+
–
+
A1
A2
DGND
V
REF B
V
REF A
V
DD
+5V
C
D
1μF
A1, A2 OPA602 or 1/2 OPA2107.
DAC7802 has a single analog
common, AGND.
+
AGND B
R
100
3
REF B
R
2
47
R
4
47
DAC A
I
OUT A
DAC B
AGND A
I
OUT B
R
FB B
R
FB A
C1 10pF
C2 10pF
DAC780X
V
OUT A
V
OUT B
–
+
–
+
A1
A2
DGND
V
DD
+5V
C
D
1μF
A1, A2 OPA602 or 1/2 OPA2107.
DAC7802 has a single analog
common, AGND.
+
AGND B
V
IN A
R
100
1
REF A
V
V
IN B
V
FIGURE 4. Unipolar Configuration with Gain Trim.
FIGURE 3. Unipolar Configuration.
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| DAC7802LU | 功能描述:數(shù)模轉(zhuǎn)換器- DAC Dual Monolithic CMOS 12-Bit Multiplying 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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| DAC7802LU/1K | 功能描述:數(shù)模轉(zhuǎn)換器- DAC Dual Monolithic CMOS 12-Bit Multiplying 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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| DAC7802LU/1KG4 | 功能描述:數(shù)模轉(zhuǎn)換器- DAC Dual Monolithic CMOS 12-Bit Multiplying 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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| DAC7802LUG4 | 功能描述:數(shù)模轉(zhuǎn)換器- DAC Dual Monolithic CMOS 12-Bit Multiplying 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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
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