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參數(shù)資料
| 型號： | SP9840BS |
| 英文描述： | 8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| 中文描述： | 8位八路，4象限乘法，BiCMOS工藝援 |
| 文件頁數(shù)： | 7/10頁 |
| 文件大?。?/td> | 134K |
| 代理商： | SP9840BS |
263
a)
b)
Figure 2. a) Inverted Single–Quadrant Operation; b) 4–Quadrant Operation
Applications which require two–quadrant operation
with respect to pseudoground should use the
SIPEX
SP9841
or
SP9842
two–quadrant multiplying DACs.
The choice of voltage to use for the pseudoground is
limited by the legal voltage swing at the op amp output.
The op amp exhibits excellent linearity for output
voltages between, conservatively, 100mV and V
–
1.5V. The op amp BiCMOS output stage consists of
an npn follower loaded by an NMOS common sourced
to ground. This circuit exhibits wide bandwidth and
can source large currents, while retaining the capabil-
ity of driving the output to voltages close to ground.
At output voltages below 25mV, feedback forces
some op amp internal nodes toward the supply
rails. The NMOS pull–down device gets driven
hard and the NMOS device enters the linear
region — it begins to function in the same
manner as a 50 ohm resistor. In reality, the
wideband amplifier output stage sinks some
internal quiescent current even when driving the
output towards ground. This sunk current drops
across the output stage NMOS transistor ON–
resistance and internal routing resistance to pro-
vide a minimum output voltage below which the
amplifier cannot drive. This minimum voltage
is in the 15 to 25mV range. It varies within a
package with each op amp's offset voltage and
biasing variations. If an input voltage lower than
this minimum, such as code 255 when V
(X) is
grounded, is requested, feedback within the op
amp circuit will force internal nodes to the rails,
while the output will remain saturated near this
minimum value. Non–saturated monotonic be-
havior returns between 25mV and 100mV at the
output, but full open loop gain and linearity are
not apparent until the output voltage is nearly
100mV above the negative supply. Four–quad-
rant (programmable signed attenuator) applica-
tions usually bias V
up at system
pseudoground, well above this saturation re-
gion, and therefore maintain linearity even at
high attenuations (i.e. near code 80
HEX
).
Driving the Reference Inputs
The eight independent V
inputs of the
SP9840
, and
the four–pair of inputs in the
SP9843
, exhibit a code–
dependent input resistance, as shown in the specifica-
tions, and as a typical graph. In general, these inputs
should be driven by an amplifier capable of handling
Table 2. Logic Control Input Truth Table.
SDI
X
CLK
L
LOADH
L
PRESETL
H
LOGIC OPERATION
No Change
Data
L
H
Shift In One Bit from SDI
Shift Out 12–clock delayed data at SDO
X
X
X
L
All DAC Registers Preset to 80
H
(Note 1)
Load Serial Register Data into DAC(X) Register
X
L
H
H
Note 1: "Preset" may not persist at all DACs if LOADH is high when PRESETL returns high.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP9840KN | 8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| SP9840KS | 8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| SP9843 | 8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| SP9843BS | 8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| SP9843KS | 8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP9840KN | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| SP9840KS | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:8-Bit Octal, 4-Quadrant Multiplying, BiCMOS DAC |
| SP9841 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:8-Bit Octal, 2-Quadrant Multiplying, BiCMOS DAC |
| SP9841BN | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:8-Bit Octal, 2-Quadrant Multiplying, BiCMOS DAC |
| SP9841BS | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:8-Bit Octal, 2-Quadrant Multiplying, BiCMOS DAC |
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