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參數(shù)資料
| 型號(hào)： | AD8842AR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | DAC |
| 英文描述： | 8-Bit Octal, 4-Quadrant Multiplying, CMOS TrimDAC |
| 中文描述： | OCTAL, SERIAL INPUT LOADING, 5.4 us SETTLING TIME, 8-BIT DAC, PDSO24 |
| 封裝： | 0.300 INCH, SOIC-24 |
| 文件頁(yè)數(shù)： | 9/12頁(yè) |
| 文件大?。?/td> | 506K |
| 代理商： | AD8842AR |
AD8842
REV. 0
–9–
CIRCUIT OPERATION
The AD8842 is a general purpose 8-channel ac or dc signal-
level adjustment device designed to replace potentiometers used
in the three-terminal connection mode. Eight independent
channels of programmable signal level control are available in
this 24-pin package device. The outputs are completely buffered
providing up to 3 mA of output drive-current to drive external
loads. The functional equivalent DAC and amplifier combina-
tion shown in Figure 27 produces four-quadrant multiplication
of the signal inputs applied to V
IN
times the digital input control
word. In addition the AD8842 provides a 50 kHz full power
bandwidth in each four-quadrant multiplying channel. Operat-
ing from plus and minus 5 V power supplies, analog inputs and
outputs of
±
3 V are easily accommodated.
Figure 27. Functional Equivalent Circuit to the AD8842
Results in a 4-Quadrant Multiplying Channel
In order to simplify use with a controlling microprocessor a
PCB space saving three-wire serial data interface was chosen.
This interface can be easily adapted to almost all microcom-
puter and microprocessor systems. A clock (CLK), serial data
input (SDI) and a load (LD) strobe pins make up the three-wire
interface. The 12-bit input data word used to change the value
of the internal DAC registers contains a 4-bit address and 8-bits
of data. Using this word combination any DAC register can be
changed at a given time without disturbing the other channels.
A serial data output SDO pin simplifies cascading multiple
AD8842s without adding address decoder chips to the system.
During system power up a logic low on the preset
PR
pin forces
all DAC registers to 80
H
which in turn forces all the buffer am-
plifier outputs to zero volts. This asynchronous input pin
PR
can be activated at any time to force the DAC registers to the
half-scale code 80
H
. This is generally the most convenient place
to start general purpose adjustment procedures.
Achieving 4-Quadrant Multiplying with a Current Conveyor
Amplifier
The traditional current output CMOS digital-to-analog con-
verter requires two amplifiers to perform the current-to-voltage
translation and the half-scale offset to achieve four-quadrant
multiplying capability. The circuit shown in Figure 28 shows
one such traditional connection.
Figure 28. One Traditional Technique to Achieve Four-
Quadrant Multiplying with a Complementary Current
Output DAC
A single new current conveyor amplifier design emulates ampli-
fiers A1 and A2 shown in Figure 28. Figure 29 shows the con-
nection and equations that define this new circuit that achieves
four-quadrant multiplication with only one amplifier.
Figure 29. Current Conveyor Amplifier
Using the equations given in Figure 29 one can calculate the
final output equation as follows:
V
O
=
–
1–
D
256
V
IN
R
×
R
–
–
D
256
×
V
IN
R
×
R
D
D
2
D
V
IN
+
V
IN
V
IN
D
256
×
V
IN
=
=
V
IN
CURRENT CONVEYOR
AMPLIFIER
I
1
I
2
(1- D)
256
D
256
V
REF
R
REF
R
R
V
= V
IN
(D/128–1)
V
REF
R
V
OUT
X
4
2
0
–4
–2
0
–2
2
4
V
O
–4
V
IN
– Volts
V
OUT
= V
IN
(D/128 – 1), WHERE D = 0 TO 255
D = FFH
D = C0H
D = 80H
D = 40H
D = 00H
AD8842 INPUT-OUTPUT VOLTAGE RANGE
V
DAC
V
OUT
V
IN
R
R
V
DAC
= D/256
×
V
IN
V
OUT
= 2
×
V
DAC
– V
IN
= 2 (D/256)
×
V
IN
– V
IN
= (D/128 – 1)
×
V
IN
R/2
A1
R
A2
R/2
CURRENT OUT
DAC
REF
GND
I
1
I
2
V
IN
V
O
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| AD8842AR-REEL | 功能描述:IC DAC MULT 8BIT OCTAL 24-SOIC RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:TrimDAC® 產(chǎn)品培訓(xùn)模塊:Data Converter Fundamentals DAC Architectures 標(biāo)準(zhǔn)包裝:750 系列:- 設(shè)置時(shí)間:7µs 位數(shù):16 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）:100mW 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:28-LCC（J 形引線） 供應(yīng)商設(shè)備封裝:28-PLCC（11.51x11.51） 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）:143k |
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| AD8883B | 制造商:AD 制造商全稱:Analog Devices 功能描述:60 MHz, 2000 V/us Monolithic Op Amp |
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