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參數(shù)資料
| 型號： | AD7245A |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | LC2MOS 12-Bit DACPORTs |
| 中文描述： | LC2MOS 12位DACPORTs |
| 文件頁數(shù)： | 8/16頁 |
| 文件大?。?/td> | 306K |
| 代理商： | AD7245A |
AD7245A/AD7248A
CIRCUIT INFORMAT ION
REV. A
–8–
D/A SE CT ION
T he AD7245A/AD7248A contains a 12-bit voltage mode digi-
tal-to-analog converter. T he output voltage from the converter
has the same positive polarity as the reference voltage allowing
single supply operation. T he reference voltage for the DAC is
provided by an on-chip buried Zener diode.
T he DAC consists of a highly stable, thin-film, R–2R ladder and
twelve high-speed NMOS single-pole, double-throw switches.
T he simplified circuit diagram for this DAC is shown in Figure 1.
Figure 1. D/A Simplified Circuit Diagram
T he input impedance of the DAC is code dependent and can
vary from 8 k
to infinity. T he input capacitance also varies
with code, typically from 50 pF to 200 pF.
OP AMP SE CT ION
T he output of the voltage mode D/A converter is buffered by a
noninverting CMOS amplifier. T he user has access to two gain
setting resistors which can be connected to allow different out-
put voltage ranges (discussed later). T he buffer amplifier is ca-
pable of developing up to 10 V across a 2 k
load to GND.
T he output amplifier can be operated from a single positive
power supply by tying V
SS
= AGND = 0 V. T he amplifier can
also be operated from dual supplies to allow a bipolar output
range of –5 V to +5 V. T he advantages of having dual supplies
for the unipolar output ranges are faster settling time to voltages
near 0 V, full sink capability of 2.5 mA maintained over the en-
tire output range and elimination of the effects of negative offset
on the transfer characteristic (outlined previously). Figure 2
shows the sink capability of the amplifier for single supply
operation.
Figure 2. Typical Single Supply Sink Current vs.
Output Voltage
T he small signal (200 mV p-p) bandwidth of the output buffer
amplifier is typically 1 MHz. T he output noise from the ampli-
fier is low with a figure of 25 nV/
√
Hz
at a frequency of 1 kHz.
T he broadband noise from the amplifier has a typical peak-to-
peak figure of 150
μ
V for a 1 MHz output bandwidth. T here is
no significant difference in the output noise between single and
dual supply operation.
VOLT AGE RE FE RE NCE
T he AD7245A/AD7248A contains an internal low noise buried
Zener diode reference which is trimmed for absolute accuracy
and temperature coefficient. T he reference is internally con-
nected to the DAC. Since the DAC has a variable input imped-
ance at its reference input the Zener diode reference is buffered.
T his buffered reference is available to the user to drive the cir-
cuitry required for bipolar output ranges. It can be used as a ref-
erence for other parts in the system provided it is externally
buffered. T he reference will give long-term stability comparable
with the best discrete Zener reference diodes. T he performance
of the AD7245A/AD7248A is specified with internal reference,
and all the testing and trimming is done with this reference. T he
reference should be decoupled at the REF OUT pin and recom-
mended decoupling components are 10
μ
F and 0.1
μ
F capaci-
tors in series with a 10
resistor. A simplified schematic of the
reference circuitry is shown in Figure 3.
Figure 3. Internal Reference
DIGIT AL SE CT ION
T he AD7245A/AD7248A digital inputs are compatible with ei-
ther T T L or 5 V CMOS levels. All data inputs are static pro-
tected MOS gates with typical input currents of less than 1 nA.
T he control inputs sink higher currents (150
μ
A max) as a result
of the fast digital interfacing. Internal input protection of all
logic inputs is achieved by on-chip distributed diodes.
T he AD7245A/AD7248A features a very low digital feedthrough
figure of 10 nV-s in a 5 V output range. T his is due to the volt-
age mode configuration of the DAC. Most of the impulse is ac-
tually as a result of feedthrough across the package.
INT E RFACE LOGIC INFORMAT ION—AD7245A
T able I shows the truth table for AD7245A operation. T he part
contains two 12-bit latches, an input latch and a DAC latch.
CS
and
WR
control the loading of the input latch while
LDAC
con-
trols the transfer of information from the input latch to the
DAC latch. All control signals are level triggered; and therefore,
either or both latches may be made transparent, the input latch
by keeping
CS
and
WR
“LOW”, the DAC latch by keeping
LDAC
“LOW.” Input data is latched on the rising edge of
WR
.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD7245AAN | POLARIZED CAPACITOR (RADIAL) |
| AD7245AAP | LC2MOS 12-Bit DACPORTs |
| AD7245AAQ | LC2MOS 12-Bit DACPORTs |
| AD7245AAR | LC2MOS 12-Bit DACPORTs |
| AD7245ABN | LC2MOS 12-Bit DACPORTs |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7245AAN | 功能描述:IC DAC 12BIT LC2MOS 24-DIP RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:DACPORT® 產(chǎn)品培訓模塊:Data Converter Fundamentals DAC Architectures 標準包裝:750 系列:- 設(shè)置時間: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 |
| AD7245AANZ | 功能描述:IC DAC 12BIT LC2MOS 24-DIP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:DACPORT® 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 設(shè)置時間:4µs 位數(shù):12 數(shù)據(jù)接口:串行 轉(zhuǎn)換器數(shù)目:2 電壓電源:單電源 功率耗散（最大）:- 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:8-uMAX 包裝:管件 輸出數(shù)目和類型:2 電壓，單極 采樣率（每秒）:* 產(chǎn)品目錄頁面:1398 (CN2011-ZH PDF) |
| AD7245AANZ | 制造商:Analog Devices 功能描述:IC 12-BIT DAC |
| AD7245AAP | 功能描述:IC DAC 12BIT W/REF 28-PLCC RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:DACPORT® 產(chǎn)品培訓模塊:Data Converter Fundamentals DAC Architectures 標準包裝:750 系列:- 設(shè)置時間: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 |
| AD7245AAP-REEL | 制造商:Analog Devices 功能描述:DAC 1-CH R-2R 12-bit 28-Pin PLCC T/R 制造商:Rochester Electronics LLC 功能描述:PARALLEL,12-BIT DACPORT - Tape and Reel |
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