參數(shù)資料
型號(hào)： AD7908
廠商： Analog Devices, Inc.
英文描述： 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP
中文描述： 8通道，1 MSPS的，8-/10-/12-Bit與序列ADC的20引腳TSSOP封裝
文件頁(yè)數(shù)： 16/24頁(yè)
文件大?。?/td> 607K
代理商： AD7908
AD7908/AD7918/AD7928
REV. A
POWER-ON
DUMMY CONVERSION
DIN = ALL 1s
DIN: WRITE TO CONTROL REGISTER,
WRITE BIT = 1,
SELECT CODING, RANGE, AND POWER MODE.
SELECT CHANNEL A2–A0 FOR CONVERSION.
SEQ = 1 SHADOW = 1
DOUT: CONVERSION RESULT FROM CHANNEL 0
CONTINUOUSLY CONVERTS ON A CONSECUTIVE
SEQUENCE OF CHANNELS FROM CHANNEL 0 UP
TO AND INCLUDING THE PREVIOUSLY SELECTED
A2–A0 IN THE CONTROL REGISTER
WRITE BIT = 0
CONTINUOUSLY CONVERTS ON THE SELECTED
SEQUENCE OF CHANNELS BUT WILL ALLOW
RANGE, CODING, AND SO ON, TO CHANGE IN THE
CONTROL REGISTER WITHOUT INTERRUPTING
THE SEQUENCE, PROVIDED SEQ = 1
SHADOW = 0
WRITE BIT = 1,
SEQ = 1,
SHADOW = 0
CS
CS
CS
Figure 4. SEQ Bit = 1, SHADOW Bit = 1 Flowchart
CIRCUIT INFORMATION
The AD7908/AD7918/AD7928 are high speed, 8-channel, 8-bit,
10-bit, and 12-bit, single supply, A/D converters, respectively.
The parts can be operated from a 2.7 V to 5.25 V supply. When
operated from either a 5 V or 3 V supply, the AD7908/AD7918/
AD7928 are capable of throughput rates of 1 MSPS when provided
with a 20 MHz clock.
The AD7908/AD7918/AD7928 provide the user with an on-chip
track-and-hold, A/D converter, and a serial interface housed in
a 20-lead TSSOP package. The AD7908/AD7918/AD7928 each
have eight single-ended input channels with a channel sequencer,
allowing the user to select a channel sequence through which the
ADC can cycle with each consecutive
CS
falling edge. The serial
clock input accesses data from the part, controls the transfer of
data written to the ADC, and provides the clock source for the
successive approximation A/D converter. The analog input
range for the AD7908/AD7918/AD7928 is 0 V to REF
IN
or 0 V
to 2 REF
IN
, depending on the status of Bit 1 in the Control
Register. For the 0 to 2 REF
IN
range, the part must be oper-
ated from a 4.75 V to 5.25 V supply.
The AD7908/AD7918/AD7928 provide flexible power management
options to allow the user to achieve the best power performance
for a given throughput rate. These options are selected by pro-
gramming the power management bits, PM1 and PM0, in the
Control Register.
CONVERTER OPERATION
The AD7908/AD7918/AD7928 are 8-, 10-, and 12-bit succes-
sive approximation analog-to-digital converters based around a
capacitive DAC, respectively. The AD7908/AD7918/AD7928
can convert analog input signals in the range 0 V to REF
IN
or 0 V
to 2 REF
IN
. Figures 5 and 6 show simplified schematics of
the ADC. The ADC is comprised of control logic, SAR, and
a capacitive DAC, which are used to add and subtract fixed
amounts of charge from the sampling capacitor to bring the
comparator back into a balanced condition. Figure 5 shows the
ADC during its acquisition phase. SW2 is closed and SW1 is in
position A. The comparator is held in a balanced condition and
the sampling capacitor acquires the signal on the selected V
IN
channel.
V
IN
0
V
IN
7
AGND
A
B
SW1
SW2
COMPARATOR
CONTROL
LOGIC
CAPACITIVE
DAC
4k
Figure 5. ADC Acquisition Phase
When the ADC starts a conversion (see Figure 6), SW2 will
open and SW1 will move to position B, causing the comparator
to become unbalanced. The Control Logic and the Capacitive
DAC are used to add and subtract fixed amounts of charge from
the sampling capacitor to bring the comparator back into a
balanced condition. When the comparator is rebalanced, the
conversion is complete. The Control Logic generates the ADC
output code. Figures 8 and 9 show the ADC transfer functions.
V
IN
0
.
.
V
IN
7
AGND
A
B
SW1
SW2
COMPARATOR
CONTROL
LOGIC
4k
CAPACITIVE
DAC
Figure 6. ADC Conversion Phase
Analog Input
Figure 7 shows an equivalent circuit of the analog input structure
of the AD7908/AD7918/AD7928. The two diodes D1 and D2
provide ESD protection for the analog inputs. Care must be taken
to ensure that the analog input signal never exceeds the supply
rails by more than 300 mV. This will cause these diodes to
become forward biased and start conducting current into the
substrate. 10 mA is the maximum current these diodes can conduct
without causing irreversible damage to the part. The capacitor
C1 in Figure 7 is typically about 4 pF and can primarily be attrib-
uted to pin capacitance. The resistor R1 is a lumped component
made up of the on resistance of the track-and-hold switch and
also includes the on resistance of the input multiplexer. The
total resistance is typically about 400
ADC sampling capacitor and has a capacitance of 30 pF typically.
For ac applications, removing high frequency components from
the analog input signal is recommended by use of an RC low-
pass filter on the relevant analog input pin. In applications where
harmonic distortion and signal-to-noise ratio are critical, the analog
input should be driven from a low impedance source. Large
source impedances will significantly affect the ac performance of
the ADC. This may necessitate the use of an input buffer ampli-
fier. The choice of the op amp will be a function of the particular
application.
. The capacitor C2 is the
–16–
相關(guān)PDF資料
PDF描述
AD7908BRU 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP
AD7908BRU-REEL 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP
AD7908BRU-REEL7 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP
AD7918 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP
AD7918BRU 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD7908BRU 制造商:Analog Devices 功能描述:ADC Single SAR 1Msps 8-bit Serial 20-Pin TSSOP 制造商:Rochester Electronics LLC 功能描述:8-BIT 8, CH 1 MSPS ADC - Bulk 制造商:Analog Devices 功能描述:IC 8BIT ADC SMD 7908 TSSOP20
AD7908BRU-REEL 制造商:Analog Devices 功能描述:ADC Single SAR 1Msps 8-bit Serial 20-Pin TSSOP T/R 制造商:Analog Devices 功能描述:ADC SGL SAR 1MSPS 8BIT SERL 20TSSOP - Tape and Reel
AD7908BRU-REEL7 制造商:Analog Devices 功能描述:ADC Single SAR 1Msps 8-bit Serial 20-Pin TSSOP T/R 制造商:Analog Devices 功能描述:ADC SGL SAR 1MSPS 8BIT SERL 20TSSOP - Tape and Reel
AD7908BRUZ 功能描述:IC ADC 8BIT 8CH 1MSPS 20-TSSOP RoHS:是 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:microPOWER™ 位數(shù):8 采樣率（每秒）:1M 數(shù)據(jù)接口:串行，SPI? 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:- 電壓電源:模擬和數(shù)字 工作溫度:-40°C ~ 125°C 安裝類(lèi)型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:24-VQFN 裸露焊盤(pán)（4x4） 包裝:Digi-Reel® 輸入數(shù)目和類(lèi)型:8 個(gè)單端，單極 產(chǎn)品目錄頁(yè)面:892 (CN2011-ZH PDF) 其它名稱(chēng):296-25851-6
AD7908BRUZ 制造商:Analog Devices 功能描述:IC 8BIT ADC SMD 7908 TSSOP20
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*