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| 型號： | AD7938BCPZ-6 |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 14/32頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC ADC 12BIT 8CH 625KSPS 32LFCSP |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 位數(shù)： | 12 |
| 采樣率（每秒）： | 625k |
| 數(shù)據(jù)接口： | 并聯(lián) |
| 轉(zhuǎn)換器數(shù)目： | 1 |
| 功率耗散（最大）： | 7.5mW |
| 電壓電源： | 單電源 |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 32-VFQFN 裸露焊盤，CSP |
| 供應(yīng)商設(shè)備封裝： | 32-LFCSP-VQ |
| 包裝： | 托盤 |
| 輸入數(shù)目和類型： | 8 個單端，單極；4 個差分，單極；4 個偽差分，單極；7 偽差分，單極 |
| 配用： | EVAL-AD7938CBZ-ND - EVAL BOARD FOR AD7938 |
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Data Sheet
AD7938-6
Rev. C | Page 21 of 32
Using the Sequencer: Programmable Sequence
(SEQ = 0, SHDW = 1 )
The AD7938-6 can be configured to automatically cycle through a
number of selected channels using the on-chip programmable
sequencer by setting SEQ = 0 and SHDW = 1 in the control
register. The analog input channels to be converted are selected
by setting the relevant bits in the shadow register to 1 (see
Table 11).
Once the shadow register has been programmed with the required
sequence, the next conversion executed is on the lowest channel
programmed in the SHDW register. The next conversion
executed is on the next highest channel in the sequence, and so
on. When the last channel in the sequence is converted, the
internal multiplexer returns to the first channel selected in the
shadow register and commences the sequence again.
It is not necessary to write to the control register again once a
sequencer operation has been initiated. The WR input must be
kept high to ensure that the control register is not accidentally
overwritten or that a sequence operation is not interrupted.
If the control register is written to at any time during the
sequence, ensure that the SEQ and SHDW bits are set
to 1, 0 to avoid interrupting the conversion sequence. The
sequence program remains in force until such time as the
AD7938-6 is written to and the SEQ and SHDW bits are
configured with any bit combination except 1, 0.
shows a flow chart of the programmable sequence operation.
POWER ON
WRITE TO THE CONTROL REGISTER TO
SET UP OPERATING MODE, ANALOG INPUT
AND OUTPUT CONFIGURATION
SET SEQ = 0 SHDW = 1.
INITIATE A WRITE CYCLE.
THIS WRITE CYCLE IS TO PROGRAM THE SHADOW REGISTER.
SET RELEVANT BITS TO SELECT
THE CHANNELS TO BE INCLUDED IN THE SEQUENCE.
SEQ BIT = 1
SHDW BIT = 0
CONTINUOUSLY CONVERT
CONSECUTIVE
CHANNELS SELECTED
WITH EACH CONVST PULSE
BUT ALLOWS THE RANGE,
CONTINUOUSLY CONVERT
CONSECUTIVE
CHANNELS SELECTED
IN THE SHADOW REGISTER
WITH EACH CONVST PULSE.
CODING, ANALOG INPUT TYPE,
ETC BITS IN THE CONTROL
REGISTER TO BE CHANGED
WITHOUT INTERRUPTING
THE SEQUENCE.
04
75
1-
0
39
WR = HIGH
SEQ BIT = 0
SHDW BIT = 1
Figure 31. Programmable Sequence Flow Chart
Consecutive Sequence (SEQ = 1, SHDW = 1)
A sequence of consecutive channels can be converted beginning
with Channel 0 and ending with a final channel selected by
writing to the ADD2 to ADD0 bits in the control register.
This is done by setting the SEQ and SHDW bits in the control
register to 1. In this mode, the sequencer can be used without
having to write to the shadow register. In this mode, once the
control register is written to, the next conversion is on Channel
0, then Channel 1, and so on until the channel selected by the
address bits (ADD2 to ADD0) is reached. The cycle begins
again provided the WR input is tied high. If low, the SEQ and
SHDW bits must be set to 1, 0 to allow the ADC to continue its
preprogrammed sequence uninterrupted.
shows the
flow chart of the consecutive sequence mode.
POWER ON
WRITE TO THE CONTROL REGISTER TO
SET UP OPERATING MODE, ANALOG INPUT
AND OUTPUT CONFIGURATION SELECT
FINAL CHANNEL (ADD2 TO ADD0) IN
CONSECUTIVE SEQUENCE.
SET SEQ = 1 SHDW = 1.
CONTINUOUSLY CONVERT A CONSECUTIVE
SEQUENCE OF CHANNELS FROM CHANNEL 0
UP TO AND INCLUDING THE PREVIOUSLY
SELECTED FINAL CHANNEL ON ADD2 TO ADD0
WITH EACH CONVST PULSE.
SEQ BIT = 1
SHDW BIT = 0
CONTINUOUSLY CONVERT
CONSECUTIVE CHANNELS SELECTED
WITH EACH CONVST PULSE BUT
ALLOWS THE RANGE, CODING, ANALOG
INPUT TYPE, ETC BITS IN THE
CONTROL REGISTER TO BE CHANGED
WITHOUT INTERRUPTING
THE SEQUENCE.
04
75
1
-0
4
0
Figure 32. Consecutive Sequence Mode Flow Chart
REFERENCE
The AD7938-6 can operate with either the on-chip reference or
external reference. The internal reference is selected by setting
the REF bit in the internal control register to 1. A block diagram
of the internal reference circuitry is shown in Figure 33. The
internal reference circuitry includes an on-chip 2.5 V band gap
reference and a reference buffer. When using the internal
reference, the VREFIN/VREFOUT pin should be decoupled to AGND
with a 0.47 μF capacitor. This internal reference not only
provides the reference for the analog-to-digital conversion, but
it can also be used externally in the system. It is recommended
that the reference output be buffered using an external precision
op amp before applying it anywhere in the system.
REFERENCE
AD7938-6
ADC
BUFFER
0
475
1-
0
41
VREFIN/
VREFOUT
Figure 33. Internal Reference Circuit Block Diagram
Alternatively, an external reference can be applied to the
VREFIN/VREFOUT pin of the AD7938-6. An external reference input
is selected by setting the REF bit in the internal control register
to 0. The external reference input range is 0.1 V to VDD. It is
important to ensure that, when choosing the reference value,
the maximum analog input range (VIN MAX) is never greater than
VDD + 0.3 V to comply with the maximum ratings of the device.
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| AD7938BCPZ-6REEL7 | 功能描述:IC ADC 12BIT 8CH 625KSPS 32LFCSP RoHS:是 類別: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:1,000 系列:- 位數(shù):16 采樣率（每秒）:45k 數(shù)據(jù)接口:串行 轉(zhuǎn)換器數(shù)目:2 功率耗散（最大）:315mW 電壓電源:模擬和數(shù)字 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:28-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:28-SOIC W 包裝:帶卷 (TR) 輸入數(shù)目和類型:2 個單端，單極 |
| AD7938BCPZ-REEL7 | 功能描述:IC ADC 12BIT 8CH 1.5MSPS 32LFCSP RoHS:是 類別: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:1,000 系列:- 位數(shù):12 采樣率（每秒）:300k 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:75mW 電壓電源:單電源 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:24-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:24-SOIC 包裝:帶卷 (TR) 輸入數(shù)目和類型:1 個單端，單極；1 個單端，雙極 |
| AD7938BSU | 制造商:Analog Devices 功能描述: |
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| AD7938BSU-6REEL | 制造商:AD 制造商全稱:Analog Devices 功能描述:8-Channel, 625 kSPS, 12-Bit Parallel ADCs with a Sequencer |
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