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參數資料
| 型號： | AD7904 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | ADC |
| 英文描述： | 4-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 16-Lead TSSOP |
| 中文描述： | 4通道，1 MSPS的，8-/10-/12-Bit ADC的16與序列鉛TSSOP封裝 |
| 文件頁數： | 18/24頁 |
| 文件大小： | 411K |
| 代理商： | AD7904 |
–18–
AD7904/AD7914/AD7924
REV. 0
better dynamic performance with a V
DD
of 5 V while still being
able to interface to 3 V processors. Care should be taken to
ensure V
DRIVE
does not exceed V
DD
by more than 0.3 V. (See
the Absolute Maximum Ratings section).
Reference
An external reference source should be used to supply the 2.5 V
reference to the AD7904/AD7914/AD7924. Errors in the refer-
ence source will result in gain errors in the AD7904/AD7914/
AD7924 transfer function and will add to the specified full-scale
errors of the part. A capacitor of at least 0.1
μ
F should be placed
on the REF
IN
pin. Suitable reference sources for the AD7904/
AD7914/AD7924 include the AD780, REF 193, and the AD1582.
If 2.5 V is applied to the REF
IN
pin, the analog input range can
either be 0 V to 2.5 V or 0 V to 5 V, depending on the setting of
the RANGE bit in the Control Register.
MODES OF OPERATION
The AD7904/AD7914/AD7924 have a number of different
modes of operation. These modes are designed to provide flex-
ible power management options. These options can be chosen
to optimize the power dissipation/throughput rate ratio for dif-
fering application requirements. The mode of operation of the
AD7904/AD7914/AD7924 is controlled by the power manage-
ment bits, PM1 and PM0, in the Control Register, as detailed in
Table III. When power supplies are first applied to the AD7904/
AD7914/AD7924, care should be taken to ensure that the part
is placed in the required mode of operation (see the Powering
Up the AD7904/AD7914/AD7924 section).
Normal Mode (PM1 = PM0 = 1)
This mode is intended for the fastest throughput rate performance
as the user does not have to worry about any power-up times
with the AD7904/AD7914/AD7924 remaining fully powered at
all times. Figure 11 shows the general diagram of the operation
of the AD7904/AD7914/AD7924 in this mode.
The conversion is initiated on the falling edge of
CS
and the track
and hold will enter hold mode as described in the Serial Interface
section. The data presented to the AD7904/AD7914/AD7924 on
the DIN line during the first 12 clock cycles of the data transfer
are loaded into the Control Register (provided WRITE bit is set
to 1). The part will remain fully powered up in normal mode at
the end of the conversion as long as PM1 and PM0 are set to 1
in the write transfer during that same conversion. To ensure
continued operation in Normal Mode, PM1 and PM0 must both
be loaded with 1 on every data transfer, assuming a write opera-
tion is taking place. If the WRITE bit is set to 0, then the power
management bits will be left unchanged and the part will remain
in Normal Mode.
Sixteen serial clock cycles are required to complete the conver-
sion and access the conversion result. The track and hold will go
back into track on the fourteenth SCLK falling edge.
CS
may
then idle high until the next conversion or may idle low until
sometime prior to the next conversion, (effectively idling
CS
low).
Once a data transfer is complete (DOUT has returned to three-
state), another conversion can be initiated after the quiet time,
t
QUIET
,
has elapsed by bringing
CS
low again.
1
12
CS
SCLK
DOUT
DIN
16
2 LEADING Z+ CONVERSION RESULT
DATA IN TO CONTROL REGISTER
NOTE: CONTROL REGISTER DATA IS LOADED ON FIRST 12 SCLK CYCLES
Figure 11. Normal Mode Operation
Full Shutdown (PM1 = 1, PM0 = 0)
In this mode, all internal circuitry on the AD7904/AD7914/
AD7924 is powered down. The part retains information in the
Control Register during full shutdown. The AD7904/AD7914/
AD7924 remains in full shutdown until the power management
bits in the Control Register, PM1 and PM0, are changed.
If a write to the Control Register occurs while the part is in Full
Shutdown, with the power management bits changed to PM0 =
PM1 = 1, Normal mode, the part will begin to power up on the
CS
rising edge. The track and hold that was in hold while the
part was in Full Shutdown will return to track on the fourteenth
SCLK falling edge.
To ensure that the part is fully powered up, t
POWER UP
(t
12
) should
have elapsed before the next
CS
falling edge. Figure 12 shows
the general diagram for this sequence.
Auto Shutdown (PM1 = 0, PM0 = 1)
In this mode, the AD7904/AD7914/AD7924 automatically enters
shutdown at the end of each conversion when the control register
is updated. When the part is in shutdown, the track and hold is in
hold mode. Figure 13 shows the general diagram of the operation
of the AD7904/AD7914/AD7924 in this mode. In shutdown mode
all internal circuitry on the AD7904/AD7914/AD7924 is
powered down. The part retains information in the Control
Register during shutdown. The AD7904/AD7914/AD7924
remains in shutdown until the next
CS
falling edge it receives.
On this
CS
falling edge
the track and hold that was in hold while
the part was in shutdown
will return to track. Wake-up time
from auto shutdown is 1
μ
s maximum, and the user should
ensure that 1
μ
s has elapsed before attempting a valid conver-
sion. When running the AD7904/AD7914/AD7924 with
a
20 MHz clock, one 16 SCLK dummy cycle should be sufficient
to ensure the part is fully powered up. During this dummy cycle
the contents of the Control Register should remain unchanged,
therefore the WRITE bit should be 0 on the DIN line. This
dummy cycle effectively halves the throughput rate of the part,
with every other conversion result being valid. In this mode the
power consumption of the part is greatly reduced with the part
entering shutdown at the end of each conversion. When the
Control Register is programmed to move into auto shutdown, it
does so at the end of the conversion. The user can move the ADC
in and out of the low power state by controlling the
CS
signal.
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| AD7904BRU | 功能描述:IC ADC 8BIT 4CH 1MSPS 16-TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 標準包裝:2,500 系列:- 位數:16 采樣率（每秒）:15 數據接口:MICROWIRE?，串行，SPI? 轉換器數目:1 功率耗散（最大）:480µW 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:38-WFQFN 裸露焊盤 供應商設備封裝:38-QFN（5x7） 包裝:帶卷 (TR) 輸入數目和類型:16 個單端，雙極；8 個差分，雙極 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494 |
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| AD7904BRU-REEL7 | 制造商:Analog Devices 功能描述:ADC Single SAR 1Msps 8-bit Serial 16-Pin TSSOP T/R |
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| AD7904BRUZ | 制造商:Analog Devices 功能描述:IC 8BIT ADC SMD 7904 TSSOP16 |
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