參數(shù)資料
型號: AD974ARS
廠商: ANALOG DEVICES INC
元件分類: 通信及網(wǎng)絡(luò)
英文描述: 4-Channel, 16-Bit, 200 kSPS Data Acquisition System
中文描述: SPECIALTY TELECOM CIRCUIT, PDSO28
封裝: SSOP-28
文件頁數(shù): 7/20頁
文件大小: 202K
代理商: AD974ARS
REV. A
AD974
–7–
CONVERSION CONTROL
The AD974 is controlled by two signals: R/
C
and
CS
. When
R/
C
is brought low, with
CS
low, for a minimum of 50 ns, the
input signal will be held on the internal capacitor array and a
conversion “n” will begin. Once the conversion process does
begin, the
BUSY
signal will go low until the conversion is com-
plete. Internally, the signals R/
C
and
CS
are ORed together and
there is no requirement on which signal is taken low first when
initiating a conversion. The only requirement is that there be at
least 10 ns of delay between the two signals being taken low.
After the conversion is complete, the
BUSY
signal will return
high and the AD974 will again resume tracking the input signal.
Under certain conditions the
CS
pin can be tied Low and R/
C
will be used to determine whether you are initiating a conver-
sion or reading data. On the first conversion, after the AD974 is
powered up, the DATA output will be indeterminate.
Conversion results can be clocked serially, using either an
internal clock generated by the AD974 or an external clock.
The AD974 is configured for the internal data clock mode by
pulling the EXT/
INT
pin low. It is configured for the external
clock mode by pulling the EXT/
INT
pin high.
INTERNAL DATA CLOCK MODE
The AD974 is configured to generate and provide the data clock
when the EXT/
INT
pin is held low. Typically
CS
will be tied
low and R/
C
will be used to initiate a conversion “n.” During
the conversion the AD974 will output 16 bits of data, MSB first,
from conversion “n-1” on the DATA pin. This data will be
synchronized with 16 clock pulses provided on the DATACLK
pin. The output data will be valid on both the rising and falling
edge of the data clock as shown in Figure 3. After the LSB has
been presented, the DATACLK pin will stay low until another
conversion is initiated.
In this mode, the digital input/output pins’ transitions are suit-
ably positioned to minimize degradation on the conversion
result, mainly during the second half of the conversion process.
EXTERNAL DATA CLOCK MODE
The AD974 is configured to accept an externally supplied data
clock when the EXT/
INT
pin is held high. This mode of opera-
tion provides several methods by which conversion results can
be read. The output data from conversion “n-1” can be read
during conversion “n,” or the output data from conversion “n”
CS
, R/
C
BUSY
MODE
ACQUIRE
CONVERT
t
1
CONVERT
ACQUIRE
t
3
t
2
t
5
t
6
t
4
t
7
t
23
t
25
t
24
A0, A1
WR1
,
WR2
Figure 2. Basic Conversion Timing
R/
C
DATACLK
DATA
BUSY
1
MSB
BIT 14
t
8
t
1
t
9
2
3
15
16
t
10
t
11
BIT 13
BIT 1
LSB
t
2
t
6
Figure 3. Serial Data Timing for Reading Previous Conversion Results with Internal Clock
(
CS
and EXT/
INT
Set to Logic Low)
相關(guān)PDF資料
PDF描述
AD974 4-Channel, 16-Bit, 200 kSPS Data Acquisition System
AD974AN 4-Channel, 16-Bit, 200 kSPS Data Acquisition System
AD974AR 4-Channel, 16-Bit, 200 kSPS Data Acquisition System
AD974BN 4-Channel, 16-Bit, 200 kSPS Data Acquisition System
AD974BR 4-Channel, 16-Bit, 200 kSPS Data Acquisition System
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