AD7641ACP 데이터 시트보기 (PDF) - Analog Devices
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AD7641ACP Datasheet PDF : 28 Pages
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INTERFACES
DIGITAL INTERFACE
The AD7641 has a versatile digital interface that can be set up
as either a serial or a parallel interface with the host system. The
serial interface is multiplexed on the parallel data bus. The AD7641
digital interface also accommodates 2.5 V, 3.3 V, or 5 V logic
with either OVDD at 2.5 V or 3.3 V. OVDD defines the logic
high output voltage. In most applications, the OVDD supply pin
of the AD7641 is connected to the host system interface 2.5 V
or 3.3 V digital supply. By using the D0/OB/2C input pin, either
twos complement or straight binary coding can be used.
The two signals CS and RD control the interface. When at least
one of these signals is high, the interface outputs are in high
impedance. Usually, CS allows the selection of each AD7641 in
multicircuit applications and is held low in a single AD7641
design. RD is generally used to enable the conversion result on
the data bus.
RESET
The RESET input is used to reset the AD7641 and generate a
fast initialization. A rising edge on RESET aborts the current
conversion (if any) and tristates the data bus. The falling edge of
RESET clears the data bus and engages the initialization process
indicated by pulsing BUSY high. Conversions can take place
after the falling edge of BUSY. Refer to Figure 30 for the RESET
timing details.
t9
RESET
CNVST
DATA
BUSY
t38
t39
t8
Figure 30. RESET Timing
AD7641
PARALLEL INTERFACE
The AD7641 is configured to use the parallel interface for an
18-bit, 16-bit, or 8-bit bus width according to Table 7.
Master Parallel Interface
Data can be continuously read by tying CS and RD low, thus
requiring minimal microprocessor connections. However, in
this mode, the data bus is always driven and cannot be used in
shared bus applications, unless the device is held in RESET.
Figure 31 details the timing for this mode.
CS = RD = 0
t1
CNVST
BUSY
t3
t10
t4
t11
DATA
BUS
PREVIOUS CONVERSION DATA
NEW DATA
Figure 31. Master Parallel Data Timing for Reading (Continuous Read)
Slave Parallel Interface
In slave parallel reading mode, the data can be read either after
each conversion, which is during the next acquisition phase, or
during the following conversion, as shown in Figure 32 and
Figure 33, respectively. When the data is read during the
conversion, it is recommended that it is read-only during the
first half of the conversion phase. This avoids any potential
feedthrough between voltage transients on the digital interface
and the most critical analog conversion circuitry.
CS
RD
BUSY
DATA
BUS
CURRENT
CONVERSION
t12
t13
Figure 32. Slave Parallel Data Timing for Reading (Read After Convert)
Rev. 0 | Page 21 of 28
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