AD7328BRUZ(2004) 데이터 시트보기 (PDF) - Analog Devices
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AD7328BRUZ
(Rev.:2004)
(Rev.:2004)
Analog Devices
AD7328BRUZ Datasheet PDF : 24 Pages
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AD7328
the selected channel with a 50 kHz signal. The figure given is
the worst-case across all eight channels for the AD7328.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with non-linearities will create distortion
products at sum and difference frequencies of mfa ± nfb where
m, n = 0, 1, 2, 3, etc. Intermodulation distortion terms are those
for which neither m nor n are equal to zero. For example, the
second order terms include (fa + fb) and (fa – fb), while the
third order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa
– 2fb).
The AD7328 is tested using the CCIF standard where two input
frequencies near the top end of the input bandwidth are used.
In this case, the second order terms are usually distanced in
frequency from the original sine waves while the third order
terms are usually at a frequency close to the input frequencies.
As a result, the second and third order terms are specified
separately. The calculation of the intermodulation distortion is
as per the THD specification where it is the ratio of the rms
sum of the individual distortion products to the rms amplitude
of the sum of the fundamentals expressed in dBs.
PSR (Power Supply Rejection)
Variations in power supply will affect the full-scale transition
but not the converter’s linearity. Power supply rejection is the
maximum change in full-scale transition point due to a change
in power supply voltage from the nominal value. See Typical
Performance Curves.
Theory of Operation
CIRCUIT INFORMATION
The AD7328 is a fast, 8-Channel, 12-bit plus sign, bipolar Input,
serial A/D converter. The AD7328 can accept bipolar input
ranges that include ±10V, ±5V, ±2.5V, it can also accept 0 to 10V
unipolar input range. A different Analog input range can be
programmed on each analog input channel via the on-chip
registers. The AD7328 has a high speed serial interface that can
operate at throughput rates up to 1 MSPS.
The AD7328 requires VDD and VSS dual supplies for the high
voltage Analog input structures. These supplies must be equal to
or greater than the Analog input range. See Table 5 for the
requirements on these supplies for each Analog Input Range.
The AD7328 requires a low voltage 2.7V to 5.25 V VCC supply to
power the ADC core.
Preliminary Technical Data
Selected
Analog
Input
Range (V)
±10
±5
±2.5
0 to 10
Reference Full
AVCC
Voltage Scale
(V)
(V)
Input
Range(V)
2.5
±10
3/5
3.0
±12
3/5
2.5
±5
3/5
3.0
±6
3/5
2.5
±2.5
3/5
3.0
±3
3/5
2.5
0 to 10 3/5
3.0
0 to 12 3/5
Minimum
VDD/VSS (V)
±10
±12
±5
±6
±5
±5
+10/AGND
+12/AGND
Table 5. Reference and Supply Requirements for each Analog Input
Range
In order to meet the specified performance specifications when
the AD7328 is configured with the minimum VDD and VSS
supplies for a chosen Analog input range the throughput rate
should be decreased from the maximum throughput range. See
typical performance curves.
The Analog Inputs can be configured as either 8 Single-Ended
inputs, 4 True Differential Inputs, 4 Pseudo Differential Inputs
or 7 Pseudo Differential Inputs. Selection can be made by
programming the Mode bits, Mode0 and Mode1, in the Control
Register.
The serial clock input accesses data from the part but also
provides the clock source for each successive approximation
ADC. The AD7328 has an on-chip 2.5 V reference. However the
AD7328 can also work with an external Reference. On power up
the external reference operation is the default option. If the
internal Reference is the preferred option the user must write to
the reference bit in the control register to select the internal
Reference operation.
The AD7328 also features power-down options to allow power
saving between conversions. The power-down modes are
selected by programming the on-chip Control Register, as
described in the Modes of Operation section.
Rev. PrK | Page 10 of 24
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