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參數(shù)資料
| 型號： | AD280 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Universal Multichannel Industrial Signal Conditioning ADC(通用,多通道,工業(yè)信號調節(jié)A/D轉換器) |
| 中文描述： | 工業(yè)通用多通道ADC的信號調理（通用，多通道，工業(yè)信號調節(jié)的A / D轉換器） |
| 文件頁數(shù)： | 9/12頁 |
| 文件大小： | 150K |
| 代理商： | AD280 |
AD280
–9–
REV. 0
3.3
m
F
16V
TECHNCAL
DATA
tions where the microcontroller or other interface circuitry can
be operated bidirectionally.
The DRDY signal is a duplication of the DRDY bit in the status
byte. It is provided as an external pin in applications where a
signal is required to generate an interrupt at the end of the con-
version cycle.
CHARGE PUMP
The AD280 contains an internal charge pump circuit, which
eliminates the need for a negative power supply voltage. The
charge pump operates at 1/64th of the clock frequency. Because
of clock noise and the high current spikes generated by any
charge pump, it can be expected that the use of the charge pump
will somewhat degrade the performance (accuracy and resolu-
tion) of the AD280; for the most stringent and demanding ap-
plications, an external negative supply is preferred.
The charge pump requires the use of two external capacitors, as
shown in Figure 6. One of these capacitors is a shunt element,
and is connected from Pin 38 to ground. The other is a series
element, and is connected between Pin 39 and Pin 41. These
capacitors should be low ESR Tantalum types for the lowest
supply ripple and best performance; standard tantalum types, or
most aluminum types, should be avoided. A suggested capacitor
value is 3.3
μ
F, although the charge pump is unconditionally
stable, and larger values may be used.
41
39
6
38
3.3
F
16V
+
C1
C2
ALO
C3
AD280
Figure 6. Charge Pump Connections
INTERFACE EXAMPLES
Figure 7 is an example of how the AD280 can be configured to
accept an array of input configurations for thermocouples,
RTD’s, millivolt and voltage inputs. In this example, the excita-
tion sources are connected in such a way that just EXC0 and
EXC1 would be enabled for the RTD interconnect, but all four
could be enabled at the +25 nA or –25 nA level for open lead
detection. Although not shown, it would also be quite possible
to connect a single RTD and two other single-ended inputs,
such as thermocouples, millivolt or voltage signals.
SERIAL PERIPHERAL INTERFACE
The AD280 features a Serial Peripheral Interface (SPI) that
enables bidirectional half duplex communication with a micro-
controller or microcomputer. The interface consists of five
signals:
CE
DI
Data Input
DO
Data Output
SK
Shift Clock
DRDY
Data Ready
Since the DO pin will always be three-stated, except during a
“read” command, it may be tied to DI (Data Input) in applica-
RTD
RTD
TC0
TC1
TC2
TC3
CJC
SENSOR
EXC0
EXC2
EXC1
EXC3
GND SNSE
AGND
CJCIN
AIN0
AIN1
AIN2
AIN3
AD280
Figure 7. Example of “Universal” Input Connection Arrangement for the AD280
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