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參數資料
| 型號： | AD9240EB |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Complete 14-Bit, 10 MSPS Monolithic A/D Converter |
| 中文描述： | 完整的14位，10 MSPS的單片機的A / D轉換器 |
| 文件頁數： | 9/24頁 |
| 文件大?。?/td> | 328K |
| 代理商： | AD9240EB |
AD9240
REV. A
–9–
The addition of a differential input structure gives the user an
additional level of flexibility that is not possible with traditional
flash converters. The input stage allows the user to easily con-
figure the inputs for either single-ended operation or differential
operation. The A/D’s input structure allows the dc offset of the
input signal to be varied independently of the input span of the
converter. Specifically, the input to the A/D
core is the differ-
ence of the voltages applied at the VINA and VINB input pins.
Therefore, the equation,
V
CORE
= VINA – VINB
(1)
defines the output of the differential input stage and provides
the input to the A/D core.
The voltage,
V
CORE
, must satisfy the condition,
–
VREF
≤
V
CORE
≤
VREF
(2)
where
VREF
is the voltage at the
VREF
pin.
While an infinite combination of VINA and VINB inputs exist
that satisfy Equation 2, there is an additional limitation placed
on the inputs by the power supply voltages of the AD9240. The
power supplies bound the valid operating range for VINA and
VINB. The condition,
AVSS –
0.3
V < VINA < AVDD +
0.3
V
(3)
AVSS
– 0.3
V
<
VINB
<
AVDD
+ 0.3
V
where
AVSS
is nominally 0 V and
AVDD
is nominally +5 V,
defines this requirement. Thus, the range of valid inputs for
VINA and VINB is any combination that satisfies both Equa-
tions 2 and 3.
For additional information showing the relationship between
VINA, VINB, VREF and the digital output of the AD9240, see
Table IV.
Refer to Table I and Table II for a summary of the various
analog input and reference configurations
.
ANALOG INPUT OPERATION
Figure 24 shows the equivalent analog input of the AD9240
which consists of a differential sample-and-hold amplifier (SHA).
The differential input structure of the SHA is highly flexible,
allowing the devices to be easily configured for either a differen-
tial or single-ended input. The dc offset, or common-mode
voltage, of the input(s) can be set to accommodate either single-
supply or dual supply systems. Note also that the analog inputs,
VINA and VINB, are interchangeable with the exception that
reversing the inputs to the VINA and VINB pins results in a
polarity inversion.
VINA
VINB
C
PIN
+
C
PAR
C
PIN
–
C
PAR
Q
S1
Q
S1
Q
H1
C
S
C
S
C
H
C
H
Q
S2
Q
S2
Figure 24. Simplified Input Circuit
The input SHA of the AD9240 is optimized to meet the perfor-
mance requirements for some of the most demanding commu-
nication, imaging, and data acquisition applications while
maintaining low power dissipation. Figure 25 is a graph of the
full-power bandwidth of the AD9240, typically 60 MHz. Note
that the small signal bandwidth is the same as the full-power
bandwidth. The settling time response to a full-scale stepped
input is shown in Figure 26 and is typically less than 40 ns to
0.0025%. The low input referred noise of 0.36 LSB’s rms is
displayed via a grounded histogram and is shown in Figure 13.
FREQUENCY – MHz
1
0
–7
1
10
100
–3
–4
–5
–6
–1
–2
–8
–9
–10
A
Figure 25. Full-Power Bandwidth
SETTLING TIME – ns
C
16000
12000
00
60
10
20
30
40
50
8000
4000
70
80
Figure 26. Settling Time
The SHA’s optimum distortion performance for a differential or
single-ended input is achieved under the following two condi-
tions: (1) the common-mode voltage is centered around mid-
supply (i.e., AVDD/2 or approximately 2.5 V) and (2) the input
signal voltage span of the SHA is set at its lowest (i.e., 2 V input
span). This is due to the sampling switches, Q
S1
, being CMOS
switches whose R
ON
resistance is very low but has some signal
dependency which causes frequency dependent ac distortion
while the SHA is in the track mode. The R
ON
resistance of a
CMOS switch is typically lowest at its midsupply but increases
symmetrically as the input signal approaches either AVDD or
AVSS. A lower input signal voltage span centered at midsupply
reduces the degree of R
ON
modulation.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD9240-EB | 制造商:Analog Devices 功能描述: |
| AD9241 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Complete 14-Bit, 1.25 MSPS Monolithic A/D Converter |
| AD9241ACHIPS | 制造商:Analog Devices 功能描述: |
| AD9241AS | 制造商:Analog Devices 功能描述:ADC Single Pipelined 1.25Msps 14-bit Parallel 44-Pin MQFP 制造商:Rochester Electronics LLC 功能描述:14BIT 1.25 MSPS MONOLITHIC A/D CONVERTER - Bulk 制造商:Analog Devices 功能描述:IC 14-BIT ADC |
| AD9241ASRL | 制造商:Analog Devices 功能描述:ADC Single Pipelined 1.25Msps 14-bit Parallel 44-Pin MQFP T/R |
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