參數(shù)資料
型號(hào): AD7691
廠商: Analog Devices, Inc.
英文描述: 18-Bit, 1.5 LSB INL, 250 kSPS PulSAR Differential ADC in MSOP/QFN
中文描述: 18位,1.5 LSB INL和250 kSPS的PulSAR系列差分ADC,采用MSOP / QFN封裝
文件頁(yè)數(shù): 16/28頁(yè)
文件大?。?/td> 682K
代理商: AD7691
AD7691
Table 9. Recommended Driver Amplifiers
Amplifier
Typical Application
ADA4941-1
Very low noise, low power single-ended-to-
differential driver
ADA4841-x
Very low noise, small, and low power
AD8655
5 V single supply, low noise
AD8021
Very low noise and high frequency
AD8022
Low noise and high frequency
OP184
Low power, low noise, and low frequency
AD8605, AD8615
5 V single supply, low power
SINGLE-TO-DIFFERENTIAL DRIVER
For applications using a single-ended analog signal, either
bipolar or unipolar, the ADA4941-1 single-ended-to-differential
driver allows for a differential input into the part. The schematic
is shown in Figure 30.
Rev. 0 | Page 16 of 28
R1 and R2 set the attenuation ratio between the input range and
the ADC range (V
REF
). R1, R2, and C
F
are chosen depending on
the desired input resistance, signal bandwidth, antialiasing, and
noise contribution. For example, for the ±10 V range with a 4 kΩ
impedance, R2 = 1 kΩ and R1 = 4 kΩ.
R3 and R4 set the common mode on the IN input, and R5 and
R6 set the common mode on the IN+ input of the ADC. The
common mode should be set close to V
REF
/2; however, if single
supply is desired, it can be set slightly above V
REF
/2 to provide
some headroom for the ADA4941-1 output stage. For example,
for the ±10 V range with a single supply, R3 = 8.45 kΩ, R4 =
11.8 kΩ, R5 = 10.5 kΩ, and R6 = 9.76 kΩ.
AD7691
REF
GND
VDD
IN+
2.7nF
100nF
2.7nF
IN–
+5V REF
±10V, ±5V, ...
+5.2V
+5.2V
15
10μF
15
R2
C
F
ADA4941
R1
R3
100nF
R5
R4
R6
0
Figure 30. Single-Ended-to-Differential Driver Circuit
VOLTAGE REFERENCE INPUT
The AD7691 voltage reference input, REF, has a dynamic input
impedance and should therefore be driven by a low impedance
source with efficient decoupling between the REF and GND
pins, as explained in the Layout section.
When REF is driven by a very low impedance source, for
example, a reference buffer using the AD8031 or the AD8605, a
10 μF (X5R, 0805 size) ceramic chip capacitor is appropriate for
optimum performance.
If an unbuffered reference voltage is used, the decoupling value
depends on the reference used. For instance, a 22 μF (X5R,
1206 size) ceramic chip capacitor is appropriate for optimum
performance using a low temperature drift ADR43x reference.
If desired, smaller reference decoupling capacitor values—down
to 2.2 μF—can be used with a minimal impact on performance,
especially DNL.
Regardless, there is no need for an additional lower value
ceramic decoupling capacitor (for example, 100 nF) between the
REF and GND pins.
POWER SUPPLY
The AD7691 uses two power supply pins: a core supply, VDD,
and a digital input/output interface supply, VIO. VIO allows
direct interface with any logic between 1.8 V and VDD. To
reduce the supplies needed, the VIO and VDD pins can be tied
together. The AD7691 is independent of power supply sequencing
between VIO and VDD. Additionally, it is very insensitive to
power supply variations over a wide frequency range, as shown
in Figure 31.
95
65
1
10000
FREQUENCY (kHz)
P
90
85
80
75
70
10
100
1000
0
Figure 31. PSRR vs. Frequency
相關(guān)PDF資料
PDF描述
AD7691BRMZ 18-Bit, 1.5 LSB INL, 250 kSPS PulSAR Differential ADC in MSOP/QFN
AD7691BRMZ-RL7 18-Bit, 1.5 LSB INL, 250 kSPS PulSAR Differential ADC in MSOP/QFN
AD7710AN Signal Conditioning ADC
AD7710AQ Signal Conditioning ADC
AD7710AR Signal Conditioning ADC
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