參數(shù)資料
型號(hào)： EVAL-AD7667CBZ
廠商： Analog Devices Inc
文件頁(yè)數(shù)： 11/28頁(yè)
文件大?。?/td> 0K
描述： BOARD EVALUATION FOR AD7667
標(biāo)準(zhǔn)包裝： 1
系列： PulSAR®
ADC 的數(shù)量： 1
位數(shù)： 16
采樣率（每秒）： 1M
數(shù)據(jù)接口： 串行，并聯(lián)
輸入范圍： ±VREF
在以下條件下的電源（標(biāo)準(zhǔn)）： 133mW @ 1MSPS
工作溫度： -40°C ~ 85°C
已用 IC / 零件： AD7667
已供物品： 板
相關(guān)產(chǎn)品： AD7667ACPZ-ND - IC ADC 16BIT UNIPOLAR 48LFCSP
AD7667ACPZRL-ND - IC ADC 16BIT UNIPOLAR 48LFCSP
AD7667ASTZRL-ND - IC ADC 16BIT UNIPOLAR 48LQFP
AD7667ASTZ-ND - IC ADC 16BIT UNIPOLAR 48-LQFP
AD7667
Rev. 0 | Page 19 of 28
The noise generated by the driver amplifier needs to be
kept as low as possible in order to preserve the SNR and
transition noise performance of the AD7667. The noise
coming from the driver is filtered by the AD7667 analog
input circuit 1-pole low-pass filter made by R1 and C2 or
by the external filter, if one is used. The SNR degradation
due to the amplifier is
π
+
=
2
3
)
(
2
784
28
log
20
N
dB
LOSS
Ne
f
SNR
where:
f–3dB
is the input bandwidth of the AD7667 (13 MHz) or
the cutoff frequency of the input filter (3.9 MHz), if
one is used.
N
is the noise factor of the amplifier (+1 in buffer
configuration).
eN
is the equivalent input noise voltage of the op amp, in
nV/√Hz.
For instance, a driver with an equivalent input noise of
2 nV/√Hz, like the AD8021 with a noise gain of +1 when
configured as a buffer, degrades the SNR by only 0.13 dB
when using the filter in Figure 26 and by 0.43 dB without.
The driver needs to have a THD performance suitable to
that of the AD7667. Figure 15 gives the THD versus
frequency that the driver should exceed.
The AD8021 meets these requirements and is appropriate for
almost all applications. The AD8021 needs a 10 pF external
compensation capacitor that should have good linearity as an
NPO ceramic or mica type. Moreover, the use of a noninverting
+1 gain arrangement is recommended and helps to obtain the
best signal-to-noise ratio.
The AD8022 could also be used if a dual version is needed and
gain of 1 is present. The AD829 is an alternative in applications
where high frequency (above 100 kHz) performance is not
required. In gain of 1 applications, it requires an 82 pF
compensation capacitor. The AD8610 is an option when low
bias current is needed in low frequency applications.
Voltage Reference Input
The AD7667 allows the choice of either a very low temperature
drift internal voltage reference or an external 2.5 V reference.
Unlike many ADCs with internal references, the internal
reference of the AD7667 provides excellent performance and
can be used in almost all applications.
To use the internal reference along with the internal buffer,
PDREF and PDBUF should both be LOW. This produces 1.2 V
on REFBUFIN which, amplified by the buffer, results in a 2.5 V
reference on the REF pin.
The output impedance of REFBUFIN is 11 k (minimum)
when the internal reference is enabled. It is necessary to
decouple REFBUFIN with a ceramic capacitor greater than
10 nF. Thus the capacitor provides an RC filter for noise
reduction.
To use an external reference along with the internal buffer,
PDREF should be HIGH and PDBUF should be LOW. This
powers down the internal reference and allows the 2.5 V
reference to be applied to REFBUFIN.
To use an external reference directly on REF pin, PDREF and
PDBUF should both be HIGH.
PDREF and PDBUF power down the internal reference and the
internal reference buffer, respectively. Note that the PDREF and
PDBUF input current should never exceed 20 mA. This could
eventually occur when input voltage is above AVDD (for
instance, at power-up). In this case, a 100 series resistor is
recommended.
The internal reference is temperature compensated to 2.5 V
±7 mV. The reference is trimmed to provide a typical drift of
3 ppm/°C . This typical drift characteristic is shown in
Figure 22. For improved drift performance, an external
reference, such as the AD780, can be used.
The AD7667 voltage reference input REF has a dynamic input
impedance; it should therefore be driven by a low impedance
source with efficient decoupling between the REF and
REFGND inputs. This decoupling depends on the choice of the
voltage reference but usually consists of a low ESR tantalum
capacitor connected to REF and REFGND with minimum
parasitic inductance. A 10 F (X5R, 1206 size) ceramic chip
capacitor (or 47 F tantalum capacitor) is appropriate when
using either the internal reference or one of these
recommended reference voltages:
The low noise, low temperature drift ADR421 and AD780
The low power ADR291
The low cost AD1582
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EVAL-AD7671CBZ 功能描述:BOARD EVALUATION FOR AD7671 RoHS:是 類別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 模數(shù)轉(zhuǎn)換器 (ADC) 系列:PulSAR® 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- ADC 的數(shù)量:1 位數(shù):12 采樣率（每秒）:94.4k 數(shù)據(jù)接口:USB 輸入范圍:±VREF/2 在以下條件下的電源（標(biāo)準(zhǔn)）:- 工作溫度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，軟件
EVAL-AD7671EDZ 功能描述:BOARD EVAL FOR AD7671 RoHS:是 類別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 模數(shù)轉(zhuǎn)換器 (ADC) 系列:* 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- ADC 的數(shù)量:1 位數(shù):12 采樣率（每秒）:94.4k 數(shù)據(jù)接口:USB 輸入范圍:±VREF/2 在以下條件下的電源（標(biāo)準(zhǔn)）:- 工作溫度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，軟件
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