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| 型号： | EVAL-AD7651CBZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 9/28页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR AD7651 |
| 标准包装： | 1 |
| 系列： | PulSAR® |
| ADC 的数量： | 1 |
| 位数： | 16 |
| 采样率（每秒）： | 100k |
| 数据接口： | 串行，并联 |
| 输入范围： | 0 ~ 2.5 V |
| 在以下条件下的电源（标准）： | 16mW @ 100kSPS |
| 工作温度： | -40°C ~ 85°C |
| 已用 IC / 零件： | AD7651 |
| 已供物品： | 板 |
| 相关产品： | AD7651ASTZ-ND - IC ADC 16BIT 100KSPS 48-LQFP AD7651ACPZ-ND - IC ADC 16BIT UNIPOLAR 48LFCSP AD7651ASTZRL-ND - IC ADC 16BIT UNIPOLAR 48LFCSP AD7651ACPZRL-ND - IC ADC 16BIT UNIPOLAR 48LQFP |
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AD7651
Driver Amplifier Choice
TYPICAL CONNECTION DIAGRAM
Although the AD7651 is easy to drive, the driver amplifier needs
to meet the following requirements:
Figure 22 shows a typical connection diagram for the AD7651.
Analog Input
The driver amplifier and the AD7651 analog input circuit
must be able to settle for a full-scale step of the capacitor
array at a 16-bit level (0.0015%). In the amplifier’s data
sheet, settling at 0.1% to 0.01% is more commonly speci-
fied. This could differ significantly from the settling time at
a 16-bit level and should be verified prior to driver
selection. The tiny op amp OP184, which combines ultra
low noise and high gain-bandwidth, meets this settling
time requirement.
Figure 23. Equivalent Analog Input Circuit
shows an equivalent circuit of the input structure of
the AD7651.
The two diodes, D1 and D2, provide ESD protection for the
analog inputs IN and INGND. Care must be taken to ensure
that the analog input signal never exceeds the supply rails by
more than 0.3 V. This will cause these diodes to become
forward-biased and start conducting current. These diodes can
handle a forward-biased current of 100 mA maximum. For
instance, these conditions could eventually occur when the
input buffer’s (U1) supplies are different from AVDD. In such a
case, an input buffer with a short-circuit current limitation can
be used to protect the part.
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 AD7651. The noise
coming from the driver is filtered by the AD7651 analog
input circuit 1-pole low-pass filter made by R1 and C2 or
by the external filter, if one is used.
C2
R1
D1
D2
C1
IN
OR INGND
AGND
AVDD
02965-0-008
The driver needs to have a THD performance suitable to
that of the AD7651.
usually appropriate for almost all applications. As an alternative,
in very high speed and noise-sensitive applications, the AD8021
with an external 10 pF compensation capacitor can be used.
This capacitor 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.
This analog input structure allows the sampling of the
differential signal between IN and INGND. Unlike other
converters, INGND is sampled at the same time as IN. By using
this differential input, small signals common to both inputs are
rejected. For instance, by using INGND to sense a remote signal
ground, ground potential differences between the sensor and
the local ADC ground are eliminated.
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.
During the acquisition phase, the impedance of the analog input
IN can be modeled as a parallel combination of capacitor C1
and the network formed by the series connection of R1 and C2.
C1 is primarily the pin capacitance. R1 is typically 3250 and is
a lumped component made up of some serial resistors and the
on resistance of the switches. C2 is typically 60 pF and is mainly
the ADC sampling capacitor. During the conversion phase,
where the switches are opened, the input impedance is limited
to C1. R1 and C2 make a 1-pole low-pass filter that reduces
undesirable aliasing effect and limits the noise.
When the source impedance of the driving circuit is low, the
AD7651 can be driven directly. Large source impedances will
significantly affect the ac performance, especially total
harmonic distortion.
Rev. 0 | Page 17 of 28
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相关代理商/技术参数 |
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|---|---|
| EVAL-AD7651EDZ | 功能描述:BOARD EVAL FOR AD7651 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
| EVAL-AD7652CB | 制造商:Analog Devices 功能描述:DEV TOOLS, 16BIT 500KSPS SAR UNIPOLAR ADC W/ REF - Bulk |
| EVAL-AD7652CBZ | 功能描述:BOARD EVALUATION FOR AD7652 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:PulSAR® 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
| EVAL-AD7652EDZ | 功能描述:BOARD EVAL FOR AD7652 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
| EVAL-AD7653CB | 制造商:Analog Devices 功能描述:Development Tools, 16Bit 1MSPS SAR Unipolar ADC with Ref 制造商:Analog Devices 功能描述:DEV TOOLS, 16BIT 1MSPS SAR UNIPOLAR ADC W/ REF - Bulk |
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