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| 型号： | EVAL-AD7944EBZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 5/28页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR AD7944 |
| 标准包装： | 1 |
| 系列： | PulSAR® |
| ADC 的数量： | 1 |
| 位数： | 14 |
| 采样率（每秒）： | 2.5M |
| 数据接口： | SPI?、QSPI?、MICROWIRE? 和 DSP |
| 输入范围： | 0 ~ 5 V |
| 工作温度： | -40°C ~ 85°C |
| 已用 IC / 零件： | AD7944 |
| 已供物品： | 板 |
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AD7944
Rev. A | Page 13 of 28
THEORY OF OPERATION
COMP
SWITCHES CONTROL
BUSY
OUTPUT CODE
CNV
CONTROL
LOGIC
SW+
LSB
SW–
LSB
IN+
REF
REFGND
IN–
MSB
C
4C
2C
4096C
8192C
C
4C
2C
4096C
8192C
04658-
005
Figure 21. ADC Simplified Schematic
CIRCUIT INFORMATION
The AD7944 is a fast, low power, single-supply, precise, 14-bit
ADC using a successive approximation architecture. The AD7944
features different modes to optimize performance according to the
application. In turbo mode, the AD7944 is capable of converting
2,500,000 samples per second (2.5 MSPS).
The AD7944 provides the user with an on-chip track-and-hold
and does not exhibit any pipeline delay or latency, making it
ideal for multiple multiplexed channel applications.
The AD7944 can be interfaced to any 1.8 V to 2.7 V digital logic
family. It is available in a space-saving 20-lead LFCSP that allows
flexible configurations. It is pin-for-pin compatible with the
CONVERTER OPERATION
The AD7944 is a successive approximation ADC based on a
charge redistribution DAC. Figure 21 shows the simplified
schematic of the ADC. The capacitive DAC consists of two
identical arrays of 14 binary-weighted capacitors that are
connected to the two comparator inputs.
During the acquisition phase, the terminals of the array tied to
the input of the comparator are connected to AGND via SW+
and SW. All independent switches are connected to the analog
inputs. Therefore, the capacitor arrays are used as sampling
capacitors and acquire the analog signal on the IN+ and IN
inputs. When the acquisition phase is completed and the CNV
input goes high, a conversion phase is initiated.
When the conversion phase begins, SW+ and SW are opened
first. The two capacitor arrays are then disconnected from the
analog inputs and connected to the REFGND input. Therefore,
the differential voltage between the IN+ and IN inputs captured
at the end of the acquisition phase is applied to the comparator
inputs, causing the comparator to become unbalanced. By switch-
ing each element of the capacitor array between REFGND and
REF, the comparator input varies by binary-weighted voltage
steps (VREF/2, VREF/4, … VREF/16,384). The control logic toggles
these switches, starting with the MSB, to bring the comparator
back into a balanced condition. After the completion of this
process, the part returns to the acquisition phase, and the control
logic generates the ADC output code and a busy signal indicator.
Because the AD7944 has an on-board conversion clock, the
serial clock, SCK, is not required for the conversion process.
CONVERSION MODES OF OPERATION
The AD7944 features two conversion modes of operation:
turbo and normal. Turbo conversion mode (TURBO high)
allows the fastest conversion rate of up to 2.5 MSPS and does
not power down between conversions. The first conversion in
turbo mode should be ignored because it contains meaningless
data. For applications that require lower power and slightly
slower sampling rates, the normal conversion mode (TURBO
low) allows a maximum conversion rate of 2.0 MSPS and
powers down between conversions. The first conversion in
normal mode contains meaningful data.
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| EVAL-AD7949CBZ | 制造商:Analog Devices 功能描述:EVAL BOARD 8 CH 250KSPS 14BIT ADC IC. - Bulk |
| EVAL-AD7949EDZ | 功能描述:BOARD EVAL AD7949 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-AD7951EDZ | 功能描述:BOARD EVAL FOR AD7951 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 |
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