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參數資料
| 型號： | AD7694 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 16-Bit, 250 kSPS PulSAR ADC in MSOP |
| 中文描述： | 16位，250 kSPS的PulSAR系列ADC的，采用MSOP |
| 文件頁數： | 12/16頁 |
| 文件大小： | 281K |
| 代理商： | AD7694 |
AD7694
APPLICATION INFORMATION
Rev. 0 | Page 12 of 16
SW+
MSB
16,384C
IN+
LSB
COMP
CONTROL
LOGIC
SWITCHES CONTROL
BUSY
OUTPUT CODE
CNV
REF
GND
IN–
4C
2C
C
C
32,768C
SW–
MSB
16,384C
LSB
4C
2C
C
C
32,768C
0
Figure 18. ADC Simplified Schematic
CIRCUIT INFORMATION
The AD7694 is a low power, single-supply, 16-bit ADC using a
successive approximation architecture. It is capable of con-
verting 250,000 samples per second (250 kSPS) and powers
down between conversions. When operating at 100 SPS, for
example, it consumes typically 4 μW, ideal for battery-powered
applications.
The AD7694 provides the user with on-chip track-and-hold and
does not exhibit any pipeline delay or latency, making it ideal
for multiple, multiplexed channel applications.
The AD7694 is specified from 2.7 V to 5.25 V. It is housed in a
8-lead MSOP. The AD7694 is an improved second source to
LTC1864 and LTC1864L. For even better performance, the
AD7685
should be considered.
CONVERTER OPERATION
The AD7694 is a successive approximation ADC based on a
charge redistribution DAC. Figure 18 shows the simplified
schematic of the ADC. The capacitive DAC consists of two
identical arrays of 16 binary weighted capacitors, which are
connected to the two comparator inputs.
During the acquisition phase, terminals of the array tied to the
comparator’s input are connected to GND via SW+ and SW.
All independent switches are connected to the analog inputs.
Thus, the capacitor arrays are used as sampling capacitors and
acquire the analog signal on the IN+ and IN inputs. When the
acquisition phase is complete and the CNV input goes high, a
conversion phase begins. When the conversion phase begins,
SW+ and SW are opened first. The two capacitor arrays are
then disconnected from the inputs and connected to the GND
input. Thus, the differential voltage between the inputs, IN+ and
IN, captured at the end of the acquisition phase applies to the
comparator inputs, causing the comparator to become unbal-
anced. By switching each element of the capacitor array between
GND and REF, the comparator input varies by binary weighted
voltage steps (V
REF
/2, V
REF
/4...V
REF
/65536). The control logic
toggles these switches, starting with the MSB, in order 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.
Because the AD7694 has an on-board conversion clock, the
serial clock, SCK, is not required for the conversion process.
TRANSFER FUNCTIONS
The ideal transfer function for the AD7694 is shown in
Figure 19 and Table 8.
000...000
000...001
000...010
111...101
111...110
111...111
A
ANALOG INPUT
+FS – 1.5 LSB
+
FS – 1 LSB
–FS + 1 LSB
–FS
–FS + 0.5 LSB
0
Figure 19. ADC Ideal Transfer Function
Table 8. Output Codes and Ideal Input Voltages
Analog Input
V
REF
= 5 V
FSR – 1 LSB
4.999924 V
Midscale + 1 LSB
2.500076 V
Midscale
2.5 V
Midscale – 1 LSB
2.499924 V
–FSR + 1 LSB
76.3 μV
–FSR
0 V
Description
Digital Output Code
Hexadecimal
FFFF
2
8001
8000
7FFF
0001
0000
3
2
This is also the code for an overranged analog input (V
IN+
– V
IN–
above
V
REF
– V
GND
).
3
This is also the code for an underranged analog input (V
IN+
– V
IN–
below V
GND
).
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| AD7694ARMZRL7 | 功能描述:IC ADC 16BIT SAR 250KSPS 8-MSOP RoHS:是 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:PulSAR® 標準包裝:1,000 系列:- 位數:16 采樣率（每秒）:45k 數據接口:串行 轉換器數目:2 功率耗散（最大）:315mW 電壓電源:模擬和數字 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:28-SOIC（0.295"，7.50mm 寬） 供應商設備封裝:28-SOIC W 包裝:帶卷 (TR) 輸入數目和類型:2 個單端，單極 |
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