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參數資料
| 型號： | AD7665AST |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 16-Bit, 570 kSPS CMOS ADC |
| 中文描述： | 4-CH 16-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL/PARALLEL ACCESS, PQFP48 |
| 封裝： | LOW PROFILE, MS-026BBC, QFP-48 |
| 文件頁數： | 12/24頁 |
| 文件大小： | 348K |
| 代理商： | AD7665AST |
REV. 0
AD7665
–12–
SW
A
COMP
SW
B
IND
4R
REF
REFGND
LSB
MSB
32,768C
INGND
16,384C
4C
2C
C
C
CONTROL
LOGIC
SWITCHES
CONTROL
BUSY
OUTPUT
CODE
INC
4R
INA
R
INB
2R
CNVST
65,536C
Figure 3. ADC Simplified Schematic
CIRCUIT INFORMATION
The AD7665 is a fast, low-power, single-supply, precise 16-bit
analog-to-digital converter (ADC). The AD7665 features different
modes to optimize performances according to the applications.
In Warp mode, the AD7665 is capable of converting 570,000
samples per second (570 kSPS).
The AD7665 provides the user with an on-chip track/hold,
successive approximation ADC that does not exhibit any pipe-
line or latency, making it ideal for multiple multiplexed channel
applications.
It is specified to operate with both bipolar and unipolar input
ranges by changing the connection of its input resistive scaler.
The AD7665 can be operated from a single 5 V supply and be
interfaced to either 5 V or 3 V digital logic. It is housed in a
48-lead LQFP package that combines space savings and flexible
configurations as either serial or parallel interface. The AD7665
is a pin-to-pin-compatible upgrade of the AD7663 and AD7664.
CONVERTER OPERATION
The AD7665 is a successive approximation analog-to-digital
converter based on a charge redistribution DAC. Figure 3 shows
the simplified schematic of the ADC. The input analog signal is,
first, scaled down and level-shifted by the internal input resistive
scaler which allows both unipolar ranges (0 V to 2.5 V, 0 V to
5 V, and 0 to 10 V) and bipolar ranges (
±
2.5 V,
±
5 V, and
±
10 V).
The output voltage range of the resistive scaler is always 0 V to
2.5 V. The capacitive DAC consists of an array of 16 binary
weighted capacitors and an additional “LSB” capacitor. The
comparator’s negative input is connected to a “dummy” capaci-
tor of the same value as the capacitive DAC array.
During the acquisition phase, the common terminal of the array
tied to the comparator’s positive input is connected to AGND
via SW
A
. All independent switches are connected to the output
of the resistive scaler. Thus, the capacitor array is used as a
sampling capacitor and acquires the analog signal. Similarly, the
“dummy” capacitor acquires the analog signal on INGND input.
When the acquisition phase is complete, and the
CNVST
input
goes or is low, a conversion phase is initiated. When the conversion
phase begins, SW
A
and SW
B
are opened first. The capacitor array
and the “dummy” capacitor are then disconnected from the inputs
and connected to the REFGND input. Therefore, the differen-
tial voltage between the output of the resistive scaler and INGND
captured at the end of the acquisition phase is applied to the
comparator inputs, causing the comparator to become unbalanced.
By switching each element of the capacitor array between
REFGND or 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 first,
in order to bring the comparator back into a balanced condition.
After the completion of this process, the control logic generates
the ADC output code and brings BUSY output low.
Modes of Operation
The AD7665 features three modes of operations, Warp, Normal,
and Impulse. Each of these modes is more suitable for specific
applications.
The Warp mode allows the fastest conversion rate up to 570 kSPS.
However, in this mode, and this mode only, the full specified accu-
racy is guaranteed only when the time between conversion does
not exceed 1 ms. If the time between two consecutive conversions
is longer than 1 ms, for instance, after power-up, the first conver-
sion result should be ignored. This mode makes the AD7665
ideal for applications where both high accuracy and fast sample
rate are required.
The normal mode is the fastest mode (500 kSPS) without any
limitation about the time between conversions. This mode makes
the AD7665 ideal for asynchronous applications such as data
acquisition systems, where both high accuracy and fast sample
rate are required.
The impulse mode, the lowest power dissipation mode, allows
power saving between conversions. The maximum throughput
in this mode is 444 kSPS. When operating at 100 SPS, for ex-
ample, it typically consumes only 15
μ
W. This feature makes the
AD7665 ideal for battery-powered applications.
Transfer Functions
Using the OB/
2C
digital input, the AD7665 offers two output
codings: straight binary and two’s complement. The ideal transfer
characteristic for the AD7665 is shown in Figure 4 and Table III.
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
Figure 4. ADC Ideal Transfer Function
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| AD7665ASTRL | 16-Bit, 570 kSPS CMOS ADC |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ad7665astrl | 制造商:Analog Devices 功能描述:ADC SGL SAR 570KSPS 16BIT PARALLEL/SERL 48LQFP - Tape and Reel 制造商:Rochester Electronics LLC 功能描述:16-BIT, 500 KSPS CMOS A/D CONVERTER - Tape and Reel |
| AD7665ASTZ | 功能描述:IC ADC 16BIT CMOS 5V 48-LQFP 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 系列:- 位數:14 采樣率（每秒）:83k 數據接口:串行，并聯 轉換器數目:1 功率耗散（最大）:95mW 電壓電源:雙 ± 工作溫度:0°C ~ 70°C 安裝類型:通孔 封裝/外殼:28-DIP（0.600"，15.24mm） 供應商設備封裝:28-PDIP 包裝:管件 輸入數目和類型:1 個單端，雙極 |
| AD7665ASTZ | 制造商:Analog Devices 功能描述:A/D Converter (A-D) IC |
| AD7665ASTZRL | 功能描述:IC ADC 16BIT CMOS 5V 48-LQFP 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 系列:microPOWER™ 位數:8 采樣率（每秒）:1M 數據接口:串行，SPI? 轉換器數目:1 功率耗散（最大）:- 電壓電源:模擬和數字 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應商設備封裝:24-VQFN 裸露焊盤（4x4） 包裝:Digi-Reel® 輸入數目和類型:8 個單端，單極 產品目錄頁面:892 (CN2011-ZH PDF) 其它名稱:296-25851-6 |
| AD7666 | 制造商:AD 制造商全稱:Analog Devices 功能描述:16-Bit 1 MSPS SAR Unipolar ADC with Ref |
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