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參數資料
| 型號： | AD7994 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 4-Channel, 12-/10-Bit ADCs with I2C Compatible Interface in 16-Lead TSSOP |
| 中文描述： | 4通道，12-/10-Bit ADC的16 - I2C兼容接口的無鉛TSSOP封裝 |
| 文件頁數： | 13/27頁 |
| 文件大小： | 277K |
| 代理商： | AD7994 |
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AD7994/AD7993
–13–
REV. PrF
PRELIMINARY TECHNICAL DATA
CIRCUIT INFORMATION
The AD7994/AD7993 are fast, low-power, 12-/10-bit,
single supply, 4 Channel A/D converters respectively. The
parts can be operated from a 2.7 V to 5.5 V supply.
The AD7994/AD7993 provide the user with a 4-channel
multiplexer, an on-chip track/hold, A/D converter, an on-
chip oscillator, internal data registers and an I
2
C compat-
ible serial interface, all housed in a 16-lead TSSOP
package, which offers the user considerable space saving
advantages over alternative solutions. An external reference
is required by the AD7994/AD7993, and this reference can
be in the range of 1.2 V to V
DD
.
The AD7994/AD7993 will normally remain in a power-
down state while not converting. When supplies are first
applied the part will come up in a shutdown state. Power-
up is intitiated prior to a conversion and the device returns
to power-down upon completion of the conversion. Con-
versions can be initiated on the AD7994/AD7993 by either
pulsing the
CONVST
signal, using an automatic cycling
mode or using a mode where wake-up and conversion oc-
cur during the write function ( see modes of Operation
section). On completion of a conversion the AD7994/
AD7993 will enter shutdown mode again. This automatic
shutdown feature allows power saving between conversions.
This means any read or write operations across the I
2
C
interface can occur while the device is in shut-down.
ADC TRANSFER FUNCTION
The output coding of the AD7994/AD7993 is straight
binary. The designed code transitions occur at successive
integer LSB values (i.e., 1LSB, 2LSBs, etc.). The LSB
size for the AD7994 is = REF
IN
/4096 and REF
IN
/256 for
the AD7993 . The ideal transfer characteristic for the
AD7994/AD7993 is shown in Figure 4 below.
CONVERTER OPERATION
The AD7994/AD7993 are successive approximation ana-
log-to-digital converters based around a capacitive DAC.
Figures 2 and 3 show simplified schematics of the ADC
during its acquisition and conversion phase respectively.
Figure 2 shows the ADC during its acquisition phase.
SW2 is closed and SW1 is in position A, the comparator
is held in a balanced condition and the sampling capacitor
acquires the signal on V
IN
X.
When the ADC starts a conversion, see Figure 3, SW2
will open and SW1 will move to position B causing the
comparator to become unbalanced. The input is discon-
nected once the conversion begins. The Control Logic
and the Capacitive DAC are used to add and subtract
fixed amounts of charge from the sampling capacitor to
bring the comparator back into a balanced condition.
When the comparator is rebalanced the conversion is com-
plete. The Control Logic generates the ADC output code.
Figure 4 shows the ADC transfer function.
Figure 2. ADC Acquisition Phase
Figure 3. ADC Conversion Phase
Figure 4. AD7994/AD7993 Transfer Characteristic
TYPICAL CONNECTION DIAGRAM
Figure 5 shows the typical connection diagram for the
AD7994/AD7993. In Figure 5 the Address Select pin,
AS, is tied to V
DD
, however AS can also be either tied to
GND or left floating, allowing the user to select up to
three AD7994/AD7993 devices on the same serial bus. An
external reference must be applied to the AD7994/
AD7993. This reference can be in the range of 1.2 V to
V
DD
. A precision reference like the REF 19X family,
ADR421, ADR03, ADR381 can be used to supply the
Reference Voltage to the ADC.
SDA and SCL form the two-wire I
2
C/SMBus compatible
interface. External Pull-up resistors should be added to
the SDA and SCL bus lines.
The AD7994-0/AD7993-0 support Standard and Fast I
2
C
Interface Modes. While the AD7994-1/AD7993-1 support
Standard, Fast and High-speed I
2
C Interface Modes.
Therefore if operating the AD7994/AD7993 in either
Standard or Fast Mode, up to five AD7994/AD7993 de-
vices (3 x AD7994-0/AD7993-0 and 2 x AD7994-1/
AD7993-1 or 3 x AD7994-1/AD7993-1 and 2 x AD7994-
0/AD7993-0) can be connected to the bus. When operat-
ing in Hs-Mode then up to three AD7994-1/AD7993-1
devices can be connected to the bus.
Wake-up from power-down prior to a conversion is ap-
proximately 1μs while conversion time is approximately
2μs. The AD7994/AD7993 enters power-down mode
again after each conversion, this will be useful in applica-
tions where power consumption is of concern.
CAPACITIVE
DAC
VIN
COMPARATOR
CONTROL
LOGIC
SW1
A
B
SW2
AGND
CAPACITIVE
DAC
VIN
COMPARATOR
CONTROL
LOGIC
SW1
A
B
SW2
AGND
000...000
A
ANALOG INPUT
0 V TO REFIN
111...111
111...110
000...001
000...010
111...000
011...111
AGND +1 LSB
+REFIN -1LSB
AD7994 1 LSB = REFIN/4096
AD7993 1 LSB = REFIN/256
相關PDF資料 |
PDF描述 |
|---|---|
| AD7993BRU-1 | 4-Channel, 12-/10-Bit ADCs with I2C Compatible Interface in 16-Lead TSSOP |
| AD7997 | 8-Channel, 10- and 12-Bit ADCs with I2CCompatible |
| AD7997BRU-0 | 8-Channel, 10- and 12-Bit ADCs with I2CCompatible |
| AD7997BRU-0REEL | 8-Channel, 10- and 12-Bit ADCs with I2CCompatible |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7994-0 | 制造商:AD 制造商全稱:Analog Devices 功能描述:4-Channel, 10- and 12-Bit ADCs with I2C Compatible Interface in 16-Lead TSSOP |
| AD7994-1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:4-Channel, 10- and 12-Bit ADCs with I2C Compatible Interface in 16-Lead TSSOP |
| AD7994BRU-0 | 功能描述:IC ADC 12BIT 4CHAN I2C 16TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 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 |
| AD7994BRU-0REEL | 功能描述:IC ADC 12BIT 4CHAN I2C 16TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 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 |
| AD7994BRU-1 | 制造商:Analog Devices 功能描述:ADC Single SAR 188ksps 12-bit Serial 16-Pin TSSOP 制造商:Rochester Electronics LLC 功能描述: |
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