參數(shù)資料
型號： AD7746ARUZ-REEL7
廠商： Analog Devices, Inc.
元件分類： 溫度/濕度傳感器
英文描述： 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
中文描述： 24位的電容數(shù)字轉換器的溫度傳感器
文件頁數(shù)： 23/28頁
文件大?。?/td> 391K
代理商： AD7746ARUZ-REEL7
AD7745/AD7746
PARASITIC SERIAL RESISTANCE
Rev. 0| Page 23 of 28
DATA
CDC
EXC
R
S1
CIN
R
S2
C
X
0
Figure 39. Parasitic Serial Resistance
The AD7745/AD7746 CDC result is affected by a resistance in
series with the measured capacitance. The total serial resistance,
which refers to R
S1
+ R
S2
on Figure 39, should be less than 1 k
for the specified performance. See typical performance charac-
teristics shown in Figure 15.
CAPACITIVE GAIN CALIBRATION
The AD7745/AD7746 gain is factory calibrated for the full scale
of ±4.096 pF in the production for each part individually. The
factory gain coefficient is stored in a one-time programmable
(OTP) memory and is copied to the capacitive gain register at
power-up or after reset.
The gain can be changed by executing a capacitance gain
calibration mode, for which an external full-scale capacitance
needs to be connected to the capacitance input, or by writing a
user value to the capacitive gain register. This change would be
only temporary and the factory gain coefficient would be
reloaded back after power-up or reset. The part is tested and
specified only for use with the default factory calibration
coefficient.
CAPACITIVE SYSTEM OFFSET CALIBRATION
The capacitive offset is dominated by the parasitic offset in the
application, such as the initial capacitance of the sensor, any
parasitic capacitance of tracks on the board, and the capacitance
of any other connections between the sensor and the CDC.
Therefore, the AD7745/AD7746 are not factory calibrated for
capacitive offset. It is the user’s responsibility to calibrate the
system capacitance offset in the application.
Any offset in the capacitance input larger than ±1 pF should
first be removed using the on-chip CAPDACs. The small offset
within ±1 pF can then be removed by using the capacitance
offset calibration register.
One method of adjusting the offset is to connect a zero-scale
capacitance to the input and execute the capacitance offset
calibration mode. The calibration sets the midpoint of the
±4.096 pF range (that is, Output Code 0x800000) to that
zero-scale input.
Another method would be to calculate and write the offset cali-
bration register value, the LSB is value 31.25 aF (4.096 pF/2
17
).
The offset calibration register is reloaded by the default value at
power-on or after reset. Therefore, if the offset calibration is not
repeated after each system power-up, the calibration coefficient
value should be stored by the host controller and reloaded as
part of the AD7745/AD7746 setup.
On the AD7746, the register is shared by the two capacitive
channels. If the capacitive channels need to be offset calibrated
individually, the host controller software should read the
AD7746 capacitive offset calibration register values after
performing the offset calibration on individual channels and
then reload the values back to the AD7746 before executing a
conversion on a different channel.
INTERNAL TEMPERATURE SENSOR
INTERNAL TEMPERATURE SENSOR
DIGITAL
FILTER
AND
SCALING
24-BIT
Σ
-
MODULATOR
CLOCK
GENERATOR
0
VOLTAGE
REFERENCE
DATA
I
N
×
I
V
BE
V
DD
Figure 40. Internal Temperature Sensor
The temperature sensing method used in the AD7745/AD7746
is to measure a difference in V
BE
voltage of a transistor
operated at two different currents (see Figure 40). The V
BE
change with temperature is linear and can be expressed as
KT
n
V
f
BE
)
ln(
)
(
N
q
×
=
where:
K
is Boltzmann’s constant (1.38 × 10
–23
).
T
is the absolute temperature in Kelvin.
q
is the charge on the electron (1.6 × 10
–19
coulombs).
N
is the ratio of the two currents.
n
f
is the ideality factor of the thermal diode.
The AD7745/AD7746 uses an on-chip transistor to measure the
temperature of the silicon chip inside the package. The Σ-Δ
ADC converts the V
BE
to digital, the data are scaled using
factory calibration coefficients, thus the output code is
proportional to temperature:
Code
C
e
Temperatur
(
)
4096
2048
=
°
The AD7745/AD7746 has a low power consumption resulting
in only a small effect due to the part self-heating (less than
0.5°C at V
DD
= 5 V).
相關PDF資料
PDF描述
AD7747 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
AD774B Complete 12-Bit A/D Converters(完備的12位A/D轉換器)
AD7750AN Product-to-Frequency Converter
AD7750AR Product-to-Frequency Converter
AD7751(中文) Energy Metering IC with On-Chip Fault Detection(高精度容錯電子能量測量芯片)
相關代理商/技術參數(shù)
參數(shù)描述
AD7747 制造商:AD 制造商全稱:Analog Devices 功能描述:24-Bit Capacitance-to-Digital Converter with Temperature Sensor
AD7747ARUZ 功能描述:IC CONV 24BIT CAP-DGTL 16-TSSOP RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專用型 系列:- 產(chǎn)品培訓模塊:Data Converter Basics 標準包裝:1 系列:- 類型:電機控制 分辨率（位）:12 b 采樣率（每秒）:1M 數(shù)據(jù)接口:串行，并聯(lián) 電壓電源:單電源 電源電壓:2.7 V ~ 3.6 V，4.5 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:100-TQFP 供應商設備封裝:100-TQFP（14x14） 包裝:剪切帶 (CT) 其它名稱:296-18373-1
AD7747ARUZ-REEL 功能描述:IC CONV CAP TO DIG 24BIT 16TSSOP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專用型 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 類型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤 供應商設備封裝:40-TQFN-EP（6x6） 包裝:托盤
AD7747ARUZ-REEL7 功能描述:IC CONV CAP TO DIG 24BIT 16TSSOP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專用型 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 類型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤 供應商設備封裝:40-TQFN-EP（6x6） 包裝:托盤
AD7748BSTZ 制造商:Analog Devices 功能描述:
發(fā)布緊急采購，3分鐘左右您將得到回復。

采購需求

(若只采購一條型號，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進入我的后臺，查看報價

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進入我的后臺，查看報價

*型號 *數(shù)量 廠商 批號 封裝
添加更多采購

我的聯(lián)系方式

*
*
*