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參數(shù)資料
| 型號： | AD7148ACPZ-1500RL7 |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 16/57頁 |
| 文件大小： | 0K |
| 描述： | IC CAP-TO-DGTL CONV PROG 16LFCSP |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 類型： | 電容性 |
| 觸摸面板接口： | 2 線 |
| 輸入數(shù)/鍵： | 8 鍵 |
| 分辨率（位）： | 16 b |
| 數(shù)據(jù)接口： | I²C，串行 |
| 數(shù)據(jù)速率/采樣率 (SPS，BPS)： | 250k |
| 電壓基準(zhǔn)： | 內(nèi)部 |
| 電源電壓： | 2.6 V ~ 3.3 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 16-VQFN 裸露焊盤，CSP |
| 供應(yīng)商設(shè)備封裝： | 16-LFCSP |
| 包裝： | 標(biāo)準(zhǔn)包裝 |
| 產(chǎn)品目錄頁面： | 781 (CN2011-ZH PDF) |
| 其它名稱： | AD7148ACPZ-1500RL7DKR |
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AD7148
Rev. A | Page 22 of 56
ENVIRONMENTAL CALIBRATION
CAPACITANCE SENSOR BEHAVIOR WITHOUT
CALIBRATION
The AD7148 provides on-chip capacitance sensor calibration
to automatically adjust for environmental conditions that have
an effect on the capacitance sensor ambient levels. Capacitance
sensor output levels are sensitive to temperature, humidity, and
in some cases, dirt. The AD7148 achieves optimal and reliable
sensor performance by continuously monitoring the CDC ambient
levels and correcting for any changes by adjusting the STAGEx_
HIGH_THRESHOLD and STAGEx_LOW_THRESHOLD register
values, as described in Equation 1 and Equation 2. The CDC
ambient level is defined as the capacitance sensor output level
during periods when the user is not approaching or in contact
with the sensor.
Figure 32 shows the typical behavior of a capacitance sensor with
no applied calibration. This figure shows ambient levels drifting
over time as environmental conditions change. The ambient level
drift results in the detection of a missed user contact on Sensor 2.
This is a result of the initial low offset level remaining constant
while the ambient levels drifted upward beyond the detection
range.
The compensation logic runs automatically on every conversion
after configuration when the AD7148 is not being touched, which
allows the AD7148 to account for rapidly changing environmental
conditions.
The ambient compensation control registers give the host access
to general setup and controls for the compensation algorithm.
On-chip RAM stores the compensation data for each conversion
stage, as well as setup information specific to each stage.
Figure 31 shows an example of an ideal capacitance sensor
behavior where the CDC ambient level remains constant,
regardless of the environmental conditions. The CDC output
shown is for a pair of differential button sensors, where one
sensor caused an increase and the other caused a decrease in
measured capacitance when activated. The positive and negative
sensor threshold levels are calculated as a percentage of the
STAGEx_OFFSET_HIGH and STAGEx_OFFSET_LOW values
based on the threshold sensitivity settings and the ambient value.
These values are sufficient to detect a sensor contact, resulting
in the AD7148 asserting the INT output when threshold levels
are exceeded.
CD
C
O
U
T
P
UT
CO
DE
S
STAGEx_LOW_THRESHOLD
STAGEx_HIGH_THRESHOLD
CDC AMBIENT VALUE
t
CHANGING ENVIRONMENTAL CONDITIONS
0
715
5-
0
30
SENSOR 1 INT
ASSERTED
SENSOR 2 INT
ASSERTED
Figure 31. Ideal Sensor Behavior with a Constant Ambient Level
07
15
5-
0
31
CDC
O
U
T
P
UT
CO
DE
S
t
CDC AMBIENT
VALUE DRIFTING
SENSOR 1 INT
ASSERTED
SENSOR 2 INT
NOT ASSERTED
CHANGING ENVIRONMENTAL CONDITIONS
STAGEx_HIGH_THRESHOLD
STAGEx_LOW_THRESHOLD
Figure 32. Typical Sensor Behavior Without Calibration Applied
The Capacitance Sensor Behavior with Calibration section
describes how the AD7148 adaptive calibration algorithm
prevents errors such as this from occurring.
CAPACITANCE SENSOR BEHAVIOR WITH
CALIBRATION
The AD7148 on-chip adaptive calibration algorithm prevents
sensor detection errors such as the one shown in Figure 32.
Error prevention is accomplished by monitoring CDC ambient
levels and readjusting the initial STAGEx_OFFSET_HIGH and
STAGEx_OFFSET_LOW values according to the amount of
ambient drift measured on each sensor. The internal STAGEx_
HIGH_THRESHOLD and STAGEx_LOW_THRESHOLD
values described in Equation 1 and Equation 2 are automatically
updated based on the new values of STAGEx_OFFSET_HIGH
and STAGEx_OFFSET_LOW. This closed-loop routine ensures
the reliability and repeatable operation of every sensor
connected to the AD7148 under dynamic environmental
conditions. Figure 33 shows a simplified example of how the
AD7148 applies the adaptive calibration process resulting in no
interrupt errors under changing CDC ambient levels due to
environmental conditions.
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| AD7148ACPZ-1REEL | 功能描述:IC CAP-TO-DGTL CONV PROG 16LFCSP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 觸摸屏控制器 系列:- 標(biāo)準(zhǔn)包裝:96 系列:- 類型:- 觸摸面板接口:- 輸入數(shù)/鍵:- 分辨率（位）:- 評估套件:* 數(shù)據(jù)接口:- 數(shù)據(jù)速率/采樣率 (SPS，BPS):- 電壓基準(zhǔn):- 電源電壓:- 電流 - 電源:- 工作溫度:- 安裝類型:表面貼裝 封裝/外殼:16-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:16-TSSOP 包裝:帶卷 (TR) |
| AD7150 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Ultra Low Power, 2 Channel, Capacitance Converter for Proximity Sensing |
| AD7150BRMZ | 功能描述:IC CAP CONV 2CH ULT LP 10MSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關(guān)文件:Automotive Product Guide 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數(shù)字 輸出類型:數(shù)字 接口:JTAG，串行 電流 - 電源:100µA 安裝類型:表面貼裝 封裝/外殼:20-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:20-TSSOP 包裝:管件 |
| AD7150BRMZ-REEL | 功能描述:IC CAP CONV 2CH ULT LP 10MSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關(guān)文件:Automotive Product Guide 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數(shù)字 輸出類型:數(shù)字 接口:JTAG，串行 電流 - 電源:100µA 安裝類型:表面貼裝 封裝/外殼:20-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:20-TSSOP 包裝:管件 |
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