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參數資料
| 型號： | AD7142ACPZ-REEL |
| 廠商： | Analog Devices Inc |
| 文件頁數： | 5/73頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC CAP-TO-DGTL CONV PROG 32LFCSP |
| 標準包裝： | 1 |
| 類型： | 電容數字轉換器 |
| 分辨率（位）： | 16 b |
| 采樣率（每秒）： | 250k |
| 數據接口： | 串行 |
| 電壓電源： | 單電源 |
| 電源電壓： | 2.6 V ~ 3.6 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 32-VFQFN 裸露焊盤，CSP |
| 供應商設備封裝： | 32-LFCSP-VQ |
| 包裝： | 標準包裝 |
| 產品目錄頁面： | 781 (CN2011-ZH PDF) |
| 其它名稱： | AD7142ACPZ-REELDKR |
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AD7142
Rev. A | Page 12 of 72
THEORY OF OPERATION
The AD7142 and AD7142-1 are capacitance-to-digital
converters (CDCs) with on-chip environmental compensation,
intended for use in portable systems requiring high resolution
user input. The internal circuitry consists of a 16-bit, ∑-Δ con-
verter that converts a capacitive input signal into a digital value.
There are 14 input pins on the AD7142 and AD7142-1, CIN0 to
CIN13. A switch matrix routes the input signals to the CDC.
The result of each capacitance-to-digital conversion is stored in
on-chip registers. The host subsequently reads the results over
the serial interface. The AD7142 contains an SPI interface and
the AD7142-1 has an I2C interface ensuring that the parts are
compatible with a wide range of host processors. Because the
AD7142 and AD7142-1 are identical parts, with the exception of
the serial interface, AD7142 refers to both the AD7142 and
AD7142-1 throughout this data sheet.
The AD7142 interfaces with up to 14 external capacitance
sensors. These sensors can be arranged as buttons, scroll bars,
wheels, or as a combination of sensor types. The external
sensors consist of electrodes on a single or multiple layer PCB
that interfaces directly to the AD7142.
The AD7142 can be set up to implement any set of input
sensors by programming the on-chip registers. The registers can
also be programmed to control features such as averaging,
offsets, and gains for each of the external sensors. There is a
sequencer on-chip to control how each of the capacitance
inputs is polled.
The AD7142 has on-chip digital logic and 528 words of RAM
that are used for environmental compensation. The effects of
humidity, temperature, and other environmental factors can
effect the operation of capacitance sensors. Transparent to the
user, the AD7142 performs continuous calibration to compen-
sate for these effects, allowing the AD7142 to give error-free
results at all times.
The AD7142 requires some minor companion software that
runs on the host or other microcontroller to implement high
resolution sensor functions such as a scroll bar or wheel.
However, no companion software is required to implement
buttons, including 8-way button functionality. Button sensors
are implemented completely in digital logic on-chip.
The AD7142 can be programmed to operate in either full power
mode, or in low power automatic wake-up mode. The
automatic wake-up mode is particularly suited for portable
devices that require low power operation giving the user
significant power savings coupled with full functionality.
The AD7142 has an interrupt output, INT, to indicate when
new data has been placed into the registers. INT is used to
interrupt the host on sensor activation. The AD7142 operates
from a 2.6 V to 3.6 V supply, and is available in a 32-lead, 5 mm ×
5 mm LFCSP_VQ.
CAPACITANCE SENSING THEORY
The AD7142 uses a method of sensing capacitance known as
the shunt method. Using this method, an excitation source is
connected to a transmitter generating an electric field to a
receiver. The field lines measured at the receiver are translated
into the digital domain by a ∑-Δ converter. When a finger, or
other grounded object, interferes with the electric field, some of
the field lines are shunted to ground and do not reach the
receiver (see Figure 18). Therefore, the total capacitance
measured at the receiver decreases when an object comes close
to the induced field.
EXCITATION
SIGNAL
250kHz
Σ-Δ
ADC
16-BIT
DATA
05
70
2-
0
07
PLASTIC COVER
AD7142
Tx
Rx
PCB LAYER 1
Figure 18. Sensing Capacitance Method
In practice, the excitation source and ∑-Δ ADC are implemented
on the AD7142, and the transmitter and receiver are constructed
on a PCB that makes up the external sensor.
Registering a Sensor Activation
When a sensor is approached, the total capacitance associated
with that sensor, measured by the AD7142, changes. When the
capacitance changes to such an extent that a set threshold is
exceeded, the AD7142 registers this as a sensor touch.
Preprogrammed threshold levels are used to determine if a
change in capacitance is due to a button being activated. If the
capacitance exceeds one of the threshold limits, the AD7142
registers this as a true button activation. The same thresholds
principle is used to determine if other types of sensors, such as
sliders or scroll wheels, are activated.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7142ACPZ-REEL1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Programmable Controller for Capacitance Touch Sensors |
| AD7143 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Programmable Controller for Capacitance Touch Sensors |
| AD7143ACPZ | 制造商:Analog Devices 功能描述:IC CDC 16BIT SMD LFCSP-16 7143 制造商:Analog Devices 功能描述:IC, CDC, 16BIT, SMD, LFCSP-16, 7143 |
| AD7143ACPZ-1500RL7 | 功能描述:IC CTLR PROGRAMMABLE CDC 16LFCSP RoHS:是 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關文件:Automotive Product Guide 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數字 輸出類型:數字 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） 供應商設備封裝:20-TSSOP 包裝:管件 |
| AD7143ACPZ-1REEL | 功能描述:IC CONV CAP-TO-DGTL PROG 16LFCSP RoHS:是 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關文件:Automotive Product Guide 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數字 輸出類型:數字 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） 供應商設備封裝:20-TSSOP 包裝:管件 |
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