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參數(shù)資料
| 型號： | AD7877 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Touch Screen Controller |
| 中文描述： | 觸摸屏控制器 |
| 文件頁數(shù)： | 14/44頁 |
| 文件大?。?/td> | 1002K |
| 代理商： | AD7877 |
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AD7877
CIRCUIT INFORMATION
The AD7877 is a complete, 12-bit data acquisition system for
digitizing positional inputs from a touch screen in PDAs and
other devices. In addition, it can monitor two battery voltages,
ambient temperature, and three auxiliary analog voltages, with
high and low limit comparisons on three of the inputs, and has
up to four general-purpose logic I/O pins.
Rev. A | Page 14 of 44
The core of the AD7877 is a high speed, low power, 12-bit
analog-to-digital converter (ADC) with input multiplexer,
on-chip track-and-hold, and on-chip clock. The results of
conversions are stored in 11 results registers, and the results
from one auxiliary input and two battery inputs can be
compared with high and low limits stored in limit registers to
generate an out-of-limit ALERT. The AD7877 also contains low
resistance analog switches to switch the X and Y excitation
voltages to the touch screen, a STOPACQ pin to control the
ADC acquisition period, 2.5 V reference, on-chip temperature
sensor, and 8-bit DAC to control LCD contrast. The high speed
SPI serial bus provides control of, and communication with, the
device.
Operating from a single supply from 2.2 V to 5 V, the AD7877
offers throughput rates of up to 125 kHz. The device is available
in a 5 mm by 5 mm 32-lead lead frame chip scale package.
The data acquisition system of the AD7877 has a number of
advanced features:
Input channel sequenced automatically or selected by
the host
STOPACQ feature to reduce noise from LCD
Averaging of from 1 to 16 conversions for noise
reduction
Programmable acquisition time
Power management
Programmable ADC power-up delay before first
conversion
Choice of internal or external reference
Conversion at preprogrammed intervals
TOUCH SCREEN PRINCIPLES
A 4-wire touch screen consists of two flexible, transparent,
resistive-coated layers that are normally separated by a small air
gap. The X layer has conductive electrodes running down the
left and right edges, allowing the application of an excitation
voltage across the X layer from left to right.
0
X+
X–
Y–
Y+
CONDUCTIVE ELECTRODE
ON BOTTOM SIDE
PLASTIC FILM WITH
TRANSPARENT, RESISTIVE
COATING ON BOTTOM SIDE
PLASTIC FILM WITH
TRANSPARENT, RESISTIVE
COATING ON TOP SIDE
LCD SCREEN
CONDUCTIVE ELECTRODE
ON TOP SIDE
Figure 26. Basic Construction of a Touch Screen
The Y layer has conductive electrodes running along the top
and bottom edges, allowing the application of an excitation
voltage down the layer from top to bottom.
Provided that the layers are of uniform resistivity, the voltage at
any point between the two electrodes is proportional to the
horizontal position for the X layer and the vertical position for
the Y layer.
When the screen is touched, the two layers make contact. If only
the X layer is excited, the voltage at the point of contact, and
therefore the horizontal position, can be sensed at one of the
Y layer electrodes. Similarly, if only the Y layer is excited, the
voltage, and therefore the vertical position, can be sensed at one
of the X electrodes. By switching alternately between X and
Y excitation and measuring the voltages, the X and Y coordi-
nates of the contact point can be found.
In addition to measuring the X and Y coordinates, it is also
possible to estimate the touch pressure by measuring the
contact resistance between the X and Y layers. The AD7877 is
designed to facilitate this measurement.
Figure 28 shows an equivalent circuit of the analog input
structure of the AD7877, showing the touch screen switches, the
main analog multiplexer, the ADC with analog and differential
reference inputs, and the dual 3-to-1 multiplexer that selects the
reference source for the ADC.
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| AD7877ACP-500RL7 | Touch Screen Controller |
| AD7877ACP-REEL | Touch Screen Controller |
| AD7877ACP-REEL7 | Touch Screen Controller |
| AD7877ACPZ-500RL7 | Touch Screen Controller |
| AD7877ACPZ-REEL | Touch Screen Controller |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AD7877AACPZ-500RL7 | 制造商:Analog Devices 功能描述: |
| AD7877AACPZ-REEL7 | 制造商:Analog Devices 功能描述: |
| AD7877ACBZ-REEL | 功能描述:IC CTRLR TOUCH SCREEN 25-WLCSP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 觸摸屏控制器 系列:- 標準包裝: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:- 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） 供應商設備封裝:16-TSSOP 包裝:帶卷 (TR) |
| AD7877ACBZ-REEL7 | 功能描述:IC CTRLR TOUCH SCREEN 25-WLCSP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 觸摸屏控制器 系列:- 標準包裝: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:- 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） 供應商設備封裝:16-TSSOP 包裝:帶卷 (TR) |
| AD7877ACP | 制造商:Analog Devices 功能描述:TOUCH SCREEN CNTRLR 32LFCSP - Bulk |
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