參數(shù)資料
型號(hào)： TSC2200
英文描述： PDA ANALOG INTERFACE CIRCUIT
中文描述： 掌上電腦模擬接口電路
文件頁(yè)數(shù)： 9/40頁(yè)
文件大?。?/td> 645K
代理商： TSC2200
9
www.ti.com
TSC2200
SBAS191F
FIGURE 2. 4-Wire Touch Screen Construction.
FIGURE 3. Pressure Measurement.
OPERATION
—
TOUCH SCREEN
A resistive touch screen works by applying a voltage across
a resistor network and measuring the change in resistance at
a given point on the matrix where a screen is touched by an
input stylus, pen, or finger. The change in the resistance ratio
marks the location on the touch screen.
The TSC2200 supports the resistive 4-wire configurations
(see Figure 1). The circuit determines location in two coordi-
nate pair dimensions, although a third dimension can be
added for measuring pressure.
THE 4-WIRE TOUCH SCREEN COORDINATE
PAIR MEASUREMENT
A 4-wire touch screen is constructed as shown in Figure 2.
It consists of two transparent resistive layers separated by
insulating spacers.
The 4-wire touch screen panel works by applying a voltage
across the vertical or horizontal resistive network. The A/D
converter converts the voltage measured at the point the
panel is touched. A measurement of the Y-position of the
pointing device is made by connecting the X+ input to a data
converter chip, turning on the Y+ and Y
–
drivers, and
digitizing the voltage seen at the X+ input. The voltage
measured is determined by the voltage divider developed at
the point of touch. For this measurement, the horizontal
panel resistance in the X+ lead does not affect the conver-
sion due to the high input impedance of the A/D converter.
Voltage is then applied to the other axis, and the A/D
converter converts the voltage representing the X-position on
the screen. This provides the X- and Y-coordinates to the
associated processor.
Measuring touch pressure (Z) can also be done with the
TSC2200. To determine pen or finger touch, the pressure of
the
“
touch
”
needs to be determined. Generally, it is not
necessary to have very high performance for this test, there-
fore, the 8-bit resolution mode is recommended (however,
calculations will be shown with the 12-bit resolution mode).
There are several different ways of performing this measure-
ment. The TSC2200 supports two methods. The first method
requires knowing the X-plate resistance, measurement of the
X-position, and two additional cross panel measurements (Z
2
and Z
1
) of the touch screen, as seen in Figure 3. Using
Equation 1 will calculate the touch resistance:
R
R
X-Position
4096
Z
Z
–
1
TOUCH
X-Plate
2
1
=
(1)
The second method requires knowing both the X-plate and
Y-plate resistance, measurement of X-position and Y-posi-
tion, and Z
1
. Using Equation 2 will also calculate the touch
resistance:
(2)
R
R
X Position
-
4096
Z
R
Y Position
-
4096
TOUCH
X Plate
-
Y Plate
-
=
4096
1
1
1
When the touch panel is pressed or touched, and the drivers
to the panel are turned on, the voltage across the touch panel
will often overshoot and then slowly settle (decay) down to a
stable DC value. This is due to mechanical bouncing which
is caused by vibration of the top layer sheet of the touch
panel when the panel is pressed. This settling time must be
accounted for, or else the converted value will be in error.
Therefore, a delay must be introduced between the time the
driver for a particular measurement is turned on, and the time
measurement is made.
Conductive Bar
Insulating
Material
(Glass)
Silver
Ink
Transparent
Conductor (ITO)
Bottom Side
Transparent
Conductor (ITO)
Top Side
X+
X
–
Y+
Y
–
ITO = Indium Tin Oxide
X-Position
Measure X-Position
Measure Z
1
-Position
Touch
X+
Y+
X
–
Y
–
Z
1
-Position
Touch
X+
Y+
Y
–
X
–
Measure Z
2
-Position
Z
2
-Position
Touch
X+
Y+
Y
–
X
–
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TSC2200IPW 功能描述:觸摸屏轉(zhuǎn)換器和控制器 Prog 4-Wire w/12-Bit 125KHz ADC & Key Ifc RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20
TSC2200IPWG4 功能描述:觸摸屏轉(zhuǎn)換器和控制器 Prog 4-Wire w/12-Bit 125KHz ADC & Key Ifc RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20
TSC2200IPWR 功能描述:觸摸屏轉(zhuǎn)換器和控制器 Prog 4-Wire w/12-Bit 125KHz ADC & Key Ifc RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20
TSC2200IPWRG4 功能描述:觸摸屏轉(zhuǎn)換器和控制器 Prog 4-Wire w/12-Bit 125KHz ADC & Key Ifc RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20
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