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參數(shù)資料
| 型號： | TSC2003IZQCT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | ADC |
| 英文描述： | 2-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PBGA48 |
| 封裝： | PLASTIC, VFBGA-48 |
| 文件頁數(shù)： | 11/25頁 |
| 文件大?。?/td> | 535K |
| 代理商： | TSC2003IZQCT |
TSC2003
19
SBAS162G
www.ti.com
PENIRQ output is HIGH. While in the power-down mode, with
PD0 = 0, the Y– driver is ON and connected to GND, and the
PENIRQ output is connected to the X+ input. When the panel
is touched, the X+ input is pulled to ground through the touch
screen, and PENIRQ output goes LOW due to the current path
through the panel to GND, initiating an interrupt to the processor.
During the measurement cycle for X-, Y-, and Z-Position, the X+
input will be disconnected from the PENIRQ pull-down transis-
tor to eliminate any leakage current from the pull-up resistor to
flow through the touch screen, thus causing no errors.
In addition to the measurement cycles for X-, Y-, and Z-
position, commands which activate the X-drivers, Y-drivers, Y+
and X-drivers without performing a measurement also discon-
nect the X+ input from the PENIRQ pull-down transistor and
disable the pen-interrupt output function regardless of the value
of the PD0 bit. Under these conditions, the PENIRQ output will
be forced LOW. Furthermore, if the last command byte written
to the TSC2003 contains PD0 = 1, the pen-interrupt output
function will be disabled and will not be able to detect when the
panel is touched. In order to re-enable the pen-interrupt output
function under these circumstances, a command byte needs to
be written to the TSC2003 with PD0 = 0.
Once the bus master sends the address byte with R/W = 0
(see Figure 10) and the TSC2003 sends an acknowledge,
the pen-interrupt function is disabled. If the command which
follows the address byte has PD0 = 0, then the pen-interrupt
function will be enabled at the end of a conversion. This is
approximately 10
s (12-bit mode) or 7s (8-bit mode) after
the TSC2003 receives a STOP/START condition following
the reception of a command byte (see Figures 12 and 14 for
further details of when the conversion cycle begins).
In both cases listed above, it is recommended that the
master processor mask the interrupt which the PENIRQ is
associated with whenever the host writes to the TSC2003.
This will prevent false triggering of interrupts when the
PENIRQ line is disabled in the cases listed above.
For optimum performance, care should be taken with the
physical layout of the TSC2003 circuitry. The basic SAR archi-
tecture is sensitive to glitches or sudden changes on the power
supply, reference, ground connections, and digital inputs that
occur just prior to latching the output of the analog comparator.
Therefore, during any single conversion for an n-bit SAR
converter, there are n “windows” in which large external tran-
sient voltages can easily affect the conversion result. Such
glitches might originate from switching power supplies, nearby
digital logic, and high-power devices. The degree of error in the
digital output depends on the reference voltage, layout, and the
exact timing of the external event. The error can change if the
external event changes in time with respect to the SCL input.
With this in mind, power to the TSC2003 should be clean and
well bypassed. A 0.1
F ceramic bypass capacitor should be
placed as close to the device as possible. In addition, a 1
F
to 10
F capacitor may also be needed if the impedance of
the connection between +VDD and the power supply is high.
A bypass capacitor is generally not needed on the VREF pin
because the internal reference is buffered by an internal op
amp. If an external reference voltage originates from an op
amp, make sure that it can drive any bypass capacitor that
is used without oscillation.
The TSC2003 architecture offers no inherent rejection of noise
or voltage variation in regards to using an external reference
input. This is of particular concern when the reference input is
tied to the power supply. Any noise and ripple from the supply
will appear directly in the digital results. While high-frequency
noise can be filtered out, voltage variation due to line fre-
quency (50Hz or 60Hz) can be difficult to remove.
The GND pin should be connected to a clean ground point. In
many cases, this will be the “analog” ground. Avoid connec-
tions which are too near the grounding point of a microcontroller
or digital signal processor. If needed, run a ground trace
directly from the converter to the power-supply entry point. The
ideal layout will include an analog ground plane dedicated to
the converter and associated analog circuitry.
In the specific case of use with a resistive touch screen, care
should be taken with the connection between the converter
and the touch screen. Since resistive touch screens have
fairly low resistance, the interconnection should be as short
and robust as possible. Longer connections will be a source
of error, much like the on-resistance of the internal switches.
Likewise, loose connections can be a source of error when
the contact resistance changes with flexing or vibrations.
As indicated previously, noise can be a major source of error in
touch screen applications (e.g., applications that require a backlit
LCD panel). This EMI noise can be coupled through the LCD panel
to the touch screen and cause “flickering” of the converted data.
Several things can be done to reduce this error, such as utilizing a
touch screen with a bottom-side metal layer connected to ground.
This will couple the majority of noise to ground. Additionally, filtering
capacitors from Y+, Y–, X+, and X– to ground can also help.
PENIRQ
OUTPUT
The pen-interrupt output function is shown in Figure 16. By
connecting a pull-up resistor to VDD (typically 100k), the
PENIRQ
V
DD
10k
30k
to 100k
ON
Y+ or X+ drivers on,
or TEMP0, TEMP1
measurements activated
Y+
X+
Y–
TEMP0
TEMP1
TEMP
DIODE
HIGH except
when TEMP0,
TEMP1 activated
V
DD
V
DD
FIGURE 16. PENIRQ Functional Block Diagram.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TSC2003-Q1 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:I2C TOUCH SCREEN CONTROLLER |
| TSC2004 | 制造商:BB 制造商全稱:BB 功能描述:1.2V to 3.6V, 12-Bit, Nanopower, 4-Wire TOUCH SCREEN CONTROLLER with I2C⑩ Interface |
| TSC2004_12 | 制造商:BB 制造商全稱:BB 功能描述:1.2V to 3.6V, 12-Bit, Nanopower, 4-Wire |
| TSC2004EVM | 功能描述:觸摸傳感器開發(fā)工具 TSC2004EVM Eval Mod RoHS:否 制造商:Cypress Semiconductor 工具用于評估: 接口類型: 工作電壓: 最大工作溫度: |
| TSC2004EVM-PDK | 功能描述:觸摸傳感器開發(fā)工具 TSC2004EVM-PDK Eval Mod RoHS:否 制造商:Cypress Semiconductor 工具用于評估: 接口類型: 工作電壓: 最大工作溫度: |
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