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參數(shù)資料
| 型號： | MXB7843EEE |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | ADC |
| 英文描述： | 2.375V to 5.25V, 4-Wire Touch-Screen |
| 中文描述： | 2-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO16 |
| 封裝： | 0.150 INCH, 0.025 INCH PITCH, MO-137AB, QSOP-16 |
| 文件頁數(shù)： | 10/21頁 |
| 文件大?。?/td> | 508K |
| 代理商： | MXB7843EEE |
M
Analog Input Protection
Internal protection diodes, which clamp the analog
input to V
DD
and GND, allow the analog input pins to
swing from GND - 0.3V to V
DD
+ 0.3V without damage.
Analog inputs must not exceed V
DD
by more than
50mV or be lower than GND by more than 50mV for
accurate conversions. If an off-channel analog input
voltage exceeds the supplies, limit the input current to
50mA. The analog input pins are ESD protected to
±8kV using the Contact-Discharge method and ±15kV
using the Air-Gap method specified in IEC 61000-4-2.
Touch-Screen Conversion
The MXB7843 provides two conversion methods
—
dif-
ferential and single ended. The SER/
DFR
bit in the con-
trol word selects either mode. A logic 1 selects a
single-ended conversion, while a logic 0 selects a dif-
ferential conversion.
Differential vs. Single Ended
Changes in operating conditions can degrade the accu-
racy and repeatability of touch-screen measurements.
Therefore, the conversion results representing X and Y
coordinates may be incorrect. For example, in single-
ended measurement mode, variation in the touch-
screen driver voltage drops results in incorrect input
reading. Differential mode minimizes these errors.
Single-Ended Mode
Figure 3 shows the switching matrix configuration for
Y-coordinate measurement in single-ended mode. The
MXB7843 measures the position of the pointing device by
connecting X+ to IN+ of the ADC, enabling Y+ and Y- dri-
vers, and digitizing the voltage on X+. The ADC performs
a conversion with REF+ = REF and REF- = GND. In sin-
gle-ended measurement mode, the bias to the touch
screen can be turned off after the acquisition to save
power. The on-resistance of the X and Y drivers results in
a gain error in single-ended measurement mode. Touch-
screen resistance ranges from 200
to 900
(depending
on the manufacturer), whereas the on-resistance of the X
and Y drivers is 8
(typ). Limit the touch-screen current to
less than 50mA by using a touch screen with a resistance
higher than 100
. The resistive divider created by the
touch screen and the on-resistance of the X and Y drivers
result in both an offset and a gain shift. Also, the on-resis-
tance of the X and Y drivers does not track the resistance
of the touch screen over temperature and supply. This
results in further measurement errors.
Differential Measurement Mode
Figure 4 shows the switching matrix configuration for
Y-coordinate measurement. The REF+ and REF- inputs
are connected directly to the Y+ and Y- pins, respec-
tively. Differential mode uses the voltage at the Y+ pin
as the REF+ voltage and voltage at the Y- pin as REF-
voltage. This conversion is ratiometric and independent
of the voltage drop across the drivers and variation in
the touch-screen resistance. In differential mode, the
touch screen remains biased during the acquisition and
conversion process. This results in additional supply
current and power dissipation during conversion when
compared to the absolute measurement mode.
PEN Interrupt Request (
PENIRQ
)
Figure 5 shows the block diagram for the
PENIRQ
func-
tion. When used,
PENIRQ
requires a 10k
to 100k
pullup to +V
DD
. If enabled,
PENIRQ
goes low whenever
the touch screen is touched. The
PENIRQ
output can
be used to initiate an interrupt to the microprocessor,
which can write a control word to the MXB7843 to start
a conversion.
Figure 6 shows the timing diagram for the
PENIRQ
pin
function. The diagram shows that once the screen is
touched while
CS
is high, the
PENIRQ
output goes low
after a time period indicated by t
TOUCH
. The t
TOUCH
value changes for different touch-screen parasitic
capacitance and resistance. The microprocessor
receives this interrupt and pulls
CS
low to initiate a con-
version. At this instant, the
PENIRQ
pin should be
masked, as transitions can occur due to a selected
input channel or the conversion mode. The
PENIRQ
pin
functionality becomes valid when either the last data bit
is clocked out, or
CS
is pulled high.
External Reference
During conversion, an external reference at REF must
deliver up to 40μA DC load current. If the reference has
a higher output impedance or is noisy, bypass it close
to the REF pin with a 0.1μF and a 4.7μF capacitor.
2.375V to 5.25V, 4-Wire Touch-Screen
Controller
10
______________________________________________________________________________________
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MXB7843EUE | 2.375V to 5.25V, 4-Wire Touch-Screen |
| MXD1000SE__ | 5-Tap Silicon Delay Line |
| MXD1000PA__ | 5-Tap Silicon Delay Line |
| MXD1000PD__ | 5-Tap Silicon Delay Line |
| MXD1000SA__ | 5-Tap Silicon Delay Line |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MXB7843EEE+ | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 2.375-5.25V 4-Wire Touch-Screen Ctlr 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 |
| MXB7843EEE+T | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 2.375-5.25V 4-Wire Touch-Screen Ctlr 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 |
| MXB7843EEE-T | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 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 |
| MXB7843EUE | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 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 |
| MXB7843EUE+ | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 2.375-5.25V 4-Wire Touch-Screen Ctlr 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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