- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385644 > MXB7846EUE (MAXIM INTEGRATED PRODUCTS INC) 2.375V to 5.25V, 4-Wire Touch-Screen Controller with Internal Reference and Temperature Sensor PDF資料下載
參數(shù)資料
| 型號： | MXB7846EUE |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | ADC |
| 英文描述： | 2.375V to 5.25V, 4-Wire Touch-Screen Controller with Internal Reference and Temperature Sensor |
| 中文描述： | 2-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO16 |
| 封裝： | 4.40 MM, 0.65 MM PITCH, MO-153AC, TSSOP-16 |
| 文件頁數(shù)： | 11/23頁 |
| 文件大?。?/td> | 967K |
| 代理商： | MXB7846EUE |
M
2.375V to 5.25V, 4-Wire Touch-Screen Controller
with Internal Reference and Temperature Sensor
______________________________________________________________________________________
11
Input Bandwidth and Anti-Aliasing
The ADCs input tracking circuitry has a 25MHz small-
signal bandwidth, so it is possible to digitize high-
speed transient events. To avoid high-frequency sig-
nals being aliased into the frequency band of interest,
anti-alias filtering is recommended.
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 con-
version. 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 MXB7846 provides two conversion methods—differ-
ential and single ended. The SER/
DFR
bit in the control
word selects either mode. A logic 1 selects a single-
ended conversion, while a logic 0 selects a differential
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
MXB7846 measures the position of the pointing device
by connecting X+ to IN+ of the ADC, enabling Y+ and
Y- drivers, and digitizing the voltage on X+. The ADC
performs a conversion with REF+ = REF and REF- =
GND. In single-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-resistance of the X
and Y drivers does not track the resistance of the touch
screen over temperature and supply. This results in fur-
ther 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 MXB7846 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.
Touch-Pressure Measurement
The MXB7846 provides two methods for measuring the
pressure applied to the touch screen (Figure 7). By
measuring R
TOUCH
, it is possible to differentiate
between a finger or stylus in contact with the touch
screen. Although 8-bit resolution is typically sufficient,
the following calculations use 12-bit resolution demon-
strating the maximum precision of the MXB7846.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MXD1005PA__ | 5-Tap Silicon Delay Line |
| MXD1005PD__ | 5-Tap Silicon Delay Line |
| MXD1005SA__ | 5-Tap Silicon Delay Line |
| MXD1005SE__ | 5-Tap Silicon Delay Line |
| MXD1005UA__ | 5-Tap Silicon Delay Line |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MXB7846EUE+ | 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 |
| MXB7846EUE+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 |
| MXB7846EUE-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 |
| MXB7846EVC16 | 功能描述:數(shù)據(jù)轉(zhuǎn)換 IC 開發(fā)工具 MXB7846C16 Eval Kit RoHS:否 制造商:Texas Instruments 產(chǎn)品:Demonstration Kits 類型:ADC 工具用于評估:ADS130E08 接口類型:SPI 工作電源電壓:- 6 V to + 6 V |
| MXB7846EVKIT | 功能描述:開發(fā)板和工具包 - 其他處理器 Programmers, Development Systems RoHS:否 制造商:Freescale Semiconductor 產(chǎn)品:Development Systems 工具用于評估:P3041 核心:e500mc 接口類型:I2C, SPI, USB 工作電源電壓: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。