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參數(shù)資料
| 型號： | AD7873BCP |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 消費(fèi)家電 |
| 英文描述： | Touch Screen Digitizer |
| 中文描述： | SPECIALTY CONSUMER CIRCUIT, QCC16 |
| 封裝： | 4 X 4 MM, MO-220VGGC, LFCSP-16 |
| 文件頁數(shù)： | 18/28頁 |
| 文件大小： | 657K |
| 代理商： | AD7873BCP |
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AD7873
PEN INTERRUPT REQUEST
The pen interrupt equivalent circuitry is outlined in Figure 33.
By connecting a pull-up resistor (10 k to 100 k) between +V
CC
and this CMOS logic open drain output, the PENIRQ output
remains high normally. If PENIRQ is enabled (see Table 7), when
the touch screen connected to the AD7873 is touched by a pen
or finger, the PENIRQ output goes low, initiating an interrupt to
a microprocessor, which can then instruct a control word to be
written to the AD7873 to initiate a conversion. This output can
also be enabled between conversions during power-down (see
Table 7) allowing power-up to be initiated only when the screen
is touched. The result of the first touch screen coordinate con-
version after power-up is valid, assuming any external reference
is settled to the 12-bit or 8-bit level as required.
Rev. D | Page 18 of 28
Figure 34 assumes that the PENIRQ function was enabled in
the last write or that the part was just powered up so PENIRQ is
enabled by default. Once the screen is touched, the PENIRQ
output goes low a time t
PEN
later. This delay is approximately
5 μs, assuming a 10 nF touch screen capacitance, and varies with
the touch screen resistance actually used. Once the START bit is
detected, the pen interrupt function is disabled and the PENIRQ
cannot respond to screen touches. The PENIRQ output remains
low until the fourth falling edge of DCLK after the START bit is
clocked in, at which point it returns high as soon as possible,
irrespective of the touch screen capacitance. This does not mean
that the pen interrupt function is now enabled again because
the power-down bits have not yet been loaded to the control
register. Regardless of whether PENIRQ is to be enabled again,
the PENIRQ output normally always idles high . Assuming the
PENIRQ is enabled again as shown in Figure 34, then once the
conversion is complete, the PENIRQ output again responds to a
screen touch. The fact that PENIRQ returns high almost
immediately after the fourth falling edge of DCLK means the
user avoids any spurious interrupts on the microprocessor or
DSP, which could occur if the interrupt request line on the
micro/DSP were unmasked during or toward the end of
conversion and the PENIRQ pin was still low. Once the next
START bit is detected by the AD7843, the PENIRQ function is
again disabled.
If the control register write operation overlaps with the data
read, a START bit is always detected prior to the end of
conversion, meaning that even if the PENIRQ function is
enabled in the control register, it is disabled by the START bit
again before the end of the conversion is reached, so the
PENIRQ function effectively cannot be used in this mode.
However, as conversions are occurring continuously, the
PENIRQ function is not necessary and is therefore redundant.
0
Y+
Y–
ON
X+
TOUCH
SCREEN
EXTERNAL
PULL-UP
PENIRQ
ENABLE
+V
CC
+V
CC
PENIRQ
100k
Figure 33. PENIRQ Functional Block Diagram
0
S
A2
A1
A0
1
0
8
1
1
13
16
MODEDFR
SCREEN
TOUCHED
HERE
INTERRUPT
PROCESSOR
NO RESPONSE TO TOUCH
t
PEN
PENIRQ
CS
DCLK
DIN
(START)
PD1 = 1, PD0 = 0, PENIRQ
ENABLED AGAIN
Figure 34. PENIRQ Timing Diagram
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD7873BRQ | Touch Screen Digitizer |
| AD7874 | 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System(LC2MOS 4通道,12位同時采樣DAS) |
| AD7878SQ | IC 1:10 CLOCK DRIVER 20-QSOP |
| AD7878 | LC2MOS Complete 12-Bit 100 kHz Sampling ADC with DSP Interface |
| AD7878AQ | LC2MOS Complete 12-Bit 100 kHz Sampling ADC with DSP Interface |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7873BCP-REEL | 制造商:Analog Devices 功能描述:TOUCH SCREEN DIGITIZER |
| AD7873BCP-REEL7 | 制造商:Analog Devices 功能描述:TOUCH SCREEN DIGITIZER 制造商:Analog Devices 功能描述:2.7V 12-BIT TOUCH SCREEN DIGITIZER I.C. - Tape and Reel |
| AD7873BCPZ | 制造商:Analog Devices 功能描述:TOUCH SCREEN DIGITIZER |
| AD7873BRQ | 制造商:Analog Devices 功能描述:TOUCH SCREEN DIGITIZER |
| AD7873BRQ-REEL | 制造商:Analog Devices 功能描述:TOUCH SCREEN DIGITIZER |
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