參數(shù)資料
型號(hào)： WM9712LEFL
廠商： Wolfson Microelectronics
元件分類： Codec
英文描述： AC97 Audio and Touchpanel CODEC
中文描述： AC97音頻編解碼器和觸摸屏
文件頁(yè)數(shù)： 39/78頁(yè)
文件大小： 689K
代理商： WM9712LEFL
Production Data
WM9712L
w
PD Rev 4.0 December 2003
39
The principle of operation is illustrated below (Note: the illustrations assume that the top plate is used
for X and the bottom plate for Y measurements, although the reverse is also possible).
Y+ (15)
X+
(14)
Y- (17)
X- (16)
R
X+
R
Y-
pen / finger
R
Y+
R
X-
V
M
= (V
- V
) R
/ (R
+ R
X+
)
= proportional to X position
ADC
V
REF+
V
REF-
TPVDD
TPGND
WM9712
VM
Figure 6 X Co-ordinate Measurement on 4-wire Touchpanel
For an X co-ordinate measurement, the X+ pin is internally switched to VDD and X- to GND. The X
plate becomes a potential divider, and the voltage at the point of contact is proportional to its X co-
ordinate. This voltage is measured on the Y+ and Y- pins, which carry no current (hence there is no
voltage drop in R
Y+
or R
Y-
).
Due to the ratiometric measurement method, the supply voltage does not affect measurement
accuracy. The voltage references VREF+ and VREF- are taken from after the matrix switches, so
that any voltage drop in these switches has no effect on the ADC measurement.
Y+ (15)
X+
(14)
Y- (17)
X- (16)
R
X+
R
Y-
pen / finger
R
Y+
R
X-
V
M
= (V
- V
) R
/ (R
+ R
Y+
)
= proportional to Y position
ADC
V
REF+
V
REF-
TPVDD
TPGND
WM9712
VM
Figure 7 Y Co-ordinate Measurement on 4-wire Touchpanel
Y co-ordinate measurements are similar to X co-ordinate measurements, with the X and Y plates
interchanged.
zero power
comparator
Y+ (15)
X+
(14)
Y- (17)
X- (16)
R
X+
R
Y-
pen / finger
R
Y+
R
X-
TPGND
WM9712
PEN
DOWN
TPVDD
R
PU
Figure 8 Pen Down Detection on 4-wire Touchpanel
Pen down detection uses a zero power comparator (effectively a CMOS logic gate) with an internal,
programmable pull-up resistor R
PU
that controls pen-down sensitivity. Increasing R
PU
makes the
touchpanel less sensitive to touch, while lowering R
PU
makes it more sensitive.
相關(guān)PDF資料
PDF描述
WM9712LEFT AC97 Audio and Touchpanel CODEC
WM9712LEFV AC97 Audio and Touchpanel CODEC
WM9712LSEFL AC97 Audio and Touchpanel CODEC
WM9712LSEFT AC97 Audio and Touchpanel CODEC
WM9712LSEFV AC97 Audio and Touchpanel CODEC
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
WM9712LEFL/RV 制造商:WOLFSON 制造商全稱:WOLFSON 功能描述:AC97 Audio and Touchpanel CODEC
WM9712LEFL/V 制造商:WOLFSON 制造商全稱:WOLFSON 功能描述:AC97 Audio and Touchpanel CODEC
WM9712LEFT 制造商:WOLFSON 制造商全稱:WOLFSON 功能描述:AC97 Audio and Touchpanel CODEC
WM9712LEFT/RV 制造商:WOLFSON 制造商全稱:WOLFSON 功能描述:AC97 Audio and Touchpanel CODEC
WM9712LEFV 制造商:WOLFSON 制造商全稱:WOLFSON 功能描述:AC97 Audio and Touchpanel CODEC
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