MAX11803 Maxim Integrated Products, MAX11803 Datasheet - Page 19

• Manufacturer Part Number: MAX11803
• Description: (MAX11800 - MAX11803) Ultra-Small Resistive Touch-Screen Controllers
• Manufacturer: Maxim Integrated Products

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Z1 and Z2 measurements determine the resistance
between the two planes within the panel sensor during
a touch (R
properties of the panel, one of two equations extract the
value of R
sure and area of the touch applied to the panel. Allow
adequate time for the panel to settle when switching
between position and pressure measurements. Figure 5
shows the physical setup of the panel when performing
pressure measurements.
Z1 and Z2 measurements allow observation of the volt-
age on either side of the effective R
With both Z1 and Z2 measurements available, compute
R
Figure 4. Position Measurements
Table 2. Operating Modes, Conditions, and Options
1
2
3
Low-Power, Ultra-Small Resistive Touch-Screen
OPERATION
MAX11800–
In ACM, the choices are limited to X and Y scan, or X and Y and Z1 scan, or X and Y and Z1 and Z2 scan.
In DCM, each ADC conversion is tagged with MTAG and ETAG only when the continuous bit is set (CONT = 1). DCM does not use
A separate configuration register for delay time, sampling time, averaging, and ADC resolution settings configures the AUX input.
MAX11800/
TOUCH
MAX11803
MAX11801
the FIFO and, therefore, the AP should request the data at the end of the conversion cycle.
PANEL
MODE
X-
DCM
ACM
AUX
X POSITION MEASUREMENT
as follows:
TOUCH
TOUCH
R
TOUCH
PSU PMC CMC TDM LPM AVG FIFO APER
Yes
Yes
No
, providing information about the pres-
1
). Depending on the known physical
______________________________________________________________________________________
X+
V
DD
Yes
Yes
Yes
Y+
Y-
1
3
Pressure Measurements
ADC
INPUT
Yes
Yes
No
PANEL
1
X-
Y POSITION MEASUREMENT
Yes
Yes
No
Controllers with I
TOUCH
R
Yes
TOUCH
No
—
INPUT
resistance.
ADC
Yes
Yes
Yes
X+
3
Y+
Y-
Yes
No
No
V
DD
Yes
No
No
If only a Z1 measurement is available, compute
R
The power applied across the panel during pressure
measurements is greatly dependent on R
the physical position of the touch. The maximum power
dissipation in the panel during a pressure measurement
is approximately P
power dissipation condition is observed when the point
of contact is in the top left corner of the panel sensor.
Figure 5. Pressure Measurements
R
TOUCH
TOUCH
PANEL
PUR
PUF
Yes
Yes
No
X-
Z1 PRESSURE MEASUREMENT
R
TOUCH
=
⎛
⎝ ⎜
as follows:
CONT MTAG ETAG
R
Yes
No
No
XPLATE POSITION
R
TOUCH
=
2
N BITX
INPUT
2
X
R
ADC
Yes
Yes
No
XPLATE
X+
C/SPI Interface
Z
2
= V
Y+
Y-
⎞
⎠ ⎟
Yes
Yes
No
⎛
⎝ ⎜
V
DD
⎛
⎜
⎝
DD
2
N BI
X
2
Z
2
POSITION
1
PANEL
2
T T Z
/R
N BITX
X-
Z2 PRESSURE MEASUREMENT
Z1, Z2
X, Y,
−
TOUCH
Yes
Yes
No
1
⎞
⎠ ⎟
−
R
YPLATE
⎞
⎟
⎠
EINT CINT
R
Yes
. This maximum
No
No
TOUCH
⎛
⎜
⎝
Z
Z
2
⎛
⎝ ⎜
1
1
TOUCH
−
Yes
X+
−
No
No
Y
1
POSITION
2
⎞
⎟
⎠
N BIT
Y+
Y-
COR
ADC
INPUT
INT
Yes
Y Y
No
No
and
V
DD
19
⎞
⎠ ⎟