MXB7846 Ver la hoja de datos (PDF) - Maxim Integrated
Número de pieza
componentes Descripción
Fabricante
MXB7846 Datasheet PDF : 24 Pages
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2.375V to 5.25V, 4-Wire Touch-Screen Controller
with Internal Reference and Temperature Sensor
SCREEN TOUCHED HERE
PENIRQ
CS
DCLK
1
2
3
4
5
6
7
8
1
2
3
12 13 14 15 16
DIN
S A2 A1 A0 M S/D PD1 PD0
INTERRUPT PROCESSOR
tTOUCH
NO RESPONSE TO TOUCH⎯MASK PENIRQ
PENIRQ ENABLED
Figure 6. PENIRQ Timing Diagram
MEASURE X- POSITION
X+
Y+
+
V
-
MEASURE Z1
RTOUCH
X- POSITION
X-
Y-
OPEN CIRCUIT
X+
Y+
RTOUCH
+
V
-
X-
Y-
OPEN CIRCUIT
OPEN CIRCUIT
X+
Y+
RTOUCH
+
V
-
X-
Y- SENSE LINE
MEASURE Z2
Figure 7. Pressure Measurement Block Diagram
The first method performs pressure measurements
using a known X-plate resistance. After completing
three conversions (X-position, Z1, and Z2), use the fol-
lowing equation to calculate RTOUCH:
( ) RTOUCH = RXPLATE
×
⎛
⎝⎜
XPOSITION
4096
⎞
⎠⎟
×
⎡⎛
⎣⎢⎢⎝⎜
Z2
Z1
⎞
⎠⎟
⎤
− 1⎥
⎦⎥
The second method requires knowing both the X-plate
and Y-plate resistance. Three conversions are required in
this method: the X-position, Y-position, and Z1-position.
Use the following equation to calculate RTOUCH:
RTOUCH
=
⎧⎪⎛
⎨⎩⎪⎝⎜
RXPLATE
Z1
⎞
⎠⎟
×
⎛
⎝⎜
XPOSITION
4096
⎞
⎠⎟
×
⎡⎛
⎣⎢⎢⎝⎜
4096 ⎞
Z1 ⎠⎟
−1
⎧
− ⎨RYPLATE
⎩
×
⎛
⎝⎜
YPOSITION
4096
⎞
⎠⎟
⎫
⎬
⎭
Internal Temperature Sensor
The MXB7846 provides two temperature measurement
options: single-ended conversion and differential con-
version. Both temperature measurement techniques rely
on the semiconductor junction’s temperature character-
istics. The forward diode voltage (VBE) vs. temperature
is a well-defined characteristic. The ambient tempera-
ture can be calculated by knowing the value of VBE at a
fixed temperature and then monitoring the change in
that voltage as the temperature changes. The single
conversion method requires calibration at a known tem-
perature, but only needs a single reading to calculate
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