ucb1400 NXP Semiconductors, ucb1400 Datasheet - Page 27

• Manufacturer Part Number: ucb1400
• Description: Audio Codec With Touch Screen Controller And Power Management Monitor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 09611
Product data
Fig 19. Touch screen setup for pressure-1 measurement (see
TSMY
VBIAS
TSMX
TOUCH
10.2.2 Pressure measurement
R
X1
R
Y1
R
1 k
R
The pressure applied to the touch screen can be determined. In fact, the contact
resistance between the X and Y plates is measured, which is a good indication of the
size of the pressed spot and the applied pressure. A soft stylus, e.g., a finger, leads to
a rather large contact area between the two plates when a large pressure is applied.
A hard stylus, e.g., a pen, leads to less variation in measured contact resistance
since the contact area is rather small.
One plate is biased at one or both terminals during this pressure measurement,
whereas the other plate is grounded, again on one or both terminals. The current
flowing through the touch screen is a direct indication for the resistance between both
plates. A compensation for the series resistance, formed by the touch screen plates
and the internal 1 k resistance of the UCB1400 will improve the accuracy of this
measurement.
t
X2
VBIAS
R
Y2
TSPX
TSPY
TO ADC
Rev. 02 — 21 June 2002
TSMY
VBIAS
Table
TSMX
9).
Audio codec with touch screen controller
1 k
TSPX
and power management monitor
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
VBIAS
TSPY
UCB1400
TO ADC
SN00248
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