ucb1400 NXP Semiconductors, ucb1400 Datasheet - Page 28

• 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 20. Touch screen setup for X plate resistance measurement.
Fig 21. Touch screen setup for interrupt detection.
TO ADC
1 k
TSMY
10.2.3 Plate resistance measurement
10.2.4 Interrupt mode
TSMX
TSMY
TOUCH
R
TSMX
X1
R
Y1
The plate resistance of a touch screen varies a lot due to processing spreads.
Knowing the actual plate resistance makes it possible to compensate for the plate
resistance effects in the pressure resistance measurements. Secondly, the plate
resistance decreases when two or more spots on the touch screen are pressed. In
that case, a part of one plate, e.g., the X plate, is shorted by the other plate, which
decreases the actual plate resistance.
The plate resistance measurement is executed in the same way as the pressure
resistance measurement. In this case, only one of the two plates is biased, and the
other plate is kept floating. The current through the connected plate is again a direct
indication of the connected resistance.
R
X1
R
Y1
R
R
t
X2
R
Y2
AV
R
R
TSPX
t
X2
DD
R
VBIAS
R
TSPY
int
Y2
Rev. 02 — 21 June 2002
TSPX
TSPY
TSMY
TSMY
AV
DD
R
int
SCHMITT TRIGGER
Audio codec with touch screen controller
1 k
TSMX
TSMX
TO ADC
and power management monitor
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
TSPX
TSPX
SCHMITT TRIGGER
VBIAS
UCB1400
TSPY
TSPY
SN00249
SN00250
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