ucb1200 NXP Semiconductors, ucb1200 Datasheet - Page 17

• Manufacturer Part Number: ucb1200
• Description: Advanced Modem/audio Analog Front-end
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Product specification
Advanced modem/audio analog front-end
UCB1200
Vdda
schmitt trigger
Rint
tspx
tsmy
tspy
tsmx
schmitt trigger
Fig.12 Touch screen setup for interrupt detection.
In addition to the measurements mentioned above, the touch screen can also act as an interrupt source. In this mode
the X plate of the touch screen has to be powered and the Y plate has to be grounded. In this case the touch screen is
not biased by the active touch screen bias circuit, but by a resistor to V
. This configuration simply biases the touch
DDA1
screen and the UCB1200 does not consume power unless the touch screen is touched. The voltage on the X plate
terminals drops if the screen is pressed. This voltage drop is detected by Schmitt-trigger circuits, of which the outputs
are connected to the interrupt control block. A touch screen interrupt is generated either when the touch screen is
pressed (falling edge enabled) or when the touch screen is released (rising edge enabled). It can be used to activate the
system around the UCB1200 to start a touch screen read-out sequence. The internal Schmitt-trigger circuits are
connected to the TSPX and TSMX signals after the built in low pass filters. This reduces the number of spurious
interrupts, due to the coupling between the LCD screen and the touch screen sensors.
Each of the four touch screen signals can be selected as input for the built in 10 bit ADC, which is used to determine the
voltage on the selected touch screen pin. The flexible switch matrix and the multi- functional touch screen bias circuit
enables the user of the UCB1200 to set each desired touch screen configuration.
The setting of the touch screen bias circuit and the ADC input multiplexer is determined by the setting of TSC_MOD[n]
in the touch screen control register according the following table.
1998 Jul 22
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