ucb1200 NXP Semiconductors, ucb1200 Datasheet - Page 16

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

Philips Semiconductors
TOUCH SCREEN INTERFACE
The UCB1200 contains a universal resistive touch screen interface for 4-wire resistive touch screen, capable of
performing position, pressure and plate resistance measurements. In addition the touch screen can be programmed to
generate interrupts when the touch screen is pressed. The last mode is also active when the UCB1200 is set in the
stand-by mode.
The touch screen interface connects to the touch screen by four wires: TSPX, TSMX, TSPY and TSMY. Each of these
pins can be programmed to be floating, powered or grounded in the touch screen switch matrix. The setting of each touch
screen pin is programmable through the touch screen control register. Possible conflicting settings (grounding and
powering of a touch screen pin at the same time) are detected by the UCB1200. In that case the touch screen pin will be
grounded.
The UCB1200’s internal voltage reference (V
the touch screen biasing independent of supply voltage and temperature variations. Four low pass filters, one on each
touch screen terminal, are built in to minimize the noise coupled from the LCD into the touch screen signals. An LCD
typically generates large noise glitches on the touch screen, since they are closely coupled. The influence of the glitches
can nevertheless be minimized by performing measurements when the LCD is quiet. This can be done by synchronizing
the measurement and the video driver with the ADCSYNC pin.
1998 Jul 22
Advanced modem/audio analog front-end
adc_input[2:0]
ts..ground
ts..power
vssa3
Fig.11 Block diagram of the touch screen interface.
ref
) is used as reference voltage for the touch screen bias circuit. This makes
analog mux
16
vssa1
touch screen
bias voltage
touch screen
current monitor
tsc_mode
tsc_mode_sel
to adc input
tsc_bias_ena
Product specification
vdda1
UCB1200