UCB1300 Просмотр технического описания (PDF) - Philips Electronics

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производитель

UCB1300

Advanced modem/audio analog front-end

Philips Electronics 

Philips Semiconductors

Advanced modem/audio analog front-end

Preliminary specification

UCB1300

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.

Vdda

Rint

schmitt trigger

tsmy

tspx

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 VDDA1. This configuration simply biases the touch

screen and the UCB1300 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 UCB1300 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 UCB1300 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.

1999 Jul 20

18

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