TSC2117 datasheet(73/192 Pages) TI

73 / 192 page

GPIO1/GPIO2

Data_Available

PenInterrupt

AVDD

50kW

LowWhen TouchDetectionIsDisabled

TEMP1or TEMP2MeasurementIs Activated

HighWhen YP orXP DriversOn

DuringX-Y orX-Y-ZMeasurement

TEMP1or TEMP2MeasurementIs Activated

X+

B0214-02

GlitchRemoval

andDebounce

Logic

TEMP DIODE

TEMP2

TEMP1

TSC2117

Low-Power Audio Codec With Embedded miniDSP, Stereo Class-D

Speaker Amplifier, and Smart Four-Wire Touch-Screen Controller

www.ti.com

SLAS550A – APRIL 2009 – REVISED JUNE 2009

select which signal is used, page 3/register 3, bits D1–D0 must be programmed. A detailed block diagram

is shown in Figure 5-41. While in the power-down mode, the Y– driver is ON and connected to TSVSS,

and the X+ pin is connected through an on-chip pullup resistor to AVDD. In this mode, the X+ pin is also

connected to a digital buffer and multiplexer to drive the GPIO1 or GPIO2 output. When the panel is

touched, the X+ input is pulled to ground through the touch screen and the pen-interrupt signal goes LOW

due to the current path through the touch-screen panel to TSVSS, initiating an interrupt to the processor.

During the measurement cycles for X– and Y– position, the X+ input is disconnected from the

pen-interrupt circuit to prevent any leakage current from the pullup resistor flowing through the touch

screen, and thus causing conversion errors. The TSC2117 uses either the internal oscillator or MCLK for

the debounce logic.

Figure 5-41. GPIO1/GPIO2 Functional Block Diagram

In modes where the TSC2117 must detect if the screen is still touched (for example, when doing a

host-initiated X and Y conversion), the TSC2117 must reset the drivers so that the 50-k

Ω resistor is

connected. Because of the high value of this pullup resistor, any capacitance on the touch screen inputs

causes a long delay time and may prevent the detection from occurring correctly. To prevent this, the

TSC2117 has a circuit that allows any screen capacitance to be precharged, so that the pullup resistor is

not the only source for the charging current. The time allowed for this precharge, as well as the time

needed for sensing and for voltage stabilization if the screen is still touched, can be controlled by register

programming. Precharge time can be set by writing to page 3/register 4, bits D6–D4. Sense time can be

set by writing to page 3, register 4, bits D2–D0, and voltage stabilization time can be set by writing to

page 3/register 5, bits D2–D0.

The function of the GPIO1 or GPIO2 output is controlled by writing to page 3/register 3, bits D1–D0. The

pen-touch detection circuit can be disabled by writing to page 3/register 4, bit D7.

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TSC2117 Datasheet(PDF) 73 Page - Texas Instruments

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