
On
GPIO1/GPIO2
Data_Available
PenInterrupt
AVDD
50kW
LowWhen TouchDetectionIsDisabled
OR
TEMP1or TEMP2MeasurementIs Activated
HighWhen YP orXP DriversOn
DuringX-Y orX-Y-ZMeasurement
OR
TEMP1or TEMP2MeasurementIs Activated
YP
X+
YN
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
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.
APPLICATION INFORMATION
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