TSC2100 Datasheet, PDF (20/71 Pages) Texas Instruments – PROGRAMMABLE TOUCH SCREEN CONTROLLER WITH INTEGRATED STEREO AUDIO CODEC AND HEADPHONE/SPEAKER AMPLIFIER

TSC2100
SLAS378− NOVEMBER 2003
www.ti.com
Touch Detect/Data Available
The pen interrupt/data available (PINTDAV) output function is detailed in Figure 18. While in the power-down mode, the
Y– driver is ON and connected to AVSS 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 mux to drive the PINTDAV 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 panel to AVSS, 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.
PINTDAV
DATAV
50 kΩ
Temp1
Temp2
Y+
High Except When
Temp1, Temp2 Activated
X+
Temp
Diode
Y−
ON
Y+ or X+ Drivers On or
Temp1, Temp2
Measurements Activated
Figure 18. PINTDAV Functional Block Diagram
In modes where the TSC2100 needs to detect if the screen is still touched (for example, when doing a PINTDAV initiated
X, Y, and Z conversion), the TSC2100 must reset the drivers so that the 50-kΩ 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 TSC2100 has a circuit that allows any screen capacitance to be
precharged, so that the pullup resistor does not have to be the only source for the charging current. The time allowed for
this precharge, as well as the time needed to sense if the screen is still touched, can be set in the configuration control
register D5−D0 of REG05H/Page1.
This does point out, however, the need to use the minimum capacitor values possible on the touch screen inputs. These
capacitors may be needed to reduce noise, but too large a value increases the needed precharge and sense times, as well
as panel voltage stabilization time.
The function of PINTDAV output is programmable and controlled by writing to the bits D15−D14 of REG 01H/Page1 as
described in the Table 2.
Table 2. Programmable PINTDAV Functionality
D15−D14
PINTDAV FUNCTION
00
Acts as PEN interrupt (active low) only. When PEN touch is detected, PINTDAV goes low.
01
Acts as data available (active low) only. The PINTDAV goes low as soon as one set of ADC conversions are completed for data
of X,Y, XYZ, battery input, or auxiliary input selected by D13−D10 in REG00H/Page1. The resulting A/D output is stored in the
appropriate registers. The PINTDAV remains low and goes high only after this complete set of registers selected by D13−D10
REG00H/Page1 is read out.
10
Acts as both PEN interrupt and data available. When PEN touch is detected, PINTDAV goes low and remains low. The PINTDAV
11
goes high only after one set of A/D conversions is completed for data of X,Y, XYZ, battery input, or auxiliary input selected by
D13−D10 in REG00H/Page1.
NOTE: See the section Conversion Time Calculation for the TSC2100 in this data sheet for the timing diagrams.
Pen-touch detect circuit is disabled during hardware power down.
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