TSC2007IPW datasheet(19/41 Pages) TI

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Touch Detect

GND

PenTouch

X+

Y+

Y-

HighwhentheX+orY+

driverison,orwhenany

sensorconnection/short-

circuittestsareactivated.

GND

Sense

Viasgotosystemanaloggroundplane.

GND

Highwhen

theX+orY+

driverison.

Control

Logic

IRQ

VDD/REF

PENIRQ

Connectto

AnalogSupply

TSC2007

SBAS405 – MARCH 2007

OVERVIEW (continued)

The PENIRQ can be used as an interrupt to the host. RIRQ is an internal pull up with a programmable value of

either 50k

Ω (default) or 90kΩ. Write command '1011' (setup command) followed by data '0001' sets the pullup to

90k

Ω. NOTE: The first three bits must be '0's and the select bit is the last bit. To change the pullup back to

50k

Ω, issue write command '1011' followed by data '0000'.

An example for the Y-position measurement is detailed in Figure 27. The PENIRQ output is pulled high by an

internal pullup. While in power-down mode with PD0 = 0, the Y– driver is on and connected to GND, and the

PENIRQ output is connected to the X+ input. When the panel is touched, the X+ input is pulled to ground

through the touch screen, and PENIRQ output goes low because of the current path through the panel to GND,

initiating an interrupt to the processor. During the measurement cycle for X-, Y-, and Z-Position, the X+ input is

disconnected from the PENIRQ pull-down transistor to eliminate any pull-up resistor leakage current from

flowing through the touch screen, thus causing no errors.

In addition to the measurement cycles for X-, Y-, and Z-Position, commands that activate the X-drivers,

Y-drivers, and Y+ and X-drivers without performing a measurement, also disconnect the X+ input from the

PENIRQ pull-down transistor and disable the pen-interrupt output function, regardless of the value of the PD0

bit. Under these conditions, the PENIRQ output will be forced low. Furthermore, if the last command byte written

to the TSC2007 contains PD0 = 1, the pen-interrupt output function will be disabled and will not be able to detect

when the panel is touched. In order to re-enable the pen-interrupt output function under these circumstances, a

command byte must be written to the TSC2007 with PD0 = 0.

When the bus master sends the address byte with R/W bit = 0, and the TSC2007 sends an acknowledge, the

pen-interrupt function is disabled. If the command that follows the address byte contains PD0 = 0, then the

pen-interrupt function will be enabled at the end of a conversion. This is approximately 100

µs (12-bit mode) or

µs (8-bit mode) after the TSC2007 receives a STOP/START condition, following the receipt of a command

byte (see Figure 31 and Figure 30 for further details about when the conversion cycle begins).

In both cases previously listed, it is recommended that whenever the host writes to the TSC2007, the master

processor masks the interrupt associated to PENIRQ. This masking prevents false triggering of interrupts when

the PENIRQ line is disabled in the cases previously listed.

Figure 27. Example of a Pen-Touch Induced Interrupt via the PINTDAV Pin

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