PENIRQ Output

PENIRQ

V

DD

10kΩ

30k

to 100k

Ω

Ω

ON

Y+ or X+ drivers on,

or TEMP0, TEMP1

measurements activated

Y+

X+

Y–

TEMP0

TEMP1

TEMP

DIODE

HIGH except

when TEMP0,

TEMP1 activated

V

DD

V

DD

TSC2003-Q1

SBAS454 – DECEMBER 2008 ........................................................................................................................................................................................... www.ti.com

The pen-interrupt output function is shown in Figure 18. By connecting a pullup resistor to VDD (typically 100 kΩ),

the PENIRQ output is high. While in the 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 due to the current path through the panel to

GND, initiating an interrupt to the processor. During the measurement cycle for X, Y, and Z positions, the X+

input is disconnected from the PENIRQ pulldown transistor to eliminate any leakage current from the pullup

resistor to flow through the touch screen, thus causing no errors.

Figure 18. PENIRQ Functional Block Diagram

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

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

pulldown transistor and disable the pen-interrupt output function regardless of the value of the PD0 bit. Under

these conditions, the PENIRQ output is forced low. Furthermore, if the last command byte written to the

TSC2003 contains PD0 = 1, the pen-interrupt output function is disabled and is not able to detect when the panel

is touched. To re-enable the pen-interrupt output function under these circumstances, a command byte needs to

be written to the TSC2003 with PD0 = 0.

Once the bus master sends the address byte with R/W = 0 (see Figure 12) and the TSC2003 sends an

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

then the pen-interrupt function is enabled at the end of a conversion. This is approximately 10

µs (12-bit mode)

or 7

µs (8-bit mode) after the TSC2003 receives a Stop/Start condition following the reception of a command

byte (see Figure 14 and Figure 16 for further details of when the conversion cycle begins).

In both cases listed above, it is recommended that the master processor mask the interrupt which the PENIRQ is

associated with whenever the host writes to the TSC2003. This prevents false triggering of interrupts when the

PENIRQ line is disabled in the cases listed above.

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Product Folder Link(s): TSC2003-Q1