AK4184 Datasheet, PDF (19/36 Pages) Asahi Kasei Microsystems – TSC with Keypad Scanner and GPIO Expander

[AK4184]
■ Pen Interrupt
The AK4184 has a pen interrupt function to detect a pen touch. The pen interrupt function is enabled during power-
down state. The YN pin is connected to GND during the pen interrupt enabled state. The XP pin is pulled up via an
internal resistor (Ri), typically 50kΩ. If the touch plate is pressed by pen, the current flows via <AVDD> – <Ri> –
<XP> –<the plates> - <YN>- <GND>. The resistance of the plate is generally several hundreds, and PENIRQN is
forced to a “L” level. If the pen is released, PENIRQN returns to a “H” level because two plates are disconnected,
and the current doesn’t flow between the two plates. PENIRQN pin is a buffer type. The “H” level is specified by
IOVDD.
The operation of PENIRQN is related to PD bit. The pen interrupt function is disabled and stays “H” irrespective of
the pen touch when the PD bit is “1”. When the PD bit is “0”, the PENIRQN pin is forced “H” from the falling edge
of the sixth SCLK to the rising edge of CSN. The pen interrupt function is valid when the CSN pin is “H”. The
PENIRQN pin stays low when the touch panel is pressed, and stays high when the touch panel is not pressed.
The pen interrupt function is determined by the present PD bit setting when the host writes to or reads from the
register other than the pen touch block.
The touch panel block is able to power down when the TPPD bit is “1” (Table 25). All the touch panel drivers turn off
in this state and the pen interrupt function is not valid. The current through the touch screen does not flow even
through the panel is pressed.
IOVDD
Ri =
50kΩ
AVDD
EN
Driver OFF
PENIRQN
AVDD
XP
YN
Driver ON
Figure 9. PENIRQ Functional Block Diagram
MS0603-E-00
19
2007/04