mk712 Integrated Device Technology, mk712 Datasheet - Page 8

• Manufacturer Part Number: mk712
• Description: Touch Screen Controller
• Manufacturer: Integrated Device Technology

Recommended Method for Reading Points
Warning–When Using a Switching Regulator Power Supply
IDT™ / ICS™ TOUCH SCREEN CONTROLLER
MK712
TOUCH SCREEN CONTROLLER
If the user is pressing lightly on the touch screen, it is likely that the screen contact will be intermittent. The screen
will bounce, causing false points. This effect can be reduced by insuring that the screen is touched both before and
after a conversion. By doing this, the first and last point in a series of points are discarded. The following algorithm
checks that a point has valid touches both before and after a conversion, and it distinguishes between
change-in-touch interrupts and conversion complete interrupts. Register 6 bits 0, 1, and 2 must all be true (logical
1) in order to use this method.
When using the MK712 in a system where the power is supplied by a switching regulator, do not perform screen
conversions when the regulator is operating in the power saving mode. Some switching regulators feature a low
power mode (for example, Linear Technology’s “Burst Mode”) where the output is turned on and off in order to save
power. The extra power supply noise generated when using this mode causes spurious data points to be returned
from the MK712, so it should be disabled when the MK712 is doing screen conversions.
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TOUCH SCREEN CONTROL
MK712
REV L 070805