CONFIDENTIAL - RELEASED ONLY UNDER NONDISCLOSURE AGREEMENT (NDA)
Document Number: 001-81827 Rev. *E Page 5 of 24
TrueTouch Features Overview
Charger Armor
Charger Armor enables touchscreens in handsets, cameras,
GPS systems, and other mobile devices to function while
connected to noisy chargers. Low-cost, third-party, and
after-market battery chargers can generate large levels of
common-mode noise that directly couples into the touchscreen
sensor during a touch. This noise degrades touch performance,
causing inaccurate and phantom touches. Many mobile phone
vendors worked together to create the EN62684 and EN301489
standards, which set limits for the noise spectrum and magnitude
for battery chargers. Charger Armor enables the CY8CTMA44X
to go beyond these standards and operate with an even broader
range of chargers.
Water Rejection
Water droplets can cause false touches to be reported. However,
the CY8CTMA44X continues to operate in the presence of water
droplets or condensation. The CY8CTMA44X enables water
rejection through its ability to sense both self and mutual capaci-
tance.
Wet Finger Tracking
In a touchscreen system, moisture on fingers can cause false
touches to be reported and make tracking of fingers across the
screen difficult. The CY8CTMA44X can detect and track fingers
that are wet and enable more robust functionality of the touch-
screen. This includes sweaty fingers touching the screen or
fingers moving across the screen with mist covering it.
Grip Suppression
The CY8CTMA44X enables grip suppression for a natural user
experience. While using a touchscreen device, the user can grip
the device such that the gripping fingers touch the screen. This
may cause a loss in touchscreen performance due to detection
of unintended fingers. Grip suppression is the ability to filter out
unintended touches at the edge of the touchscreen while still
supporting normal touchscreen functionality in the rest of the
touchscreen. The CY8CTMA44X interprets the quality and size
of touches at the edge of a screen, tracks them as they move,
and ensures that they do not trigger false touches while keeping
the entire touchscreen surface responsive to touch and finger
tracking. The grip suppression areas are register configurable.
Large Finger Tracking
A well-designed touchscreen system must correctly report a
large finger or thumb as only a single touch. If this is not
supported, a large finger can incorrectly be reported as two or
more touches, hampering the user experience. When an object,
such as a thumb, is pressed against the touchscreen sensor, the
CY8CTMA44X ensures that only one touch is reported at the
center of the object.
Large Object Detection and Rejection
It is important to be able to detect the presence of a large object
on the touchscreen sensor. Two common examples are touching
a palm on the screen when typing and pressing a side of a face
on the screen when talking on a phone. A large object, such as
a fist, palm, or side of a face, can be determined by the
CY8CTMA44X from the touchscreen data. The presence of a
large object may either be rejected or reported to the host.
Look-for-Touch
Look-for-touch is a low-power and fast-wakeup mode, in which
the touchscreen sensor is measured for an increase in capaci-
tance. An increase in capacitance indicates that a touch is present.
Because it is only necessary to detect a finger’s presence, and not
location, the sensing can be done at a much lower SNR, requiring
less time and power. Look-for-touch sensing is used to implement
multiple functions, including wake-on-touch and fast first-touch
response.