QT60168C-ASG Atmel, QT60168C-ASG Datasheet - Page 17

IC TOUCH SENSOR 16KEY 32TQFP

QT60168C-ASG

Manufacturer Part Number
QT60168C-ASG
Description
IC TOUCH SENSOR 16KEY 32TQFP
Manufacturer
Atmel
Series
QMatrix™, QProx™r
Type
Capacitiver
Datasheets

Specifications of QT60168C-ASG

Number Of Inputs/keys
16 Key
Resolution (bits)
9, 11 b
Data Interface
Serial, SPI™
Voltage - Supply
3 V ~ 5 V
Current - Supply
25mA
Operating Temperature
-40°C ~ 105°C
Mounting Type
Surface Mount
Package / Case
32-TQFP, 32-VQFP
Output Type
*
Interface
*
Input Type
*
For Use With
427-1087 - BOARD EVAL QT60248-AS QMATRIX
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
QT60168C-ASG
Manufacturer:
Atmel
Quantity:
5 323
2.4
Touch Sensors Design Guide
Nearby LEDs
The most common form of electrode is a filled circle or rectangle of copper on a PCB, corresponding
loosely in shape to the key graphic. The PCB is then usually glued with an industrial adhesive such as a
two-sided acrylic sheet to the inside of the operator panel.
If LEDs are close (that is, less than 4 mm away) to capacitive sensors, you must give some
consideration to their change in capacitance between on and off states (and the possible change of the
LED driver's output impedance too). It is also necessary to consider the changes in the nature of their
drive circuitry.
If changes in capacitance of the LED and associated drive circuit couple to a touch sensor electrode, it is
possible to cause detection instability or touch keys that stick either on or off when the LED changes
state.
As a general rule, LEDs that are judged as close must be bypassed with a capacitor that has a typical
value of 1 nF
particularly important for LEDs that are pulled down or up to switch on, but are allowed to float when off.
Note that the bypass capacitor does not need to be physically close to the LED itself. Even if the
capacitor is several centimeters away from the LED, it will still serve its purpose. This may aid layouts
that are tight for space around the sensors.
Figure 2-3.
1. One example of acrylic bonding sheet includes 3M type 467MP, although there are other suppliers
2. Non critical value. The idea is to simply provide a constant low impedance path as seen by the sensor, on both
and types which may prove more suitable.
ends of the LED. Low means less than 1 k at 100 kHz
LOW or HIGH,
never Hi-Z
LOW or HIGH,
never Hi-Z
(2)
LED Circuits
if either end of the LED changes to a non-low impedance state at any point. This is
Vdd
HIGH or Hi-Z
LOW or Hi-Z
(1)
Vdd
...or...
General Advice
Vdd
10620D–AT42–04/09
2-7

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