AT42QT1111-MU Atmel, AT42QT1111-MU Datasheet - Page 20

• Manufacturer Part Number: AT42QT1111-MU
• Description: IC TOUCH SENSOR 11KEY QFN
• Manufacturer: Atmel
• Series: QTouch™r
• Type: Capacitiver

Specifications of AT42QT1111-MU

• Touch Panel Interface: 10, 2-Wire
• Number Of Inputs/keys: 11 Key
• Data Interface: Serial, SPI™
• Voltage Reference: Internal
• Voltage - Supply: 3 V ~ 5.5 V
• Current - Supply: 12mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN Exposed Pad
• Output Type: Logic
• Interface: SPI
• Input Type: Logic
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AT42QT1111-MU; AT42QT1111-MUTR

4.10
4.10.1
4.10.2
4.11
4.11.1
20
Self-test Functions
Signal Processing
AT42QT1111-MU/AT42QT1111-AU
Internal Hardware Tests
Functional Checks
Detection Integrator
Figure 4-9.
Internal hardware tests check for hardware failure in the device’s internal memory areas and
data paths. Any failure detected in the function or contents of application ROM, RAM or registers
causes the device to reset itself.
The application code is scanned with a CRC check routine to confirm that the application data is
all correct.
The RAM and registers are checked periodically (every 10 seconds) for dynamic and static
failures.
Functional checks confirm that the device is operating within expected parameters; any failure
detected in these tests is notified to the system host. The device will continue to operate in the
event that such functional failures are detected.
The functional tests are:
These tests are carried out as the particular functions are used. For example, the EEPROM is
checked when the device attempts to load data from EEPROM, and the channel signals are
checked when a measurement is carried out.
Note:
The device features a detection integration mechanism, which acts to confirm a detection in a
robust fashion. A per-key counter is incremented each time the key has exceeded its threshold.
When this counter reaches a preset limit the key is finally declared to be touched. For example,
if the DI limit is set to 10, then a key’s signal must fall by more than the key threshold, and
remain below that level for 10 acquisitions, before the key is declared to be touched.
Similarly, the DI is applied to a key that is going out of detect: it must take 10 acquisitions where
the signal has not exceeded its detect threshold before it is declared to leave touch.
• Check that the channel-measurement signals are within the defined range.
• Confirm that data stored in the EEPROM is valid.
If a particular channel is unused, the threshold of that channel should be set to 0 to
prevent the incorrect reporting of the unused channel as being in an error state.
Guard Channel Example
Guard Channel
Formed of One Key
Key Pad Formed
of Six Keys
9571A–AT42–02/10