at42qt1070 ATMEL Corporation, at42qt1070 Datasheet - Page 9

• Manufacturer Part Number: at42qt1070
• Description: Qtouch 7-channel Sensor Ic
• Manufacturer: ATMEL Corporation

2. Overview
2.1
2.2
2.2.1
2.2.2
2.3
2.4
9596A–AT42–10/10
Introduction
Modes
Keys
Input/Output (IO) Lines
Comms Mode
Standalone Mode
The AT42QT1070 (QT1070) is a digital burst mode charge-transfer (QT
driver. The device can sense from one to seven keys, dependent on mode.
The QT1070 includes all signal processing functions necessary to provide stable sensing under
a wide variety of changing conditions, and the outputs are fully debounced. Only a few external
parts are required for operation and no external Cs capacitors are required.
The QT1070 modulates its bursts in a spread-spectrum fashion in order to heavily suppress the
effects of external noise, and to suppress RF emissions. The QT1070 use a dual-pulse method
of acquisition. This provides greater noise immunity and eliminates the need for external
sampling capacitors, allowing touch sensing using a single pin.
The QT1070 can operate in comms mode where a host can communicate with the device via an
I
Suppression
On for keys.
The QT1070 can operate in a standalone mode where an I
required. To enter standalone mode, connect the Mode pin to Vdd before powering up the
QT1070.
In standalone mode, the start-up values are hard coded in firmware and cannot be changed.
The default start-up values are used. This means that key detection is reported via their
respective IOs. The Guard channel feature is automatically implemented on key 0 in standalone
mode. This means that this channel gets priority over all other keys going into touch.
Dependent on mode, the QT1070 can have a minimum of one key and a maximum of seven
keys. These can be constructed in different shapes and sizes. See
recommended dimensions.
Unused keys should be disabled by setting the averaging factor to zero (see
page
The status register can be read to determine the touch status of the corresponding key. It is
recommended using the open-drain CHANGE line to detect when a change of status has
occurred.
There are no IO lines in comms mode.
In Standalone mode pins OUT0 – OUT4 can be used as open drain outputs for driving LEDs.
2
C-compatible bus. This allows the user to configure settings for Threshold, Adjacent Key
• Comms mode – 1 to 7 keys (or 1 to 6 keys plus Guard Channel)
• Standalone mode – 1 to 4 keys plus a Guard Channel
21).
®
(AKS
®
), Detect Integrator, Low Power (LP) Mode, Guard Channel and Max Time
2
C-compatible interface is not
“Features” on page 1
AT42QT1070
™
) capacitive sensor
Section 5.9 on
for the
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