OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

AT42QT1070-SSUR

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P34
7
AT42QT1070 [DATASHEET]
9596C–AT42–05/2013
Figure 1-3. Typical Circuit – Comms (20-pin VQFN)
Figure 1-4. Typical Circuit – Standalone (20-pin VQFN)
For component values in Figure 1-1, 1-2, 1-3, and 1-4, check the following sections:
Section 3.1 on page 12: Series resistors (Rs0 – Rs6 for comms mode and Rs0 – Rs4 for standalone mode)
Section 3.2 on page 12: LED traces
Section 3.4 on page 12: Power Supply (voltage levels)
Section 4.4 on page 14: SDA, SCL pull-up resistors
Rs6
C1
K4
Rs5
Rs4
Rs3
Rs2
Rs1
K3
K2
K1
9
QT1070
SCL
15
SDA
12
RESET
13
CHANGE
14
KEY6
16
KEY5
17
KEY4
1
KEY3
2
KEY2
3
KEY1
4
KEY0
5
8
Vss
Rs0
K0
Vss
Vdd
K5
K6
R
SCL
Vdd
Vdd
Vss
11
MODE (Vss)
N/C
N/C
18
N/C
19
N/C
20
N/C
7
N/C
6
10
CHANGE
SDA
RESET
R
SDA
Vdd
R
CHG
R
RST
Rs
OUT2
K4
Rs
OUT3
RL
OUT1
Rs4
Rs3
Rs2
Rs1
K3
K2
K1
OUT0
12
RESET
13
OUT4
14
OUT3
15
OUT2
16
OUT1
17
KEY4
1
KEY3
2
KEY2
3
KEY1
KEY0
5
Vss
Rs0
K0
R
OUT4
RESET
C
OUT1
C
OUT2
C
OUT3
Vss
C
OUT4
C
OUT0
8
QT1070
Vss
OUTPUTS
OUTPUTS
N/C
N/C
18
N/C
19
N/C
20
N/C
7
N/C
6
10
4
R
OUT0
Vss
C1
9
Vss
Vdd
Vdd
MODE (Vdd)
11
COUT1, 2 3and are optional
COUT0 4and are optional
R1
Vdd
8
AT42QT1070 [DATASHEET]
9596C–AT42–05/2013
2. Overview
2.1 Introduction
The AT42QT1070 (QT1070) is a digital burst mode charge-transfer (QT
™
) capacitive sensor 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 uses 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.
2.2 Modes
2.2.1 Comms Mode
The QT1070 can operate in comms mode where a host can communicate with the device via an I
2
C bus. This allows
the user to configure settings for Threshold, Adjacent Key Suppression (AKS), Detect Integrator, Low Power (LP)
Mode, Guard Channel and Max Time On for keys.
2.2.2 Standalone Mode
The QT1070 can operate in a standalone mode where an I
2
C interface is not 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.
2.3 Keys
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 “Features” on page 1 for the recommended dimensions.
Comms mode – 1 to 7 keys (or 1 to 6 keys plus Guard Channel)
Standalone mode – 1 to 4 keys plus a Guard Channel
Unused keys should be disabled by setting the averaging factor to zero (see Section 5.9 on page 18).
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.
2.4 Input/Output (IO) Lines
There are no IO lines in comms mode.
In Standalone mode pins OUT0 – OUT4 can be used as open drain outputs for driving LEDs.
2.5 Acquisition/Low Power Mode (LP)
There are 255 different acquisition times possible. These are controlled via the LP mode byte (see Section 5.11 on
page 19) which can be written to via I
2
C communication.
LP mode controls the intervals between acquisition measurements. Longer intervals consume lower power but have
an increased response time. During calibration, touch and during the detect integrator (DI) period, the LP mode is
temporarily set to LP mode 1 for a faster response.
9
AT42QT1070 [DATASHEET]
9596C–AT42–05/2013
The QT1070 operation is based on a fixed cycle time of approximately 8 ms. The LP mode setting indicates how
many of these periods exist per measurement cycle. For example, If LP mode = 1, there is an acquisition every cycle
(8 ms). If LP mode = 3, there is an acquisition every 3 cycles (24 ms). If a high Averaging Factor (see Section 5.9 on
page 18) setting is selected then the acquisition time may exceed 8 ms.
LP settings above mode 32 (256 ms) result in slower thermal drift compensation and should be avoided in
applications where fast thermal transients occur.
2.6 Adjacent Key Suppression (AKS) Technology
The device includes the Atmel-patented Adjacent Key Suppression (AKS) technology, to allow the use of tightly
spaced keys on a keypad with no loss of selectability by the user.
There can be up to three AKS groups, implemented so that only one key in the group may be reported as being
touched at any one time. Once a key in a particular AKS group is in detect no other key in that group can go into
detect. Only when the key in detect goes out of detection can another key go into detect state.
The keys which are members of the AKS groups can be set (see Section 5.9 on page 18). Keys outside the group
may be in detect simultaneously.
2.7 CHANGE Line (Comms Mode Only)
The CHANGE line is active low and signals when there is a change of state in the Detection or Input key status
bytes. It is cleared (allowed to float high) when the host reads the status bytes.
If the status bytes change back to their original state before the host has read the status bytes (for example, a touch
followed by a release), the CHANGE
line will be held low. In this case, a read to any memory location will clear the
CHANGE
line.
The CHANGE
line is open-drain and should be connected via a 47 k resistor to Vdd. It is necessary for minimum
power operation as it ensures that the QT1070 can sleep for as long as possible. Communications wake up the
QT1070 from sleep causing a higher power consumption if the part is randomly polled.
Note: The CHANGE
line is pulled low 100 ms after power-up or reset.
2.8 Types of Reset
2.8.1 External Reset
An external reset logic line can be used if desired, fed into the RESET pin. However, under most conditions it is
acceptable to tie RESET
to Vdd.
2.8.2 Soft Reset
The host can cause a device reset by writing a nonzero value to the RESET byte. This soft reset triggers the internal
watchdog timer on a 125 ms interval. After 125 ms the device resets and wakes again.
The device NACKs any attempts to communicate with it during the first 30 ms of its initialization period.
2.9 Calibration
Writing a non-zero value to the calibration byte can force a recalibration at any time. This can be useful to clear out a
stuck key condition after a prolonged period of uninterrupted detection.
Note: A calibrate command clears all key status bits and the overflow bit (until it is checked on the next cycle).
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P34

AT42QT1070-SSUR

Mfr. #:
Buy AT42QT1070-SSUR
Manufacturer:
Microchip Technology
Description:
Capacitive Touch Sensors QTouch 7 Channel Touch Sensor IC
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet