QT112-S Atmel, QT112-S Datasheet - Page 6

• Manufacturer Part Number: QT112-S
• Description: SENSOR IC TOUCH/PROXMTY 1CH8SOIC
• Manufacturer: Atmel
• Series: QProx™r
• Type: Capacitiver

Specifications of QT112-S

• Rohs Status: RoHS non-compliant
• Touch Panel Interface: 1, 2-Wire
• Number Of Inputs/keys: 1 Key
• Resolution (bits): 14 b
• Data Interface: Serial
• Voltage Reference: Internal
• Voltage - Supply: 2.45 V ~ 5.25 V
• Current - Supply: 60µA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Output Type: Logic
• Interface: 2-Wire
• Input Type: Logic
• Package / Case: -
• Other names: 427-1007

2.1.5 F
The QT110 has no recalibration pin; a forced recalibration is
accomplished only when the device is powered up. However,
supply drain is so low it is a simple matter to treat the entire
IC as a controllable load; simply driving the QT110's Vdd pin
directly from another logic gate or a microprocessor port
(Figure 2-2) will serve as both power and 'forced recal'. The
source resistance of most CMOS gates and microprocessors
is low enough to provide direct power without any problems.
Note that most 8051-based micros have only a weak pullup
drive capability and will require true CMOS buffering. Any
74HC or 74AC series gate can directly power the QT110, as
can most other microprocessors.
Option strap configurations are read by the QT110 only on
powerup. Configurations can only be changed by powering
the QT110 down and back up again; again, a microcontroller
can directly alter most of the configurations and cycle power
to put them in effect.
2.2 OUTPUT FEATURES
The QT110 / QT110H are designed for maximum flexibility
and can accommodate most popular sensing requirements.
These are selectable using strap options on pins OPT1 and
OPT2. All options are shown in Table 2-1.
2.2.1 DC M
The output of the device can respond in a DC mode, where
the output is active-low (QT110) or active-high (QT110H)
upon detection. The output will remain active for the duration
of the detection, or until the Max On-Duration expires,
whichever occurs first. If the latter occurs first, the sensor
performs a full recalibration and the output becomes inactive
until the next detection.
In this mode, two Max On-Duration timeouts are available:
10 and 60 seconds.
2.2.2 T
This makes the sensor respond in an on/off mode like a flip
flop. It is most useful for controlling power loads, for
example in kitchen appliances, power tools, light switches,
etc.
Getting HB pulses with a pull-down resistor (QT110 shown; use
H eartBeat™ P ulses
ORCED
OGGLE
ODE
pull-up resistor with QT110H)
R o
S
M
O
ENSOR
ODE
UTPUT
2
3
4
Figure 2-3
O
O UT
O PT 1
O PT 2
R
UTPUT
+2 .5 to 5
ECALIBRATION
1
8
V dd
V ss
S NS 2
GAIN
S NS 1
7
5
6
M icro pro ce sso r
- 6 -
Max On-Duration in Toggle mode is fixed at 10 seconds.
When a timeout occurs, the sensor recalibrates but leaves
the output state unchanged.
2.2.3 P
This generates a pulse of 75ms duration (QT110 -
negative-going; QT110H - positive-going) with every new
detection. It is most useful for 2-wire operation, but can also
be used when bussing together several devices onto a
common output line with the help of steering diodes or logic
gates, in order to control a common load from several
places.
Max On-Duration is fixed at 10 seconds if in Pulse output
mode.
2.2.4 H
The output has a full-time HeartBeat™ ‘health’ indicator
superimposed on it. This operates by taking 'Out' into a
3-state mode for 350µs once before every QT burst. This
output state can be used to determine that the sensor is
operating properly, or, it can be ignored using one of several
simple methods.
QT110: The HeartBeat indicator can be sampled by using a
pulldown resistor on Out, and feeding the resulting
negative-going pulse into a counter, flip flop, one-shot, or
other circuit. Since Out is normally high, a pulldown resistor
will create negative HeartBeat pulses (Figure 2-3) when the
sensor is not detecting an object; when detecting an object,
the output will remain active for the duration of the detection,
and no HeartBeat pulse will be evident.
QT110H: Same as QT110 but inverted logic (use a
pull-down resistor instead of a pull-up etc.)
If the sensor is wired to a microprocessor as shown in Figure
2-4, the microprocessor can reconfigure the load resistor to
either ground or Vcc depending on the output state of the
device, so that the pulses are evident in either state.
Electromechanical devices will usually ignore this short
pulse. The pulse also has too low a duty cycle to visibly
activate LED’s. It can be filtered completely if desired, by
adding an RC timeconstant to filter the output, or if
interfacing directly and only to a high-impedance CMOS
input, by doing nothing or at most adding a small non-critical
capacitor from Out to ground (Figure 2-5).
Using a micro to obtain HB pulses in either output state
P O RT _M .x
P O RT _M .y
ULSE
EART
B
M
EAT
ODE
(QT110 or QT110H)
™ O
R
O
Figure 2-4
o
UTPUT
UTPUT
2
3
4
O U T
O P T 1
O P T 2
SN S 2
G A IN
SN S 1
7
5
6