QT113A-ISG Atmel, QT113A-ISG Datasheet - Page 5

• Manufacturer Part Number: QT113A-ISG
• Description: IC SENSOR TOUCH/PROX 1CHAN 8SOIC
• Manufacturer: Atmel
• Series: QProx™r
• Type: Capacitiver

Specifications of QT113A-ISG

• Touch Panel Interface: 1, 2-Wire
• Number Of Inputs/keys: 1 Key
• Resolution (bits): 9, 14 b
• Data Interface: Serial
• Voltage Reference: Internal
• Voltage - Supply: 2 V ~ 5.25 V
• Current - Supply: 600µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Output Type: Logic
• Input Type: Logic
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Other names: 427-1138-2

2.1.5 F
The QT113 has no recalibration pin; a forced recalibration is
accomplished only when the device is powered up. However,
supply drain is low so it is a simple matter to treat the entire
IC as a controllable load; simply driving the QT113's Vdd pin
directly from another logic gate or a microcontroller port
(Figure 2-2) will serve as both power and 'forced recal'. The
source resistance of most CMOS gates and microcontrollers
are low enough to provide direct power without problem. Note
that many 8051-based micros have only a weak pullup drive
capability and will require CMOS buffering. 74HC or 74AC
series gates can directly power the QT113, as can most other
microcontrollers.
Option strap configurations are read by the QT113 only on
powerup. Configurations can only be changed by powering
the QT113 down and back up again; again, a microcontroller
can directly alter most of the configurations and cycle power
to put them in effect.
2.1.6 R
The QT113's response time is highly dependent on burst
length, which in turn is dependent on Cs and Cx (see Figures
4-1, 4-2). With increasing Cs, response time slows, while
increasing levels of Cs reduce response time. Figure 4-3
shows the typical effects of Cs and Cx on response time.
2.2 OUTPUT FEATURES
The QT113 is 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 QT113 can respond in a DC mode, where
the output is active-low upon detection. The output will
remain active-low for the duration of the detection, or until the
Max On-Duration expires (if not infinite), whichever occurs
first. If a max on-duration timeout occurs first, the sensor
performs a full recalibration and the output becomes inactive
until the next detection.
In this mode, three Max On-Duration timeouts are available:
10 seconds, 60 seconds, and infinite.
Infinite timeout is useful in applications where a prolonged
detection can occur and where the output must reflect the
detection no matter how long. In infinite timeout mode, the
designer should take care to be sure that drift in Cs, Cx, and
lQ
Figure 2-2 Powering From a CMOS Port Pin
microcontroller
ORCED
ESPONSE
CMOS
ODE
S
O
ENSOR
T
UTPUT
IME
PORT X.m
PORT X.n
R
ECALIBRATION
OUT
QT113
Vdd
Vss
0.01µF
5
Vdd do not cause the device to ‘stick on’ inadvertently even
when the target object is removed from the sense field.
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.
Max On-Duration in Toggle mode is fixed at 10 seconds.
When a timeout occurs, the sensor recalibrates but leaves
the output toggle state unchanged.
2.2.3 H
The QT113 output has a full-time HeartBeat™ ‘health’
indicator superimposed on it. This operates by taking 'Out'
into a 3-state mode for 300µs once after 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.
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 low for the duration of the detection, and no
HeartBeat pulse will be evident.
If the sensor is wired to a microcontroller as shown in Figure
2-4, the microcontroller can reconfigure the load resistor to
either ground or Vcc depending on the output state of the
QT113, so that the pulses are evident in either state.
Electromechanical devices like relays will usually ignore this
short pulse. The pulse also has too low a duty cycle to visibly
affect 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).
2.2.4 O
The QT113’s `output is active low and can sink up to 5mA of
non-inductive current. If an inductive load is used, such as a
small relay, the load should be diode clamped to prevent
damage. When set to operate in a proximity mode (at high
gain) the current should be limited to 1mA to prevent gain
shifting side effects from occurring, which happens when the
load current creates voltage drops on the die and bonding
wires; these small shifts can materially influence the signal
level to cause detection instability as described below.
Care should be taken when the QT113 and the load are both
powered from the same supply, and the supply is minimally
regulated. The QT113 derives its internal references from the
power supply, and sensitivity shifts can occur with changes in
Vdd, as happens when loads are switched on. This can
Table 2-1 Output Mode Strap Options
DC Out
DC Out
DC Out
Toggle
EART
UTPUT
OGGLE
B
EAT
D
M
RIVE
ODE
™ O
Pin 3 to:
Gnd
Gnd
Vdd
Vdd
Tie
O
UTPUT
UTPUT
Pin 4 to:
Gnd
Gnd
Vdd
Vdd
Tie
R1.05/0405
Duration
Max On-
infinite
10s
60s
10s