QT112-IS Atmel, QT112-IS Datasheet - Page 5

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

Specifications of QT112-IS

• 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: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Output Type: Logic
• Interface: 2-Wire
• Input Type: Logic
• Package / Case: -
• Other names: 427-1008

5.5 DC SPECIFICATIONS
Note 1: All percentage thresholds have been eliminated and replaced with a fixed threshold w.r.t. reference level
Note 2: Sensitivity depends on value of Cx and Cs. Refer to Charts 1, 2.
Piezo Driver Note
The piezo acoustic driver has been removed, as the duration required to operate the beeper would interfere with
the sensing interval and slow down the device.
Sensitivity Adjustment Note
The device has a fixed threshold point of 6 counts of deviation. Gain pin adjustment (pin 5) has been eliminated
and replaced with a strap option for Master / Slave mode:
The sensitivity of the circuit is governed by the relative sizes of Cs and Cx. A detection is made if the signal rises
by 6 counts from the reference level; this amount, unlike the QT110, is not ratiometric to the signal level and
therefore the sensitivity can be altered by simply changing Cs. To provide a consistent level of sensitivity, only
stable types of capacitors are recommended for Cs, such as NPO, C0G, PPS film, and certain types of
polycarbonate when used over normal room temperature ranges.
Larger values of Cs will make the sensor more sensitive, while larger amounts of Cx will desensitize it (see
Charts 1, 2). Minimizing stray Cx is crucial if high levels of sensitivity are desired. By using values of Cs around
0.47uF (470nF), proximity distances of several centimeters can easily be obtained from small electrodes.
Pin Functions
The QT115 pins are defined as shown:
QT113 QProx™ 8-pin Sensor
Parameter
I
I
DD
DD
S
PIN
NOTE: It is extremely important to maintain stable levels of Vdd, as the supply is used as a
reference. Minor fluctuations in Vdd WILL cause false triggers or rapid swings in gain. DO NOT use
bench power supplies or supply circuits shared with other digital functions. Ordinary 78L05 class
regulators are fine in almost all cases. The QT115 is an extremely sensitive device... do not take
power supply issues lightly.
1
2
3
4
5
6
7
8
Supply current, master mode
Supply current, slave mode
Sensitivity range
Function
Vdd
Out
Sync Pulse Out (master or slave mode)
Sync Pulse In (slave mode only)
Master/Slave select
SNS1
SNS2
Gnd
Description
VDD = 3.0V, CS = 10NF, CX = 10PF, TA = RECOMMENDED RANGE
Table 1-1 Master/Slave Strap Options
Table 2-1 QT115 Pin Functions
Mode
Master
Slave
1,000
Min
Typ
700
60
-
Description
Power, +3V to +5V
Active-low output
20us nominal negative sync pulse
>10us, <50us negative pulse input to trigger in slave mode
In Master Mode: Connect to either Gnd or Vcc.
Vdd = Master mode, Gnd = Slave mode (strap option)
QT Sense pin 1
QT Sense pin 2
Ground, 0V
Max
28
Tie Pin 5 to:
Gnd
Vdd
Units
µA
µA
fF
Cs = 10nF to 100nF
Cs = 10nF to 100nF
Typical, see figs 1, 2; Note 1, 2
Notes
© 1999 QRG Ltd.