QT112-D - Atmel - Datasheet.Directory

QT11x VARIATIONS

4 August 2004

Variable gain, daisy-chainingQT115

Faster response timeQT112

Longer recalibration timeoutsQT111

QT111-I / QT111H-I QProx™ 8-pin Sensor

See QT110 datasheet for primary information. This sheet only lists differences with the QT110.

This part is only available in -I suffix (-40..+85C)

Description

The QT111 is a touch sensor IC having recalibration timeouts (“max on-duration”) of 5 minutes and infinity. This

allows the device to be used in situations where recalibration timeouts are not desired, for example in certain

consumer, machine tool and process control applications where continuous touch over long periods is desired,

like hand-on-joystick sensors, dead-man switches, etc. Although the primary application of the device is still as a

‘touch sensor’, longer timeouts also aknowledge alternate uses for the QT110 family, for example in process

controls.

Differences with QT110

The QT111 sensor is exactly the same in all respects to the QT110 with the following exceptions shown in bold

(refer to Table 2-1 in the QT110 datasheet):

300s

VddGnd

Pulse

300s

GndGnd

Toggle

infinite

GndVdd

DC Out

300s

VddVdd

DC Out

Max On-

Duration

Tie

Pin 4 to:

Tie

Pin 3 to:

Table 2-1 Output Mode Strap Options

All other operating modes, specifications, and wiring should be read from the QT110 data sheet.

QT111H Version

The QT111H version is the same as the QT111 except has an active-high output.

Cautionary Notes

Care should be taken in infinite timeout mode that the Cs and Cx capacitances and the Vcc supply do

not drift substantially over the course of a detection; if any of these parameters change sufficiently

during the course of an active detection (remember: drift compensation is never performed during a

detection event) the sensor can either ‘stick on’ after the detected object is removed, or, the QT110’s

apparent sensitivity will be substantially reduced for a period of time until drift compensation can

recover the proper reference level. If possible, uses the lowest gain setting when using with long

timeouts.

If the sensor ‘sticks on’ after the detected object or substance is removed from the sense element, the

only way to clear the sensor may be to remove power momentarily in order to induce a full

recalibration.

Package Marking - QT111-I

DIP Package: DIP devices are marked 'QT111'

SO8 Package: Marked 'QT1 Y'

Package Marking - QT111H-I

DIP Package: Not offered

SO8 Package: Marked 'QT1 C'

Quantum Research Group Ltd. 4 August 2004

QT112-I / QT112H-I QProx™ 8-pin Sensor

See QT110 datasheet for primary information. This sheet only lists differences with the QT110.

This part is only available in -I suffix (-40..+85C)

Description

The QT112 is a variant of the QT110 having a faster response time of 49ms worst case, and 25ms typical. It is

designed for those touch sensing applications where faster speed is paramount, for example in games and toys

where rapid reaction time is critical, or in machine tool controls where speed is important. It trades off power

consumption for speed. Also, note that the device has a consensus filter count 2 instead of 4, and does not have

an acoustic driver for a piezo 'beeper'.

Differences with the QT110

The QT112 sensor is exactly the same in all respects to the QT110 with the following exceptions (refer to Tables

4.3, 4.4, and 4.5 in the QT110 datasheet):

4.3 AC SPECIFICATIONS

Vdd = 3.0, Ta = recommended operating range

ms49Response timeT

ms24Burst spacing intervalT

Notes

UnitsMaxTypMinDescription

Parameter

4.4 SIGNAL PROCESSING

ms/level24Negative drift compensation rate

ms/level1,250Positive drift compensation rate

samples2Consensus filter length

Notes

UnitsMax

Typ

MinDescription

4.5 DC SPECIFICATIONS

Vdd = 3.0V, Cs = 10nF, Cx = 5pF, Ta = recommended range, unless otherwise noted

µA60Supply currentI

Notes

UnitsMaxTypMinDescription

Parameter

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.

QT112H Version

The QT112H version is the same as the QT112 except with an active-high output.

All other operating modes, specifications, and wiring should be taken from the QT110 data sheet.

Package Marking - QT112-I

DIP Package: DIP devices are marked 'QT112'

SO8 Package: Marked 'QT1 2I'

Package Marking - QT112H-I

DIP Package: DIP devices are marked 'QT112H'

SO8 Package: Marked 'QT1 M'

Quantum Research Group Ltd. 4 August 2004

QT115-I / QT115H-I QProx™ 8-pin Sensor

See QT110 datasheet for primary information. This sheet only lists differences with the QT110.

This part is only available in -I suffix (-40..+85C)

Description

The QT115 is a variant of the QT110 having variable sensitivity and the ability to daisy-chain, allowing multiple

QT115's to be used in immediate proximity to each other to create a small touch panel of up to 10 keys. Like the

QT113, it has a variable threshold which can be modified by simply altering the value of the sample capacitor Cs,

which acts to modify gain. It does not include any of the option jumpers found on the QT110 or QT113; instead it

has a single option jumper for 'Master' or 'Slave' mode operation.

The QT115 includes 'Sync Out' and 'Sync In' pins for daisy-chaining. The first IC in the chain is the Master while

the remaining devices in the chain are slaves. Daisy-chaining lets each device take its turn in generating a burst,

free from interference by the other QT devices. In Master mode the IC operates autonomously, and generates a

20us negative Sync Out pulse on pin 3 after each burst. In Slave mode the IC issues a detection burst only after

it receives a negative Sync pulse on pin 4 from a prior device in the chain, which could be another Slave or a

Master. Slave devices in turn issue a 20us Sync pulse after each burst on pin 3.

The QT115 is designed for contact and prox sensing applications where high sensitivity is paramount, for

example when sensing through thick panels or windows or for security monitoring. The QT115 trades off power

consumption for speed and sensing range. Also, note that the device has a consensus filter count of 3 instead of

4, and does not have the drive capability for a piezo 'beeper'.

If desired, the Master device can be eliminated and the chain of Slave devices can be mastered from an external

pulse source of 20us negative pulses at the desired repetition rate. This potentially allows for faster operation.

Differences with the QT110

The QT115 IC is exactly the same in all respects to the QT110 with the following exceptions (refer to Tables 5.2,

5.3, 5.4, and 5.5 in the QT110 datasheet).

5.2 RECOMMENDED OPERATING CONDITIONS

Cx Load Capacitance...................................................................... 0 to 100pF

Cs................................................................................... 10nF to 500nF

5.3 AC SPECIFICATIONS

VDD = 3.0, TA = RECOMMENDED OPERATING RANGE

Note 1ms3008Response timeT

Cs = 10nf to 500nf, Cx = 0ms750.5Burst lengthT

Cs = 10nf, Cx = 0ms2Burst spacing interval, slaveT

Cs = 10nf to 500nf, Cx = 0ms4030Burst spacing interval, masterT

Notes

UnitsMaxTypMinDescription

Parameter

Note 1: Lengthens with increasing Cs but decreases with increasing Cx; see Chart 3.

5.4 SIGNAL PROCESSING

secs10Post-detection recalibration timer duration

ms/level40Negative drift compensation rate

ms/level1,800Positive drift compensation rate

samples3Consensus filter length

w.r.t. threshold cts.%17Hysteresis

Note 1counts6Threshold differential, fixed

Notes

UnitsMax

Typ

MinDescription

Note 1: All percentage thresholds have been eliminated and replaced with a fixed threshold w.r.t. the reference level

Quantum Research Group Ltd. 4 August 2004

5.5 DC SPECIFICATIONS

VDD = 3.0V, CS = 10NF, CX = 10PF, TA = RECOMMENDED RANGE

Typical, see figs 1, 2; Note 1, 2fF28-1,000Sensitivity rangeS

Cs = 10nF to 100nFµA700Supply current, slave modeI

Cs = 10nF to 100nFµA60Supply current, master modeI

Notes

UnitsMaxTypMinDescription

Parameter

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:

GndSlave

VddMaster

Tie Pin 5 to:Mode

Table 1-1 Master/Slave Strap Options

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.

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.

Pin Functions

The QT115 pins are defined as shown:

Ground, 0VGnd8

QT Sense pin 2SNS27

QT Sense pin 1SNS16

Vdd = Master mode, Gnd = Slave mode (strap option)Master/Slave select5

>10us, <50us negative pulse input to trigger in slave mode

In Master Mode: Connect to either Gnd or Vcc.

Sync Pulse In (slave mode only)4

20us nominal negative sync pulseSync Pulse Out (master or slave mode)3

Active-low outputOut2

Power, +3V to +5VVdd1

DescriptionFunctionPIN

Table 2-1 QT115 Pin Functions

Quantum Research Group Ltd. 4 August 2004

Calibration and Drift Compensation

Calibration and drift compensation operate similarly to the QT110. With large values of Cs and small values of

Cx, drift compensation will appear to operate more slowly than with the reverse.

Note that the positive and

negative drift compensation rates are different; the sensor will compensate more quickly for the removal of an

object than it will to the introduction of an object.

The QT115 uses a fixed recalibration timeout of 10 seconds.

Response Time

The QT115's response time is entirely dependent on the burst rate. In Master mode the nominal burst rate is

40ms, and 3 successive bursts are required to confirm a detection, giving a nominal 120ms response time.

In slave mode, the burst rate and hence response time are dependent on the input sync pulse rate. Faster sync

pulse rates will lead to faster response times.

HeartBeat™ Signal

The QT115's HeartBeat pulse works exactly the same as in the QT110 except that the HeartBeat rate is the

same as the burst rate. In Master mode, the HeartBeat signal occurs just before the acquisition burst. In slave

mode, it occurs just after receipt of the slave pulse on pin 4. As with the QT110, the HB signal can be

suppressed if not wanted by a variety of simple methods.

Notes on Daisy Chaining QT115's

The QT115 is intended to be daisy-chained for the purpose of allowing each of the sensors to operate without

interference from other devices in the chain. This allows electrodes from each device to be placed immediately

adjacent the other electrodes with only the barest of gaps.

Individual devices in the chain can have unique sensitivities. QT113-style sensing allow for very high sensitivity

levels if required. One device can be used with a large metal area to create a prox detector capable of many

centimeters range, for example to activate the panel, equipment, or a light upon a mere hand-wave. The other

devices in the chain can be used to implement low-gain touch switches that must be contacted by a fingertip for

activation. The net effect of this configuration can be quite dramatic.

The only limitation is that the sum of the burst lengths, which depends on load Cx and the Cs capacitor, must not

be so long that burst of the last device in the chain overlaps the burst of the first device. Should this occur, the

first and last devices may interfere with each other if the electrodes and wiring are adjacent to each other. One

simple solution to this problem is to physically separate the traces and electrodes from devices that have

overlapping bursts.

QT115H Version

The QT115H version is the same as the QT115 except with an active-high output.

Package Marking - QT115

DIP Package: DIP devices are marked 'QT115'

SO8 Package: Marked 'QT1 H' or ‘QT115 I’

Package Marking - QT115H

DIP Package: DIP devices are marked 'QT115H'

SO8 Package: Marked 'QT1 L'

Quantum Research Group Ltd. 4 August 2004