ATMXT154-CUI - ATMEL - Datasheet.Directory

9554E–AT42–01/13

Features

•Number of QTouch® Keys:

– 0 to 7, one slider or one wheel

•Technology:

– Patented spread-spectrum charge-transfer

•Key Outline Sizes:

– 5 mm x 5 mm or larger (panel thickness dependent); widely different sizes

and shapes possible

•Key Spacing:

– 6 mm or wider, center to center (panel thickness, human factors

dependent)

•Key Design:

– Single solid or ring shaped electrodes; wide variety of possible layouts

•Wheel Size:

– Typically 30 – 50 mm diameter, resistively interpolated wheel up to 80 mm

diameter, typical width 12 mm

•Slider Size:

– Typically 50 – 100 mm length, typical width 12 mm

•Slider/Wheel Electrode Design:

– Choice of spatially interpolated (resistorless) or resistively interpolated

design

– Slider can be an arc or other irregular shape

•Layers Required:

– One layer substrate; electrodes and components can be on same side

•Substrates:

– FR-4, low cost CEM-1 or FR-2 PCB materials; polyamide FPCB; PET films,

glass

•Electrode Materials:

– Copper, silver, carbon, ITO, virtually anything electrically conductive

•Panel materials:

– Plastic, glass, composites, painted surfaces (nonconductive paints)

•Adjacent Metal:

– Compatible with grounded metal immediately next to keys

•Panel Thickness:

– For keys, up to 15 mm glass, 10 mm plastic (key size dependent)

– For slider/wheel, up to 4 mm glass, 3 mm plastic

•Key Sensitivity:

– Adjustable via change in sampling capacitor (Cs) value

Atmel AT42QT2100

QTouch Touch Sensor IC

DATASHEET

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

•Interface:

– SPI @ 750 kHz, CHANGE and DRDY status indicator pins

•Moisture Tolerance:

– Increased moisture tolerance based on hardware design and firmware tuning

•Power:

– 2.0 V to 5.5 V

•Signal Processing:

– Self-calibration, autodrift compensation, noise filtering, patented Adjacent Key Suppression® (AKS®)

•Package:

– 32-pin 5 x 5 mm MLF RoHS compliant

– 32-pin 7 x 7 mm TQFP RoHS compliant

•Applications:

– Portable devices, domestic appliances and A/V equipment, PC peripherals, office equipment

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

1. Pinout and Schematic

1.1 Pinout Configuration

1.2 Pin Descriptions

SNSB2

SNSKB

SNSB1

RESET

SNSKA2

SNSA2

SNSKA3

SNSKB5

SNSKB6

SNSKB7

SNSB7

MOSI

MISO

SNSKB2

SNSB3

SNSKB3

VDD

VSS

SNSKB4

SNSB5 SCK

VDD

DRDY

CHANGE

VSS

SPREAD

SNSA1

SNSKA1

817

32 31 30 29 28 27 26 25

910 11 16

SNSB6

SNSB4

SNSA3

QT2100

Table 1-1. Pin Listing

Pin Name Type Function If Unused, Connect To...

1SNSKB2 I/O Sense pin. Connect to any CsB + Key Open

2SNSB3 (1) I/O Sense pin. Connect to CsB3 Open

3SNSKB3 I/O Sense pin. Connect to any CsB + Key Open

4VDD PPower -

5VSS PGround -

6SNSKB4 I/O Sense pin. Connect to any CsB + Key Open

7SNSB4 (1) I/O Sense pin. Connect to CsB4 Open

8SNSB5 (1) I/O Sense pin. Connect to CsB5 Open

9SNSKB5 I/O Sense pin. Connect to any CsB + Key Open

10 SNSKB6 I/O Sense pin. Connect to any CsB + Key Open

11 SNSKB7 I/O Sense pin. Connect to any CsB + Key Open

12 SNSB6 (1) I/O Sense pin. Connect to CsB6 Open

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I/O CMOS input/output

I CMOS input only

OD CMOS open drain output (pull-up to Vdd)

OF CMOS output that can float during Reset, Sleep or LP modes

P Ground or power

13 SNSB7 (1) I/O Sense pin. Connect to CsB7 Open

14 SS ISPI Slave Select (active low) -

15 MOSI ISPI Master Out /Sl ave In -

16 MISO OF SPI Master In/Se ri al Out -

17 SCK ISPI Clock -

18 VDD PPower -

19 DRDY OF SPI Data Ready handshake line Open

20 CHANGE OF St ate change notification Open

21 VSS PGround -

22 SPREAD OD Spread-spectrum drive

Connect to Vdd (high) to enable

Connect to Vss (low) to disable -

23 SNSA1 (1) I/O Sense pin. Connect to CsA1 Open

24 SNSKA1 I/O Sense pin. Connect to any CsA + slider/wheel Open

25 SNSA2 (1) I/O Sense pin. Connect to CsA2 Open

26 SNSKA2 I/O Sense pin. Connect to any CsA + slider/wheel Open

27 SNSA3 (1) I/O Sense pin. Connect to CsA3 Open

28 SNSKA3 I/O Sense pin. Connect to any CsA + slider/wheel Open

29 RESET IReset (active low) Vdd via resistor

30 SNSB1 (1) I/O Sense pin. Connect to CsB1 Open

31 SNSKB1 I/O Sense pin. Connect to any CsB + Key Open

32 SNSB2 (1) I/O Sense pin. Connect to CsB2 Open

1. SNS terminals can be paired with any SNSK terminals of the same group. For example, SNSA1 can be paired with

any SNSKA terminal.

Table 1-1. Pin Listing (Continued)

Pin Name Type Function If Unused, Co nn ect To...

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1.3 Schematic

Figure 1-1. Connection Diagram (32-MLF Package)

Important Design Guidelines:

The sensitivities of the various sense channels are determined by the values of the respective Cs capacitors

(that is, CsB1, CsB7, and so on); these values will require adjustment based on building a prototype product

and testing the sensitivity experimentally.

Signals DRDY and CHANGE may need pull-down resistors.

Re Figure 1-1, check the following sections for the variable component values:

Section 3.1 on page 9: Cs capacitors (CsB)

Section 3.2 on page 9: Sample resistors (RSNS)

Section 3.3 on page 9: Voltage levels

SNSKB2 1

SNSB3 2

SNSKB5 9

SNSB5 8

SNSKB7 11

SNSKB4 6

SNSKB3 3

SNSB7 13

SNSKB6 10

SNSB6 12

SNSB1 30

SPREAD

SNSKB1 31

DRDY

SNSB2 32

SNSB4 7

SNSA2 25

SNSKA1 24

SNSA1 23

CHANGE

SCK

MISO

SNSA3 27

SNSKA3 28

SNSKA2 26

RESET

MOSI

VDD 4

VDD 18

VSS

GND

Vin

GND

Vout

Voltage Regulator

VCC VDD

GND

C3 C4C2C1

VDD

MOSI

MISO

SCK

DRDY

CHANGE

GND

QT Key

Key B1

QT Key

Key B2

QT Key

Key B3

QT Key

Key B4

QT Key

Key B5

QT Key

Key B6

QT Key

Key B7

RsB1

RsB2

RsB3

RsB4

RsB5

RsB6

RsB7

RsA1

RsA2

RsA3

R2 R3

R4 R5

Ch1

Ch2

Ch3

Wheel/Slider

CsB1

CsB2

CsB3

CsB4

CsB5

CsB6

CsB7

CsA1

CsA2

CsA3

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2. Overview

2.1 Introduction

The AT42QT2100 (QT2100) is an easy-to-use sensor IC based on the Atmel-patented charge-transfer (QT™)

principles for robust operation and ease of design. This device has many advanced features which provide for

reliable, trouble-free operation over the life of the product. In particular the QT2100 features advanced self-

calibration, drift compensation, and fast thermal tracking. The QT2100 can tolerate some fluctuations in the power

supply, and in many applications will not require a dedicated voltage regulator.

The QT2100 is capable of detecting near-proximity or touch on up to seven electrodes and a slider/wheel. It allows

electrodes to project sense fields through any dielectric such as glass or plastic. These electrodes are laid out as a

scroller (slider or wheel), plus seven additional independent keys.

Each key channel can be tuned for a unique sensitivity level by simply changing a corresponding external Cs

capacitor, whereas the slider/wheel sensitivity can be changed dynamically through SPI commands. Any number of

key channels can be optimized for operation as hand proximity sensors by increasing the sensitivity for the

corresponding channel.

Note: There are special conditions if using AKS (see Section 4.3.6 on page 15).

The slider/wheel uses a simple, inexpensive sensing element between three connection points. The QT2100 can

report a single rapid touch anywhere along the sense elements, or it can track a finger moving along the

slider/wheel's surface in real time.

By using the charge-transfer principle, this device delivers a level of performance clearly superior to older

technologies yet is highly cost-effective. Spread-spectrum burst technology provides superior noise rejection.

2.2 Burst Operation

The device operates in burst mode. Each key is acquired using a burst of charge-transfer sensing pulses whose

count varies depending on the value of the sense capacitors (CsA1 to CSA3 and CsB1 to CSB7) and the load

capacitance Cx (finger touch capacitance and circuit stray capacitance).

The channels’ signals are acquired using three successive bursts of pulses:

Burst 1: B1, B2, B3

Burst 2: B4, B5, B6, B7

Burst 3: A1, A2, A3

where B1 to B7 are the individual key sensors and A1 to A3 are the slider/wheel sensors.

Bursts operate in sequence and occur one after the other with minimum delay. During each burst the DRDY pin is

held low. The groups are separated by an interval of 500 µs when DRDY is held high to signal an appropriate time for

SPI communications. Communications may be carried out at any time, however, regardless of the state of the DRDY

pin.

2.3 User Interface Layout and Options

The QT2100 can sense through all common plastics or glass or other dielectric materials up to 10 mm thick. It can be

used to implement a linear slider or rotary scroll wheel plus seven additional discrete keys. The slider or wheel

indicates absolute positions.

2.4 Slider and Wheel Construction

The QT2100 can be connected to a linear slider element (see Section 3.5 on page 10) or a wheel. Selection of linear

operation or wheel is set through an SPI command.

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2.5 Proximity Effect

Any number of keys can be programmed to have hand or body proximity. By using a rela tively large ele ctrode inside

the product enclosure and a larger value of CsB, the product can auto power up or activate its display with hand

approach. This simple feature can add enormous sales appeal to almost any product.However, if using AKS see

Section 4.3.6 on page 15.

2.6 Moisture Tolerance

The presence of water (condensation, sweat, spilt water, and so on) on a sensor can alter the signal values

measured and thereby affect the performance of any capacitive device. The moisture tolerance of QTouch devices

can be improved by designing the hardware and fine-tuning the firmware following the recommendations in the

application note Atmel AVR3002: Moisture Tolerant QTouch Design (www.atmel.com/Images/doc42017.pdf).

2.7 SPI Interface

The QT2100 is an SPI slave mode device, utilizing a four-wire full-duplex SPI interface.

In addition to the standard four SPI signals (SS, SCK, MOSI and MISO), there is a DRDY (data ready) output which

may optionally be used to time communications such that they do not occur during channel measurement bursts.

During each burst DRDY is held low by the QT2100. After each group burst, DRDY is driven high for 500 µs or until

3 bytes have been exchanged.

The QT2100 also provides a CHANGE signal to indicate when there has been a change in detection state. This

removes the need for the host to poll the QT2100 continuously.

On each SPI transfer the host sends three bytes to the QT2100 and the QT2100 simultaneously sends three bytes to

the host. The bytes sent from the host provide the QT2100 with all its configuration information; the bytes sent from

the QT2100 convey the states of the touch keys and slider or wheel.

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2.8 Operating Modes

The device features a number of operating modes to set the current drain and speed of response.

The available operating modes are:

Free Run Mode

This mode uses a continuous stream of acquire bursts. Free Run mode has, in consequence, the highest

power drain of all the QT2100 operating modes but the fastest response time.

LP Mode

In LP (low power) modes, the QT2100 spends a portion of the time sleeping to conserve power; it wakes

itself periodically to perform acquire bursts, then normally goes back to sleep again. The QT2100 provides

a choice of intervals between acquire bursts to allow an appropriate trade-off between speed and power to

be made for each product.

Sleep Mode

In Sleep mode, the QT2100 shuts down to conserve power; it remains in this mode, carrying out no

acquisition bursts until the host wakes it using the SS pin.

Sync Mode

In this mode the device synchronizes to the host in a way that allows for the suppression of heavy low

frequency noise; for example, from mains frequencies and their harmonics.

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3. Wiring and Parts

3.1 Cs Sample Capacitors

The Cs (CsA1 to CSA3 and CsB1 to CSB7) sample capacitors accumulate the charge from the key electrodes and

determine sensitivity. Higher values of Cs make the corresponding sensing chan nel more sensitive. The values of Cs

can differ for each channel, permitting differences in sensitivity from key to key or to balance unequal sensitivities.

Unequal sensitivities can occur due to key size and placement differences and stray wiring capacitances. More stray

capacitance on a sense trace will desensitize the corresponding key; increasing the Cs for that key will compensate

for the loss of sensitivity.

The Cs capacitors can be virtually any plastic film or low to medium-K ceramic capacitor. Acceptable capacitor types

for most uses include PPS film, polypropylene film, and NP0 and X7R ceramics. Lower grade ceramics than X7R are

not advised; the X5R grade should be avoided because it is less stable than X7R. Larger values of Cs require better

quality to ensure reliable sensing

The normal Cs range is 1 nF to 100 nF for the keys and 4.7 nF to 220 nF for each channel of the slider or wheel for

good performance and position detection. The actual value used depends on the sensitivity required. A 3 nF to 5 nF

capacitor is typical for a touch key with an electrode diameter of 10 to 12 mm and a cover of 1 to 2 mm plastic, and

approximately 10 nF to 15 nF for slider or wheel electrodes.

3.2 Rs Series Resistors

Series Rs resistors (RsA1 to RSA3 and RsB1 to RSB7) are in-line with the electrode connections and are used to

limit electrostatic discharge (ESD) currents and to suppress radio frequency interference (RFI). For most

applications the Rs resistors will be in the range 4.7 k to 33 k each. In a few applications with low loading on the

sense keys the value may be up to 100 k.

Although these resistors may be omitted, the device may become susceptible to external noise or RFI. For details of

how to select these resistors refer to Application Note QTAN0079 Buttons, Sliders and Wheels Sensor Design

Guide.

3.3 Power Supply

The power supply can range from 2.0 V to 5.5 V. If this fluctuates slowly with temperature, the device will track and

compensate for these changes automatically with only minor changes in sensitivity. If the supply voltage drifts or

shifts quickly, the drift compensation mechanism will not be able to keep up, causing sensitivity anomalies or false

detections. In this situation a dedicated voltage regulator should be included in the circuit.

The QT2100 power supply should be locally regulated using a three-terminal device, to between 2.0 V and 5.5 V. If

the supply is shared with another electronic system, care should be taken to ensure that the supply is free of digital

spikes, sags, and surges, all of which can cause adverse effects.

For proper operation a 0.1 µF, or greater, bypass capacitor must be used between Vdd and Vss; the bypass

capacitor should be routed with very short tracks to the QT2100 VSS and VDD pins.

3.4 MLF Package Restrictions

The central pad on the underside of the MLF chip should be connected to ground. Do not run any tracks underneath

the body of the chip, only ground. Figure 3-1 shows an example of good and bad tracking.

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Figure 3-1. Examples of Good and Bad Tracking

3.5 Slider and Wheel Construction

The QT2100 can be connected to a linear slider element or a wheel (see Figure 3-2). Selection of linear slider

operation or a wheel is set through an SPI command.

As with touch button electrodes, sliders and wheels can be constructed as etched areas on a PCB or flex circuit, or

from clear conductors such as Indium Tin Oxide (ITO) or screenprinted PEDOT to allow backlighting effects, or for

use over an LCD display.

Figure 3-2. All-Metal Slider and Wheel Construction

(Downloadable CAD files can be found on the A tmel website)

3.6 Oscillator

No external oscillator is needed.

3.7 PCB Layout and Construction

Refer to Application Note QTAN0079, Buttons, Sliders and Wheels Sensor Design Guide and the Touch Sensors

Design Guide (both downloadable from the Atmel website), for more information on construction and design

methods.

The sensing channels used for the individual keys can be implemented as per the Touch Sensors Design Guide.

Example of GOOD tracking Example of BAD tracking

127

1 to 126

Position (at 7 bits: 0 to 127)

SNSA1

Tips of triangles should

be spaced 4 mm apart.

4 mm

Position 0

Position 43

Position 85

SNSA2 SNSA3SNSA3

SNSA1

SNSA2

SNSA3

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3.8 PCB Cleanliness

Modern no-clean-flux is generally compatible with capacitive sensing circuits.

3.9 Spread-spectrum Circuit

The QT2100 offers the ability to spectrally spread its frequency of operation to heavily reduce susceptibility to

external noise sources and to limit RF emissions.

With this option enabled, bursts operate over a spread of frequencies, so that external fields will have minimal effect

on key operation and emissions are very weak. Spread-spectrum operation works together with the Detect Integrator

(DI) mechanism to dramatically reduce the probability of false detection due to noise.

Spread spectrum may be enabled by connecting the SPREAD pin to Vdd via a pull-up resistor, or disabled by

connecting to Vss via a pull-down resistor.

CAUTION: If a PCB is reworked to correct soldering faults relating to the QT2100, or to

any associated traces or components, be sure that you fully understand the nature of the

flux used during the rework process. Leakage currents from hygroscopic ionic residues

can stop capacitive sensors from functioning. If you have any doubts, a thorough

cleaning after rework may be the only safe option.

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4. Detailed Operation

4.1 Reset

4.1.1 Introduction

When starting from power-up or RESET reset there are a few additional factors to be aware of. In most applications

the host will not need to take special action.

During hardware reset all outputs are disabled. To define the levels of the CHANGE and DRDY during reset these

signals should pulled down by resistors to 0 V. Otherwise, they may drift high causing the host to detect a false

logic 1.

When the initial reset phase ends, CHANGE and DRDY outputs are enabled. DRDY will drive low and CHANGE will

drive high.

4.1.2 Delay to SPI Functionality

The QT2100 SPI interface is not operational while the device is being reset. However, SPI is ma de operation al early

in the start-up procedure.

After any reset (either via the RESET pin or via power-up), SPI typically becomes operational within 50 ms of RESET

going high or power-up. CHANGE is pulled high, and held high until the device status is read by the host micro-

controller, to indicate completion of the initialization sequence after power-on or reset.

4.1.3 Reset Delay to Touch Detection

After power-up or reset, the QT2100 calibrates all electrodes.

During this time, touch detection cannot be reported. Calibration completes after 15 burst cycles, which takes

approximately 350 ms, depending on the electrode layout and Cs selection.

In total, 400 ms are required from reset or power-up for the device to be fully functional.

4.1.4 Disabled Keys:

Keys with missing Cs capacitors, or that otherwise have an out-of-range signal during calibration, are considered to

be unused or faulty and are disabled. Disabled keys are re-examined for operation after each reset or recalibration

event.

4.1.5 Mode Setting After Reset

After a reset the device will enter Free Run mode, with AKS disabled.

4.2 Communications

4.2.1 Introduction

The QT2100 communicates as a slave device over a full-duplex 4-wire (MISO, MOSI, SCK, SS) SPI interface. In

addition there is a DRDY pin which indicates when the QT2100 is carrying out acquisition bursts and a CHANGE pin

which is asserted when a change occurs in the status of the touch sensors (see Table 4-1).

Table 4-1. Additional Pins

Pin High Low

DRDY Burst is complete Burst is active

CHANGE New touch data Latest data has already been

read by host

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See Section 6.5 on page 32 for details of the SPI Configuration and Timing Parameters.

The host must always transfer three bytes in succession within the allotted time (10 ms maximum). If all bytes are

not received in this interval it is treated by the QT2100 as an error. In this case the exchange is reset and the next

read will contain the first data byte of a new exchange.

Messages from the host to the QT2100 carry configuration information; return data from the QT2100 carries key

state information. For details of the message contents see Section 5. on page 19.

Figure 6-1 and Figure 6-2 on page 33 show the basic timing for SPI operation. The host does the clocking and

controls the timing of the transfers from the QT2100. Transfers are always clocked as a set of three bytes, Byte 1, 2,

and 3.

DRDY stays high for 500 µs. It falls again after Byte 3 has shifted to indicate completion. DRDY goes high after each

burst.

After the host asserts SS low, it should wait >22 µs in low power mode before starting SCK; in Free run mode, a

delay of 2 µs is sufficient. The QT2100 reads the MOSI pin with each rising edge of SCK, and shifts data out on the

MISO pin on falling edges. The host should do the same to ensure proper operation.

Between the end of the Byte 1 shift and the start of the Byte 2 shift (and between Byte 2 and Byte 3), the host may

raise SS again, but this is not required. SS should be he ld high when not communicating; if SS is low this is taken as

an indication of impending communications.

In this case, extra current is drawn, as the QT2100 does not enter its lowest power sleep mode.

All timings not mentioned above should be as in Figure 6-2 on page 33.

4.2.2 Change Pin

The QT2100 has a CHANGE output pin which allows for key state change notification. Use of the CHANGE signal

relieves the host of the burden of regularly polling the QT2100 to get key states. CHANGE goes high when an event

occurs that causes a change to the contents of the Normal Data bytes; that is, when a new key is pressed, or

released, or a movement is detected on the slider/wheel.

Similarly, when a custom threshold or LPM is sent to the QT2100, the CHANGE line is asserted to indicate that the

new setting has been applied and is shown in the Normal Exchange data.

CHANGE also goes high after a reset to indicate to the host that it should do an SPI transfer in order to provide initial

configuration information to the QT2100 (as it does on every SPI transfer).

CHANGE is driven low only once the data has been read through an SPI transfer.

In the case of a transient touch on one of the sensors, in which the touch has been removed before the host has read

the status of the sensors, the Change line remains asserted.

Note: In this case the data that will be read may be identical to the data that was previously read.

4.2.3 DRDY Pin

The Data Ready (DRDY) pin is a quick indication of the QT2100 activity. During channel acquisition bursts the pin is

held low by the device, and driven high for ~500 µs in between bursts. During processing and sleep the pin is driven

high continuously, unless a 3-byte communications exchange has taken place since the last acquisition burst.

After a 3-byte exchange has completed the pin is pulled low and remains low until the next burst completion, after

which the normal cycle resumes. This allows the host to detect if the 3-byte exchange packets have become

de-synchronized.

The QT2100 has a DRDY grace period. If communications start during the 20 µs after DRDY has been deasserted

(pulled low) by the QT2100, then DRDY is reasserted and held high until the exchange is complete. Key

measurement bursts do not take place during this time.

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Figure 4-1. DRDY Cycle without Communications

Figure 4-2. DRDY Cycle with Communications

4.3 Signal Processing

4.3.1 Power-up Self-calibration

On power-up, or after reset, all 10 channels are typically calibrated and operational within 350 ms.

4.3.2 Drif t Compensation

This operates to correct the reference level of each key automatically over time; it suppresses false detections

caused by changes in temperature, humidity, dirt and other environmental effects.

The QT2100 drifts towards touch at a rate limited to 1 count every 3 seconds, and away from touch at a rate limited

to 1 count every 0.5 s. Reference drift is paused during touch detection, and for 2 s after touch detection ends. These

timings may be slower in Sync mode, or where asynchronous acquisition is triggered with LPB, as timing calculations

are derived from the acquisition interval.

Burst 1 Burst 1Burst 2 Burst 2Burst 3 Burst 3

Processing

& Sleep

DRDY

Burst 1

Burst 2

Burst 3

Burst 1 Burst 1Burst 2 Burst 2Burst 3 Burst 3

Processing

& Sleep

SCK

DRDY

Burst 1

Burst 2

Burst 3

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4.3.3 Detection Integrator Filte r

Detect Integrator (DI) filter confirmation reduces the effects of noise on key states. The DI mechanism requires a

specified number of measurements that qualify as detections (and these must occur in a row) or the detection will not

be reported.

In a similar manner, the end of a touch (loss of signal) also has to be confirmed over several measurements.

The QT2100 provides a choice of either two or six DI measurements.

4.3.4 Adjacent Key Suppression (AKS)

This patented feature works to prevent multiple keys from incorrectly responding to a single touch. This can happen

with closely spaced keys, or a scroll wheel that has buttons very near.

Adjacent Key Suppression (AKS) operates by comparing signal strengths from keys within a group of keys to

suppress touch detections from those that have a weaker signal change than the dominant one.

When enabled globally on the QT2100, AKS allows only one key or the scroll section to indicate a touch at a time.

The QT2100 has a range of preset AKS groupings, where only one key in an AKS group can indicate a touch at any

time while keys in different groups can indicate touch in any combination.

AKS can also be disabled.

4.3.5 Autorecalibration (MOD)

The device can time out and recalibrate all sensors after a continuous touch detection that lasts for the chosen

Maximum On Duration (MOD). This ensures that a key can never become stuck on due to foreign objects or other

external influences. After recalibration the key will resume normal functionality.

The nominal delay is selectable to be 10 s, 20 s, 60 s, or infinite (disabled) though the actual delay is different in

Sleep mode, as timing is entirely driven by host communications.

The device also automatically recalibrates a key when its associated signal reflects a sufficient decrease in

capacitance from the reference level (signal error). In this case, unlike MOD recalibration, only the key that shows a

signal error is recalibrated.

This recalibration is triggered when the decrease in capacitance is seen on the key signal for more than 1.5 s.

4.3.6 Proximity Sensor

Any key can be optimized for operation as a hand proximity sensor. The sensitivity can be increased by a higher

value of Cs.

However, If using AKS only channel seven can be used as a proximity sensor and the AKS bits should be set to 101,

to ensure that the proximity key does not lock out other keys or the slider/wheel (see Table 5-2 on page 20).

Design of proximity electrodes requires care, so as to ensure that the electrode area is maximized whilst ensuring

adequate and easy coupling to a hand as it approaches the equipment.

4.3.7 Faulty and Unused Keys

Any sense channel that does not have its sense capacitor (Cs) fitted is assumed to be either faulty or unused. A

sensor fault is detected by an out-of-range signal count during calibration, where the minimum allowed signal is 32

counts and the maximum is 8192. This channel takes no further part in operation unless a host-commanded

recalibration operation shows it to have an in-range burst count again.

This is important for sense channels that have an open or short circuit fault across Cs. Such channels would

otherwise cause very long acquire bursts, and in consequence would slow the operation of the device. Note that

acquisition pulses will still be generated on these channels, but no measurements of their state will be carried out.

The burst will finish when all the enabled channels on the burst group have completed acquisition.

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4.4 Operating Modes

4.4.1 Introduction

Four basic operating modes are possible: Free Run, Low Power (LP), Sleep and Sync. Sleep is a special case of

LP mode, where the sleep time is infinite. Sync is a special case of LP mode where the timing of host

communications is used as the timing basis for the QT2100 acquisition cycle. In the absence of host

communications, the device operates in its most power-efficient low power mode, LP Mode 4. See below for further

details.

4.4.2 Free Run Mode

In this mode the device operates continuously with short intervals between burst groups; there are three bursts, one

burst for each electrode group. DRDY goes high for approximately 500 µs between bursts and stays high during

signal processing.

In this mode, the acquisition bursts are unsynchronized, making this mode unsuitable if synchronization to mains

frequency is needed.

4.4.3 Low Power Mode

LP mode is designed to allow low power operation while still retaining full operation but at a slower speed. This mode

is useful for devices that must use the touch keys to wake up a product, yet minimize power consumption.

Several LP timings allow the user to trade power versus response time: the slower the response time, the lower the

power consumed.

In LP mode, the device spends a portion of the time sleeping between bursts; it wakes periodically to measure all

channels with a set of three acquisition bursts, then goes back to sleep.

If a touch is detected, the device operates as in Free Run mode and attempts to perform the Detect Integrator (DI)

noise filter function to completion; if the DI filter fails to confirm a detection the device goes back to sleep and

resumes LP mode. During the DI function the LPS bit will be cleared.

If a key is found to be in detection the CHANGE pin will go high and the part will remain in Free Run mode. To go

back into LP mode the host has to request LP mode again with an SPI communications exchange after the touch

detection has been cleared by removal of touch or recalibration.

CHANGE Pin in LP Mode: During the sleep portion of LP mode, CHANGE is held low.

If however a change of key state is confirmed, CHANGE goes high and the part runs from then on in Free Run mode

until the host reads the key state and puts the device back into LP mode or some other mode.

MISO in LP Mode: During the sleep portion of LP mode, MISO floats.

DRDY during LP Mode: DRDY remains high while the QT2100 is sleeping, to indicate to the host that SPI

communications are possible. During an actual acquire burst, DRDY is held low.

Command During LP Mode: The device can be woken from sleep by the SS pin be ing pulled low. Note that the SS

pin must be pulled high in order for the device to enter its lowest power sleep mode. If SS is held low, the device

enters a higher power sleep mode to enable SPI communications. The host may perform a normal SPI transfer as

shown in Figure 4-3 on page 17.

AT42QT2100 [DATASHEET]

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After the SPI transfer is completed, the QT2100 will generate a set of three acquire bursts if LPB = 1, during which

DRDY will be low.

The mode and options settings sent from the host to the QT2100 during the SPI transfer take effect after the set of

acquire bursts.

If either LP mode or Sleep mode is selected, the QT2100 will go back to sleep with DRDY high provided no

key is detected as possibly touched.

If Sync mode is selected, the QT2100 will go back to sleep with DRDY high provided no key is detected as

possibly touched.

The CHANGE pin will go high at this time if a key is confirmed as touched.

SS Wake pulse: In LP Mode, a wake pulse may be used on the SS pin to either trigger an LPB acquire burst or to

wake the device in advance of communications. The pulse should be at least 22 µs in duration.

When used prior to communications, there should be a delay of 100 µs to 1 ms between the end of the SS Pulse and

the following SS assertion.

4.4.4 Sleep Mode

Sleep mode offers the lowest possible current drain, in the low microamp region.

Figure 4-3. LP Mode SPI Operation

SPI Operatio n with LPB = 0

SPI Operatio n with LPB = 1

Note: With LPB = 1, a pulse on SS with or without communications trig gers an acquisition burst

to follow communications. Pulse width > 22 µs.

Acquire Bursts

>22us

/SS from host

SCLK from Host

Host Data Output

(QT2100 Input - MOSI)

command bytes

response bytes

QT Data Output 3-state 3-state

(QT2100 Out - MISO)

don't care don't care

don't care don't caredon't care

don't care

No SPI Communication SPI Communication

Acquire Bursts

>22us

/SS from host

SCLK from Host

Host Data Output

(QT2100 Input - MOSI)

command bytes

response bytes

QT Data Output 3-state 3-state

(QT2100 Out - MISO)

don't caredon't care don't care

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Sleep mode is a special case of LP mode, where the sleep duration between bursts is infinite. All comments

concerning LP mode, including about SPI communications, apply equally to Sleep mode, except that the LPB bit is

ignored and bursts are always generated after an SPI transfer or SS wake pulse as if LPB = 1.

Note: In Sleep mode the QT2100 only performs acquisition bursts following being woken by SS. This has

two effects:

Touch detection only occurs following SS-wake pulses, and hence CHANGE can only go high at that time.

The QT2100 cannot drift its internal references unless the host sends periodic SS-wake pulses. If the host

does not do this, then it should command the QT2100 to recalibrate when it sets the QT2100 into a different

operating mode.

This mode can be used by the host to create its own LP Mode timings via the SS wakeup pulse method.

4.4.5 Sync Mode

This mode is useful for low frequency noise suppression, for example from mains frequencies in line-operated

appliances. Acquisition bursts are synchronized to the SS-wake pulses from the host.

Sync mode is very similar to LP Mode 4, with two differences:

It does not operate as in Free Run mode when a touch is first detected

The LPB bit is ignored and a burst is always generated after each SS wakeup or SPI transfer as if LPB = 1

Not operating as in Free Run mode when a touch is first detected (before DI confirmation has taken place) means

that acquisition bursts are restricted to the immediate time after a sync signal (SS), heightening the effect of low

frequency noise suppression.

In many applications of Sync mode the DI filter will need to be set to two counts, to avoid the QT2100 response time

being unacceptably lengthened as a consequence of this.

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5. SPI Commands

5.1 Introduction

Each communication exchange between the QT2100 and the host device consists of 3 bytes transmitted each way.

The host controls the clock signals and the timing of the exchange.

The data sent by the host indicates the command mode and the device settings where appropriate. There are four

command modes, selectable through bits 5 – 7 of the first byte (byte 0, Req bits):

Normal Exchange mode (Req = 000)

Custom Threshold command mode (Req = 100)

Send Signal command mode (Req = 001)

Device Version command mode (Req = 010)

The device settings sent by the host in its three command bytes becomes effective immediately after all three bytes

are received by the QT2100. The response to these three bytes is three data bytes containing key detection

information.

5.2 Normal Exchange Mode

5.2.1 Introduction

The Normal Exchange mode (Req = 000) is the normal mode for communication between the host and the device.

Data is sent every time an SPI communication occurs in Normal Exchange mode. If one of the other commands is

sent by the host, the corresponding response will be sent during the subsequent 3-byte exchange.

This Normal Exchange response forms the default (start-up) QT2100 data.

5.2.2 Host Data

In Normal Exchange mode (Req = 000) the host sends the 3-byte data in Table 5-1.

Table 5-1. Normal Exchange Mode – Host Comman d Bytes

Host

Byte

Bit

76543210

0Req = 000 PROX SLD AKS

1 0 MOD DI LPB LP Mode

2Resolution CalW CalK Cal Key Num

Note: Bits labelled 0 should not be altered

AT42QT2100 [DATASHEET]

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Byte 0

AKS – Three bits used to determine the AKS mode, as shown in Table 5-2 (see Section 4.3.4 on page 15

for further information).

SLD – Scrolling device type selection.

SLD = 0: Wheel mode (default)

SLD = 1: Linear slider mode

PROX – This setting is included to ensure compatibility with host drivers designed for the QT1106. Any key

may be optimized as a proximity sensor but key 7 should be used in any application where AKS is required,

as it can be excluded from AKS by selecting AKS mode 101.

Req – Set to 000 to indicate Normal Exchange mode.

Byte 1

LP Mode – After each measurement and processing cycle the device goes to sleep for a period, the

duration of which is set by the LP mode as per Table 5-3.

Table 5-2. AKS Mode

AKS Bits AKS Option

000 AKS disabled (default)

001 AKS global: All 7 keys + slider/wheel are in the same group

010 AKS group 1: all keys

AKS group 2: slider/wheel

011 AKS group 1: keys 1 – 4

AKS group 2: keys 5 – 7

AKS group 3: slider/wheel

100 AKS group 1: keys 1 – 4

AKS group 2: keys 5 – 7 + slider/wheel

101 AKS group 1: keys 1 – 6 + slider/wheel

AKS group 2: key 7

Table 5-3. Sleep/Low Power Modes

LP Mode Bit s Operating Mode

000 Free run – 0 ms sleep period in each cycle (default):

Acquisition and processing carried out continuo usly with no sleep . This

mode has the highest power consu mp tion, but the quickest response.

001 60 ms sleep period in each cycle

010 120 ms sleep period in each cycle

011 240 ms sleep period in each cycle

100 480 ms sleep period in each cycle

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LPB – Sets the LP mode following burst option. See Figure 4-2 on page 14.

LPB = 0: If the host communicates with the device, or there is an SS pulse during any LP mode (modes

001 to 100), there will be no following burst. The only bursts that will take place are those that occur as

naturally defined by the LP mode noted above.

LPB = 1: If the host communicates with the device, or there is an SS pulse during any LP mode (modes

001 to 100), there will be an additional burst following SS raising high (default).

In modes 101 (Sync) and 110 (Sleep), there will always be a burst following SS raising high, regardless of

the LPB Setting. See Table 5-3 for a description of the Mode settings.

DI - Set the Detect Integrator noise filter function.

DI = 0: Two detections required to confirm a touch (faster but less noise immune).

DI = 1: Six detections required to confirm a touch (slower but more noise immune; appropriate for most

applications) (default).

MOD (Recal Time) – Sets the Maximum On-duration for all keys and slider/wheel. Controls the time from

the start of a detection to automatic recalibration of all channels. See Table 5-4 for allowed MOD times.

Note: in Sleep mode, all device timing is dependent on the regularity of SPI communications. See Section

4.4.4 on page 17 for more information.

101 Sync mode:

The QT2100 performs an acquisition burst when triggered by a rising edge

on SS and ‘heartbeat’ bursts at the same interval as LP Mode 4

110

Sleep:

The QT2100 performs an acquisition and processing cycle on ly when

triggered by a rising edge on SS, whether a low pul se or a communication

exchange.

111 Reserved

Table 5-4. Maximum On-duration in Free Run Mode

MOD Bits Maximum On-duration

00 10 s (default)

01 20 s

10 60 s

11 Infinite MOD – timeout disabled

Table 5-3. Sleep/Low Power Modes (Continued)

LP Mode Bits Operating Mode

AT42QT2100 [DATASHEET]

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Byte 2

Cal Key Num – key to be recalibrated when CalK = 1 (see Table 5-5).

CalK – Recalibrates the key(s) specified by Cal Key Num.

CalK = 0: No recalibration (normal state of this bit).

CalK = 1: The device recalibrates key(s).

CalW – Recalibrates the slider/wheel.

CalW = 0: No recalibration (normal state of this bit).

CalW = 1: The device recalibrates the slider/wheel.

Set CalK/CalW only once when required, and set CalK/CalW = 0 thereafter. If the bit is constantly set to 1,

the device will keep recalibrating and will never detect a touch.

Note that the device recalibrates automatically on power-up, so that the use of Recal should rarely be

required. Any channel used as a proximity detector should be recalibrated soon after each proximity

detection, to ensure stability.

Resolution – the resolution of the slider/wheel reported position (see Table 5-6 and Figure 5-1).

Note: A resolution change will only become effective on the next touch.

Table 5-5. Key Recalibration

Cal Key Num Bits Key

000 Recalibrate all keys (excluding slider/wheel)

001 Recalibrate Key 1

010 Recalibrate Key 2

011 Recalibrate Key 3

100 Recalibrate Key 4

101 Recalibrate Key 5

110 Recalibrate Key 6

111 Recalibrate Key 7

Table 5-6. Resolution

Resolution Bits Resolution

000 Reserved

001 2 Bits: 4 positions (0 – 3)

010 3 Bits: 8 positions (0 – 7)

011 4 Bits: 16 positions (0 – 15)

100 5 Bits: 32 positions (0 – 31)

101 6 Bits: 64 positions (0 – 63)

110 7 Bits: 128 positions (0 – 127) (default)

111 8 Bits: 256 positions (0 – 255)

AT42QT2100 [DATASHEET]

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Figure 5-1. Slider and Wheel Resolution

5.2.3 QT2100 Data

The three return bytes contain the response to the previously sent command. Initially it is assumed that the

previously sent command was a Normal Exchange command. The return bytes for the Normal Exchange command

is shown in Table 5-7.

Byte 0

CTL: Custom Threshold Loaded: If CTL = 1, a custom slider/wheel threshold has been loaded from the

host. This is set as a result of a Custom Threshold command. Once the QT2100 has received a custom

threshold, this bit is set and stays set until reset.

PM: Proximity Mode: This setting is disabled as there is no proximity mode on the QT2100 because each

key can be configured as a proximity sensor. This setting has been left to ensure compatibility with the

QT1106.

LPS: LP/Sleep State: If LPS = 1, the device was in LP, Sync, or Sleep mode when the requesting

command was received. If LPS = 0, the device was in Free Run mode.

2 bits

12 4567

3 bits

12 45678910

11 12 13 14 15

4 bits

Note: the first and last slider positions

(shaded) have larger touch areas.

Slider M ode

SNSKA

SNSA3 SNSKA

SNSA1 SNSKA

SNSA2 SNSKA

SNSA3

SNSKA

SNSA3 SNSKA

SNSA1 SNSKA

SNSA2 SNSKA

SNSA3

SNSKA

SNSA3 SNSKA

SNSA1 SNSKA

SNSA2 SNSKA

SNSA3

2 bits

3 bits

0123

1314 15

4 bits

W heel M ode

SNSKA

SNSA1

SNSKA

SNSA2

SNSKA

SNSA3

SNSKA

SNSA1

SNSKA

SNSA2

SNSKA

SNSA3

SNSKA

SNSA1

SNSKA

SNSA2

SNSKA

SNSA3

Table 5-7. Normal Exchange Mode – Return Bytes

QT2100

Byte

Bit

76543210

0CW CK EW EK LPS PM 0CTL

1 W K7 K6 K5 K4 K3 K2 K1

2Position

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

EK: Key(s) in Error: If EK = 1, there is a sufficient decrease in capacitance of one or more normal key(s)

from the reference level. The affected key will be recalibrated if this condition is seen for more than 1.5

seconds.

EW: Slider/Wheel in Error: If EW = 1, there is a sufficient decrease in capacitance of the slider/wheel from

the reference level. The slider/wheel will be recalibrated if this condition is seen for six successive cycles.

CK: Key(s) in Calibration: If CK = 1, one or more key(s) are being calibrated.

CW: Slider/Wheel in Calibration: If CW = 1, the slider/wheel is being calibrated.

Byte 1

K1–K7: Contains the key states of each key. A 1 in a bit position means the key is confirmed as being

touched.

W: The state of the wheel/rotor. A 1 means the slider/wheel is confirmed as being touched.

Byte 2

Position: The position of touch on the slider/wheel. If the slider/wheel is not being touched, the position will

be the position of the last touch.

AT42QT2100 [DATASHEET]

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5.3 Custom Threshold

5.3.1 Introduction

The Custom Threshold command mode (Req = 100) is used to modify the detection threshold of the slider/wheel. It

only needs to be sent once, for the new value to take effect, and then the Normal Exchange mode resumes (see

Section 5.2 on page 19). The new value will be in use until the chip is reset or a new custom threshold is sent.

5.3.2 Host Data

In Custom Threshold command mode the host sends the 3-byte data in Table 5-8.

Byte 0

Req – Set to 100 to indicate Custom Threshold command mode.

Byte 1

T1: Custom threshold value of the slider/wheel. Higher numbers are less sensitive. Touch detection uses

this threshold combined with a hysteresis equal to 25% of the threshold (with a minimum hysteresis value of

one).

Power-up default setting: 30

Note: Custom Threshold Command is only used if the detection threshold of the slider/wheel needs to be

changed from the power-up default.

Byte 2

Always set to 0.

5.3.3 QT2100 Data

The QT2100 response to the Custom Threshold command is the Normal Exchange report.

Once the custom thresholds have been set, the CTL bit in the Normal Exchange report is set to 1 to indicate that the

changed threshold has been applied (see Table 5-7).

Table 5-8. Custom Threshold Comman d Mod e – Host Command Bytes

Host

Byte

Bit

76543210

0Req = 100 0 0 0 0 0

1T1 – Slider/Wheel Threshold

200000000

Note: Bits labelled 0 should not be altered

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5.4 Send Debug Data

5.4.1 Introduction

In a Send Debug Data exchange (Req = 001) the host requests the QT2100 to send 16-bit debug data on the next

3-byte exchange.

5.4.2 Host Data

In Send Debug Data command mode the host sends the 3-byte data in Table 5-9.

Byte 0

Debug Data: 1 bit, specifying the debug data that should be returned. Either of two 16-bit debug data states

may be requested:

Debug Data = 0: Reference – the reference level used by the QT2100 for comparison with the current

measurements to detect touch. The reference value is a 16-bit unsigned integer.

Debug Data = 1: Delta – the difference between the reference level and the current level, indicating how

close the channel is to detecting touch. The delta value is a 16-bit signed integer.

Req: Set to 001 to indicate Send Debug Data command mode.

Byte 1

Channel: 4 bits indicating the measurement channel for which the Send Debug Data is requested.

Channels are mapped to keys or slider/wheel electrodes, as in Table 5-10.

Table 5-9. Send Debug Data Command Mode – Host Command Bytes

Host

Byte

Bit

7 6 5 4 3 2 1 0

0Req = 001 0 0 0 0 Debug

Data

10000 Channel

200000000

Note: Bits labelled 0 should not be altered

Table 5-10. Channel Mappings

Channel Sensing Object

0Key B1

1Key B2

2Key B3

3Key B4

4Key B5

5Key B6

6Key B7

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Byte 2

Always set to 0.

5.4.3 QT2100 Data

During this exchange, the QT2100 returns the data requested on the previous exchange (Normal Data by default),

and at the next exchange the requested debug data is returned.

Byte 0

State of Channel: Indicates the current state of the channel.

Byte 1

LSB Delta/LSB Reference: The least significant 8 bits (LSB) of the Reference/Delta signal.

Byte 2

MSB Delta/MSB Reference: The most significant 8 bits (MSB) of the Reference/Delta signal.

7Slider/Wheel A1

8Slider/Wheel A2

9Slider/Wheel A3

Table 5-10. Channel Mappings (Continued)

Channel Sensing Object

Table 5-11. Send Debug Data Command Mode – Return Bytes

QT2100

Byte

Bit

76543210

0St ate of Channel

1LSB Delta/LSB Reference

2MSB Delta/MSB Reference

Table 5-12. Sensor States

State Code Sensor State

0x01 Calibration

0x02 No Detect (no touch)

0x04 Filter In (to confirm touch)

0x08 Detect (touched)

0x10 Filter out (to confirm release)

0x20 Recal (positive error recalibration)

0x40 Fault Check

AT42QT2100 [DATASHEET]

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5.5 Device Version

5.5.1 Introduction

In a Device Version exchange (Req = 010) the host requests the QT2100 to send the device ID and Firmware

version information.

5.5.2 Host Data

In Device Version command mode the host sends the 3-byte data in Table 5-13.

Byte 0

Req: Set to 010 to indicate Device Version command mode.

Byte 1

Always set to 0.

Byte 2

Always set to 0.

5.5.3 QT2100 Data

During this exchange, the QT2100 returns the data requested on the previous exchange (Normal Data by default),

and at the next exchange the requested data is returned.

Byte 0

Device ID: the device ID; always 108 (0x6C)

Byte 1

Version Major: 4 bits, indicating the major version of the device.

Version Minor: 4 bits, indicating the minor version of the device.

For example, firmware version 1.0 would be indicated as 0x10.

Table 5-13. Device Version Command Mode – Host Command Bytes

Host

Byte

Bit

7 6 5 4 3 2 1 0

0Req = 010 0 0 0 0 0

100000000

200000000

Note: Bits labelled 0 should not be altered

Table 5-14. Device Version Command Mode – Return Bytes

QT2100

Byte

Bit

7 6 5 4 3 2 1 0

0Device ID = 108 (0x6C)

1Version Major Ve rsion Minor

2Build

AT42QT2100 [DATASHEET]

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Byte 2

Build: The build of this firmware version.

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6. Specifications

6.1 Absolute Maximum Specifications

6.2 Recommended Operating Conditions

VDD –0.3 to +6.0 V

Max continuous pin current, any control or drive pin ±20 mA

Short circuit duration to ground or Vdd, any pin Infinite

Voltage forced onto any pin –0.3 V to (Vdd + 0.3) V

CAUTION: Stresses beyond those listed under Absolute Maximum Specifications may cause permanent damage to

the device. This is a stress rating only and functional operation of the device at these or other conditions beyond

those indicated in the operational sections of this specification is not impli ed. Exposure to absolute maximum

specification conditi ons for extended periods may affect device reliability

Operating temperature –40°C to +85°C

Storage temperature –50°C to +125°C

VDD +2.0 to 5.5 V

Short-term supply ripple + noise ±20 mV / s

Long-term supply stability ±100 mV

Cs range, keys 1 to 100 nF

Cs range, slider/wheel 4.7 to 220 nF

Cx range 0 to 50 pF

AT42QT2100 [DATASHEET]

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6.3 AC Sp ecifications

6.4 DC Sp ecifications

Vdd = 5.0V, Cs keys = 4.7 nF, Cs slider/wheel = 15 nF; circuit of Figure 1-1

Parameter Description Min Typ Max Units Notes

Tsu Start -up to SPI time –50 60 ms From cold start

Trc Recalibration time –300 –ms Depends on ground loading of

electrodes and Cs selection

Fc Burst center frequency –100

80 –kHz Spread spectrum disabled

Spread spectrum enabled

Fm Burst modulation, percent –15 – % Total deviation

Tpc Sample pulse duration –2.66

5.85 –µs Spread spectrum disabled

Spread spectrum enabled

Tbd Acquire burst duration –20

25 –ms Spread spectrum disabled

Spread spectrum enabled

(Total for all 3 acquire burst groups)

Tdf6 Response time – Free Run

mode, DI 6 samples –120 –ms Spread spectrum disabled

Tdf2 Response time – Free Run

mode, DI 2 samples –40 –ms Spread spectrum disabled

Tdl Response time – LP mode –280 –ms LP Mode 2, DI = six counts

Tdr Release time – all modes –40 –ms End of touch

Vdd = 5.0V, Cs keys = 4.7 nF, Cs slider/wheel = 15 nF; circuit of Figure 1-1

Parameter Description Min Typ Max Units Notes

Vil Low input logic level 0 – 0.3 × Vdd V

Vhl High input logic level 0.7 × Vdd –Vdd V

Vol Low output voltage – – 0.5 V7mA sink

Voh Hig h output voltage Vdd–0.5 – – bits 2.5 mA source

Iil Input leakage current – – ±1 µA

Ar Acquisition resolu tion –14 –bits

Trst External reset low pu lse width 2 – – µs

AT42QT2100 [DATASHEET]

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6.5 SPI Bus Specifications

Figure 6-1. Data Byte Exch an ge – Sign als

Parameter Specification

Data bits 8 data bits

Data transmission Shift out on falling edge

Shift in on rising edge

Three bytes per transmission, byte 1 most significant bit sent first

Clock idle Clock idle high

Maximum clock rate 750 kHz

Minimum time betw een exchanges 500 µs

SAMPLE

MOSI/MISO

CHANGE

MOSI PIN

CHANGE

MISO PIN

SCK

MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

Figure 6-2. Data Byte Exchange – Timings

6.6 External Reset

6.7 Internal Resonator

SS must be held

low between

bytes of an

exchange.

Period Min Max Unit General Min Max Unit

SS Low to SCK – Free-run mode 2 – µsRise/Fall Time –1600 ns

SS Low to SCK – LP mode 22 –µsSetup 10 –ns

S2 SCK to SS High 20 –µsHold 333 –ns

S3 SCK Low Pulse 666 –ns

S4 SCK High Pulse 666 –ns

S5 SCK Period S1 –ns

S6 Between Bytes –µs

S7 SS High to Tristate –20 ns

Parameter Description Operation

VRST Threshold voltage low (Activate)

Threshold voltage high (Release) 0.2 × Vdd

0.9 × Vdd

Parameter Operation

Internal RC oscillator 8 MHz with spread-spectrum modifier during measurement

bursts, if enabled

AT42QT2100 [DATASHEET]

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6.8 Signal Processing

6.9 Power Consumption

6.9.1 Spre ad Spectrum Disabled

Figure 6-3. Idd Curve

Vdd = 5.0V, Cs keys = 4.7 nF, Cs slider/wheel = 15 nF; circuit of Figure 1-1

Description Min Units Notes

Detection threshold (keys) 10 counts Threshold for increase in Cx load

Detection threshold (slider/wheel) 30 counts Changeable through SPI

Detection hyster esis (keys) 2counts

Detection hysteresis (slider/wheel) 5counts 25 percent of slider/wheel detectio n threshold

DI filter, start of touch, normal mode 6samples Must be consecutive or detection fails

DI filter, start of touch, fast DI mode 2samples Must be consecutive or detection fails

Table 6-1. Power Consumption (µA)

Vdd

LP Mode 2V 3.3 V 5V

0950 1940 4350

1190 420 1050

295 205 640

360 120 320

440 80 200

Sleep 15 18 22

Note: Power measurements taken 4.7 nF capacitors on the keys and 15 nF capacitors on the slider electrodes.

1000

2000

3000

4000

5000

01234

LP Mode

Current (uA)

Vdd = 2V Vdd = 3.3V Vdd = 5V

AT42QT2100 [DATASHEET]

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6.9.2 Spread Spectrum Enabled

Figure 6-4. Idd Curve

Table 6-2. Power Consumpt io n ( µA)

Vdd

LP Mode 2V 3.3 V 5V

0955 2050 4450

1210 510 1250

2105 260 760

365 150 390

440 95 235

Sleep 10 18 22

Note: Power measurements taken 4.7 nF capacitors on the keys and 15 nF capacitors on the slider electrodes.

1000

2000

3000

4000

5000

01234

LP Mode

Current (uA)

Vdd = 2V Vdd = 3.3V Vdd = 5V

AT42QT2100 [DATASHEET]

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6.10 Mechanical Dimensions

6.10.1 32-pin 5 x 5 mm MLF

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9554E–AT42–01/13

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9554E–AT42–01/13

6.11 Part Marking

6.11 .1 32-pin 5 x 5 mm MLF

Either part marking may be used. They are functionally identical.

Pin 1 ID

Date Code Description

W=Week code

Wweek code number 1-52 where:

A=1 B=2 .... Z=26

then using the underscore A=27...Z=52

Date Code

Abbreviated

part number

Code revision

1.1, Released

Please use this

marking to obscure

any reference to

ATtiny88 (or similar).

Atmel and lot

marking are

acceptable to remain

visible (Bar position

may be altered to

match existing

markings)

Pin 1 ID

Shortened

part number

Code revision

1.1, Released

LINE 4:

ATMEL LOTCODE

TRACEABILITY

(Variable field)

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

6.11.2 32-pin 7 x 7 mm TQFP

Either part marking may be used. They are functionally identical

Pin 1 ID

QT2100

Date Code

YWW= Date programmed

Date Code Description

WW week code number 1-52

Yyear code letter 1-26 where: A=2001...J=2010 ...Z=2026

AU 1R1

Shortened

Part Number

Code

Revision 1.1,

Release

Pin 1 ID

QT2100

AU 1R1

Shortened

Part Number

Code

Revision 1.1

Released

ATMEL

LOTCODE

Lot Number

(Variable Text)

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

6.12 Part Numbers

The part number comprises:

AT = Atmel

42 = Touch Business Unit

QT = Charge-transfer technology

2100= (2) Slider/Wheel (10) number of channels (0) variant number

AU = TQFP chip

MU = MLF chip

R = Tape and reel

6.13 Moisture Sensitivity Level (MSL)

Part Number Description

AT42QT2100-MU 32-pin 5 × 5 mm MLF RoHS compliant IC

AT42QT2100-MUR 32-pin 5 × 5 mm MLF RoHS compliant IC

AT42QT2100-AU 32-pin 7 × 7 mm TQFP RoHS compliant IC

AT42QT2100-AUR 32-pin 7 × 7 mm TQFP RoHS compliant IC

MSL Rating Peak Body Temperature Specifications

MSL3 260oCIPC/JEDEC J-STD-020

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

Appendix A. Migrating From QT1106 to QT2100

A.1 Introduction

The QT2100 is a replacement for the QT1106. As such, it is host-compatible with the QT1106 allowing existing

applications to be switched over without any changes to the host firmware.

Some changes to the application circuit will, however, be required and these are documented in this appendix.

A.2 Pin Configuration

The QT2100 has a different pin-out to the QT1106 (see Table A-1).

Table A-1. Pin Compatibility

Pin QT2100 Name QT1106 Compatibility

1SNSKB SNSB

2SNSB3

3SNSKB SNSB

4VDD QT1106 range is +2.8 V to +5.0 V

5VSS

6SNSKB SNSB

7SNSB4

8SNSB5

9SNSKB SNSB

10 SNSKB SNSB

11 SNSKB SNSB

12 SNSB6

13 SNSB7

14 SS

15 MOSI

16 MISO

17 SCK

18 VDD QT1106 range is +2.8 V to +5.0 V

19 DRDY Optional use on QT210 0

20 CHANGE

21 VSS

22 SPREAD External oscillator circuit not required for QT2100

23 SNSA1

24 SNSKA SNSA

25 SNSA2

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

A.3 Spread Spectrum Implementation

A SPREAD pin is provided which may be tied to Vdd or Ground via a resistor to enable/disable spread-spectrum

operation.

A.4 Component Retuning

In general it is expected that unchanged sense components will show little difference with the QT2100 for the same

sensor electrodes as the QT1106, but there may be cases where performance is improved by retuning component

values of Cs and Rs to the application circuit.

A.5 Components

An external oscillator is not required for QT2100.

A.6 Proximity

On the QT2100 any of the keys can be configured as proximity sensors but see Section 4.3.6 on page 15 for the

exception to this.

26 SNSKA SNSA

27 SNSA3

28 SNSKA SNSA

29 RESET

30 SNSB1

31 SNSKB SNSB

32 SNSB2

Table A-1. Pin Compatibility (Continued)

Pin QT2100 Name QT1106 Compatibility

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

Associated Documents

For additional information, refer to the following document (downloadable from the Touch Technology area of the

Atmel website, www.atmel.com):

QTAN0079 Buttons, Sliders and Wheels Sensor Design Guide

Atmel AVR3000: QTouch Conducted Immunity Application Note

QTAN0087 Proximity Design Guide

Revision History

Revision No. History

Revision AX – March 2011 Initial release for chip revision 0.6 – Preliminary

Revision BX – March 2011 Updated for chip revision 1.0

Revision CX – November 2011 Updated for chip revisi on 1.1 – Released

Revision D – November 2012 General update

Revision E – January 2013 Applied new template

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