AT42QT2120-XUR

Overview

The AT42QT2120-XUR is a QTouchADC capacitive touch sensor IC manufactured by Microchip Technology. It supports up to 12 keys in communications mode or 5 keys in standalone mode, with provisions for slider and wheel configurations. The device operates on a supply voltage range of 1.8 V to 5.5 V and features an I2C interface with a fixed slave address of 0x1C. It utilizes patented spread-spectrum technology for noise immunity and includes signal processing functions such as self-calibration, auto drift compensation, and Adjacent Key Suppression (AKS). The component is housed in a 20-pin TSSOP package.

Feature Summary

• Patented QTouchADC charge-transfer technology providing high noise immunity without external sampling capacitors.
• Integrated signal processing including self-calibration, auto drift compensation, and Adjacent Key Suppression (AKS) for reliable detection.
• Dual operational modes: Communications mode for configurable settings via I2C, and Standalone mode for fixed firmware operation.
• Supports various electrode designs including single solid, ring-shaped, spatially interpolated wheels, and resistorless sliders.

Applications

• Consumer electronics requiring multi-key touch interfaces
• Appliances utilizing slider or wheel controls
• Industrial panels requiring proximity sensing capabilities

Procurement Notes

Verify the specific ordering suffix against the manufacturer's current documentation to ensure correct packaging and tape-and-reel specifications. Confirm RoHS compliance status and moisture sensitivity level requirements prior to assembly planning. Ensure the host system supports the required I2C protocol if operating in communications mode.

Selection Notes

Select this component when a solution supporting up to 12 independent touch keys or combined slider/wheel inputs is required. Choose Communications mode for dynamic configuration of thresholds and suppression settings via I2C. Opt for Standalone mode if minimizing external microcontroller overhead is necessary, noting that settings are fixed at startup. Ensure the application panel thickness and electrode materials align with the specified design guidelines.

Part Context

The AT42QT2120 belongs to the QTouch family of capacitive touch sensor drivers from Microchip Technology. It is designed to replace mechanical switches in user interfaces, offering robust performance in electrically noisy environments. The device integrates all necessary signal processing, reducing the bill of materials by eliminating external capacitors typically required in other touch sensing architectures.

Replacement Considerations

Consult official Microchip documentation for qualified substitute part numbers within the same product family. Verify pin compatibility and software register mapping before implementing any cross-model replacements.

FAQ

How does the AT42QT2120 handle adjacent key presses?

The device incorporates patented Adjacent Key Suppression (AKS) technology, which allows tightly spaced keys to be used without loss of selectability. It ensures only one key in a defined AKS group is reported as touched at any given time.

What is the function of the CHANGE line in Communications Mode?

The CHANGE line is an active low open-drain output that signals the host when there is a change in the Detection Status or Key Status bytes. It helps minimize power consumption by allowing the device to remain in sleep mode until a touch event occurs.

Can the AT42QT2120 operate without an I2C connection?

Yes, in Standalone Mode, the device operates without an I2C interface. The Mode pin must be connected to Vdd before power-up. In this mode, key detection is reported via discrete output pins, and settings are fixed in firmware.