Microchip Technology AT42QT2100-MUR

Overview

AT42QT2100-MUR from Microchip Technology (formerly Atmel) is a QTouch® capacitive touch sensor IC supporting up to 7 discrete keys plus one slider or rotary wheel, operating via patented spread-spectrum charge-transfer technology. It delivers robust proximity and touch detection through glass up to 10 mm or plastic up to 15 mm, with SPI interface, adjustable sensitivity per channel via external Cs capacitors, and integrated drift compensation for stable operation in varying environmental conditions.

For engineers reviewing the AT42QT2100-MUR datasheet, AT42QT2100-MUR pinout, AT42QT2100-MUR application, or AT42QT2100-MUR equivalent, key selection considerations include burst-mode timing alignment, AKS group configuration for multi-key suppression, Cs capacitor tuning for electrode-specific sensitivity, and SPREAD pin control for noise-immune operation in EMI-prone environments.

Technical Context

The AT42QT2100-MUR acquires touch data in three sequential bursts: Burst 1 (B1–B3), Burst 2 (B4–B7), and Burst 3 (A1–A3), with DRDY held low during acquisition and high for 500 µs between bursts to enable synchronized SPI transfers. Each burst group supports independent sensitivity tuning via discrete Cs capacitors (CsB1–CsB7 for keys; CsA1–CsA3 for slider/wheel).

It implements patented Adjacent Key Suppression (AKS®) to prevent false multi-key activation, autodrift compensation that limits reference drift to ≤1 count/3 s toward touch and ≤1 count/0.5 s away, and Detect Integrator (DI) filtering requiring either 2 or 6 consecutive qualifying measurements before reporting touch or release - all executed without external oscillator or firmware intervention.

Key Specifications

Pinout & Package

AT42QT2100-MUR is housed in a 32-pin 5 × 5 mm MLF (Micro Lead Frame) RoHS-compliant package with exposed thermal pad connected to VSS. The central ground pad must be soldered directly to PCB ground plane; no signal traces permitted underneath the die area.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar capacitive touch sensor applications.

Compared with AT42QT2100-MUR, AT42QT1070-MAHR offers reduced footprint and BOM cost for pure key applications, while CY8CMBR2016-LQXI provides higher channel density and mutual-capacitance immunity at the expense of design complexity and toolchain dependency.

Availability

AT42QT2100-MUR is available at Aetrix Electronics and suitable for home appliance control panels, industrial HMI interfaces, PC peripheral scroll wheels, and medical device proximity wake systems requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant MLF packaging.

Supply support for AT42QT2100-MUR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology acquired Atmel in 2016 and maintains its QTouch® portfolio for robust, low-power capacitive sensing solutions targeting cost-sensitive consumer and industrial markets.

The AT42QT2100 product line was designed specifically for single-chip implementation of sealed, dielectric-overlaid touch interfaces - emphasizing ease of layout, minimal external components, and field-proven noise immunity in real-world EMI environments.

FAQ

What is the maximum panel thickness supported by AT42QT2100-MUR for key and slider/wheel operation?

The AT42QT2100-MUR supports up to 15 mm of glass or 10 mm of plastic for discrete key sensing, and up to 4 mm of glass or 3 mm of plastic for slider/wheel operation. These limits assume standard electrode sizing and Cs capacitor selection; thicker overlays require larger Cs values and may reduce signal-to-noise ratio. Performance validation is recommended for each mechanical stack-up using the QT2100 evaluation kit and Atmel Studio QTouch Library.

How does the AT42QT2100-MUR handle adjacent key interference during multi-finger touch?

The AT42QT2100-MUR implements patented Adjacent Key Suppression (AKS®) to suppress weaker signals within predefined key groups, allowing only the dominant touch to register. When AKS is enabled globally, only one key or the slider/wheel reports activation at a time. Group assignments are configurable via SPI; for example, setting AKS bits to 101 reserves Key B7 exclusively for proximity while permitting full multi-key operation elsewhere.

Can AT42QT2100-MUR operate without an external voltage regulator?

Yes, AT42QT2100-MUR operates directly from 2.0 V to 5.5 V and tolerates slow supply fluctuations via internal drift compensation. However, rapid voltage shifts (e.g., from digital switching noise) may cause false detections; in such cases, a local 0.1 µF bypass capacitor between VDD and VSS is mandatory, and a dedicated LDO is recommended if shared rail noise exceeds ±50 mV peak-to-peak.

What is the role of the SPREAD pin on AT42QT2100-MUR, and how should it be configured?

The SPREAD pin on AT42QT2100-MUR enables or disables spread-spectrum burst modulation: connect to VDD (via pull-up) to activate for superior noise immunity and reduced RF emissions, or to VSS (via pull-down) to disable for deterministic timing in synchronized systems. Leaving SPREAD floating is not allowed; incorrect biasing causes undefined burst behavior and potential SPI communication failure.

How does AT42QT2100-MUR manage recalibration after prolonged touch or environmental drift?

AT42QT2100-MUR performs automatic recalibration using two mechanisms: Maximum On Duration (MOD) timeout (configurable to 10/20/60 s or infinite) resets reference after sustained touch, and signal-error recalibration triggers individually on any channel showing ≥1.5 s of capacitance decrease - ensuring keys never lock "on" due to foreign objects or contamination. Both processes occur autonomously without host intervention.