NXP Semiconductors MMA8491QR1

Overview

MMA8491QR1 from NXP Semiconductors is a 3-axis multifunction digital accelerometer in a 12-pin QFN package, operating at 1.95–3.6 V. It functions either as a 45° tilt sensor with push-pull Xout/Yout/Zout outputs or as a 14-bit ±8 g I²C digital accelerometer with 1 mg/LSB resolution and <400 nA/Hz current consumption. It enables tamper detection in smart grid meters and tilt-based anti-theft triggers.

For engineers reviewing the MMA8491QR1 datasheet, MMA8491QR1 pinout, MMA8491QR1 application, or MMA8491QR1 equivalent, this page delivers verified functional modes (tilt detection vs. I²C read), exact threshold behavior (0.688 g / 43.5°), power sequencing (EN-controlled one-shot acquisition), output drive capability (7.3 mA source / 8.9 mA sink), and validated register map (0x00–0x06) - all confirmed from NXP Rev. 2.1 datasheet.

Technical Context

The MMA8491QR1 implements dual-mode operation: EN-triggered single-sample acquisition followed by STANDBY mode for data validity, with automatic zero-g offset compensation and internal 0.688 g threshold comparison per axis. Its 14-bit ADC output is accessible via I²C Fast Mode (400 kHz) using fixed 7-bit slave address 0x55.

It features two independent output subsystems: push-pull digital tilt outputs (Xout/Yout/Zout) with defined logic levels (VOH ≥ 0.85×VDD, VOL ≤ 0.15×VDD) and an I²C interface with open-drain SDA/SCL requiring external pull-ups. Power states are strictly controlled by EN and VDD - no internal oscillator or autonomous sampling.

Key Specifications

Pinout & Package

Package: 12-pin QFN, 3 mm × 3 mm, 0.65 mm pitch, with two NC pins and dual GND pins for noise immunity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar tilt-sensing and low-power accelerometer applications.

Compared with KX122-1037 and ADXL362, the MMA8491QR1 uniquely delivers hardware-accelerated 45° tilt decisions via three dedicated push-pull outputs - reducing MCU load, eliminating calibration code, and enabling faster system response than software-based alternatives.

Availability

MMA8491QR1 is available at Aetrix Electronics and suitable for smart grid tamper detection, white goods tilt sensing, and anti-theft motion trigger applications requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for MMA8491QR1 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT markets.

The MMA8491QR1 belongs to NXP's legacy MEMS accelerometer family designed specifically for cost-sensitive, ultra-low-power tilt and motion event detection - prioritizing hardware-based decision logic over programmability.

FAQ

What is the function of the EN pin on the MMA8491QR1?

The EN pin controls the MMA8491QR1's acquisition cycle: pulling EN HIGH initiates a single-sample acquisition across all three axes, followed by STANDBY mode where outputs are valid. Holding EN LOW places the device in SHUTDOWN mode (<68 nA). The MMA8491QR1 requires EN to exceed 1.95 V before sampling begins, and its 720 μs turn-on time defines the earliest point at which Xout/Yout/Zout or I²C data become reliable. This behavior is explicitly defined in Section 12.1 of the MMA8491QR1 datasheet.

Does the MMA8491QR1 support continuous measurement mode?

No, the MMA8491QR1 does not support continuous measurement. It operates exclusively in one-shot mode triggered by the EN pin - each HIGH pulse acquires exactly one sample per axis, then enters STANDBY mode until EN is pulsed again or the device powers down. There is no internal oscillator or autonomous sampling engine. This is confirmed in Figure 7 (Operating Modes) and Table 10, where only ACTIVE (one-shot) and STANDBY (data-hold) modes are defined - no "continuous" or "streaming" mode exists for the MMA8491QR1.

How do the Xout, Yout, and Zout pins behave during tilt detection?

Xout, Yout, and Zout are push-pull outputs that assert HIGH when the absolute acceleration on their respective axis exceeds 0.688 g (corresponding to >43.5° tilt from horizontal), and LOW when acceleration is ≤0.688 g. Each pin sources ≥7.3 mA and sinks ≥8.9 mA, allowing direct drive of LEDs, optocouplers, or MCU GPIOs without external components. Their state remains latched in STANDBY mode until the next EN pulse - a behavior verified in Sections 12.5 and Table 2 of the MMA8491QR1 datasheet.

What is the I²C slave address of the MMA8491QR1?

The MMA8491QR1 uses a fixed 7-bit I²C slave address of 0x55 (binary 01010101), as documented in Table 9 and Section 11.1.1 of the official datasheet. This address is hard-coded and not configurable. When performing a write transaction, the full 8-bit value is 0xAA (0x55 << 1 | 0); for read, it is 0xAB (0x55 << 1 | 1). The SDA and SCL lines are open-drain and require external pull-up resistors to VDD, consistent with standard I²C Fast Mode operation.

Can the MMA8491QR1 measure acceleration values below ±8 g?

No - the MMA8491QR1 has a fixed full-scale range of ±8 g, with 14-bit output resolution yielding 1 mg/LSB sensitivity across that entire range. It does not support range scaling, auto-ranging, or software-configurable gain. Values outside ±8 g saturate (e.g., +8.000 g = 0x1FFF, –8.000 g = 0xE000), and the device contains no internal mechanism to extend or compress the measurement span. This is specified in Section 2 (Features and benefits) and Table 5 (Mechanical characteristics) of the MMA8491QR1 datasheet.