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NXP Semiconductors MMA6851BKWR2
- Part No.:
- MMA6851BKWR2
- Manufacturer:
- NXP Semiconductors
- Category:
- Accelerometers
- Package:
- 16-QFN Exposed Pad
- Datasheet:
-
MMA6851BKWR2.pdf
- Description:
- ACCELEROMETER 25G SPI 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,076
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Product details
Overview
MMA6851BKWR2 from NXP Semiconductors (formerly Freescale) is a single-axis, ±25g, SPI-output inertial sensor designed for automotive airbag deployment systems. It features 10-bit digital output, programmable arming logic, 12 selectable low-pass filter configurations (50–1000 Hz), and AEC-Q100 Grade 1 qualification for under-hood operation.
For engineers reviewing the MMA6851BKWR2 datasheet, MMA6851BKWR2 pinout, MMA6851BKWR2 application, or MMA6851BKWR2 equivalent, this page delivers verified technical context, exact pin functions, automotive-grade timing behavior, offset cancellation performance, and validated alternative options for airbag control unit design.
Technical Context
The MMA6851BKWR2 integrates an over-damped lateral MEMS g-cell with a sigma-delta ADC, SINC-based digital filtering, and configurable IIR low-pass filters. Its internal 8 MHz oscillator feeds a programmable clock divider to support 50–1000 Hz cutoff frequencies across 12 discrete LPF settings.
It implements dual-regulator architecture: VREG (2.5 V ±0.08 V) powers digital circuitry, while VREGA (2.5 V ±0.08 V) supplies analog blocks. The ARM/PCM pin supports three arming modes-moving average, count, or unfiltered-with open-drain configuration and user-selectable polarity via DEVCFG register bits A_CFG[2:0].
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Full-Scale Range | ±25 g - calibrated range optimized for crash pulse detection in frontal airbag systems |
| Digital Output Resolution | 10-bit signed or unsigned SPI output - provides 20.479 LSB/g sensitivity for precise acceleration quantization |
| Low-Pass Filter Options | 12 selectable configurations (50 Hz to 1000 Hz, 3- or 4-pole) - enables tuning for noise rejection vs. response time in real-time crash discrimination |
| Offset Cancellation | 6.29 s averaging period with < 0.25 LSB/s slew rate - ensures stable zero-g baseline under thermal drift and long-term bias drift |
| Supply Voltage | 3.3 V or 5.0 V single supply - compatible with legacy automotive MCU power domains without level-shifting |
| AEC-Q100 Qualification | Grade 1 (−40 °C to +105 °C ambient) - validated for engine compartment and passenger cabin mounting locations |
| Power Consumption | 3.0–7.0 mA typical - supports low-duty-cycle wake-up architectures in battery-sensitive airbag controllers |
Pinout & Package
Pb-free 16-pin QFN package, 6 mm × 6 mm, exposed thermal pad (Case 2086-01). Pin 17 (PAD) internally connected to VSS.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VREGA | Analog supply input | 2.5 V regulated supply for analog front-end; requires 1 μF ceramic capacitor to VSSA |
| VSS / VSSA | Digital and analog ground | Separate return paths prevent noise coupling between digital switching and analog sensing circuits |
| VREG | Digital supply input | 2.5 V regulated supply for digital logic and SPI interface; requires 1 μF capacitor to VSS |
| VCC | Main supply input | 3.3 V or 5.0 V primary power rail; internal regulators derive VREG/VREGA; requires 0.1 μF decoupling |
| ARM/PCM | Configurable output | Open-drain arming signal or PCM output; polarity and mode set via DEVCFG register A_CFG[2:0] |
| CS, SCLK, MOSI, MISO | SPI interface | Standard 4-wire SPI with internal pullup on CS and pulldowns on SCLK/MOSI; supports up to 10 MHz clock |
| TEST/VPP | Factory programming | Must be tied to VSS in application; not used during normal operation |
Key Features
| Feature | Design Value |
|---|---|
| Programmable arming logic | Three modes (moving average, count, unfiltered) with user-configurable thresholds - enables flexible crash decision algorithms without external logic |
| On-chip offset monitoring | Detects >±0.125 LSB offset drift and asserts fault flag - provides built-in diagnostic coverage for ISO 26262 ASIL-B compliance |
| Self-test capability | Two-level electrostatic deflection (ΔSTLow = 10.68–18.75 g, ΔSTHI = 21.37–39.38 g) - allows full functional verification at power-on or runtime |
| Robust supply monitoring | Independent undervoltage/overvoltage detection on VCC, VREG, and VREGA with hysteresis - prevents erroneous outputs during brown-out conditions |
| High shock survivability | ±2000 g unpowered shock rating - withstands mechanical stress during vehicle assembly and service handling |
Applications
| Frontal Crash Detection | Side-Impact Sensing |
|---|---|
|
Use Scenario: Mounted on vehicle firewall to detect rapid deceleration during head-on collisions. IC Role / Device Role / Timing Role: Primary acceleration transducer feeding airbag control unit (ACU) with real-time 10-bit SPI data at ≤1000 Hz bandwidth. Use Value: ±25 g range and 400 Hz 4-pole LPF option provide optimal signal-to-noise ratio for distinguishing crash pulses from road noise. |
Use Scenario: Integrated into door module to sense lateral acceleration during side collisions. IC Role / Device Role / Timing Role: Single-axis X-direction sensor providing acceleration magnitude to side airbag ECU for deployment timing. Use Value: Over-damped g-cell (ζ = 2.46–9.36) eliminates resonance artifacts at 10.8–15.9 kHz, ensuring clean transient response. |
| Occupant Position Sensing | Pre-Crash System Input |
|
Use Scenario: Mounted near seat track to monitor occupant proximity and posture before impact. IC Role / Device Role / Timing Role: Low-power inertial monitor enabling occupancy classification via sustained acceleration patterns. Use Value: 3.0–7.0 mA supply current and programmable arming enable duty-cycled wake-up for extended battery life. |
Use Scenario: Used in predictive collision avoidance systems to trigger pre-tensioner activation milliseconds before impact. IC Role / Device Role / Timing Role: Fast-response sensor with <6.6 μs unfiltered arming assertion time feeding early-warning logic. Use Value: Unfiltered mode latency of 5.00–6.579 μs allows sub-millisecond reaction for seatbelt pre-tensioning. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar inertial sensing applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ADXL312WBRMZ-RL | 2-axis, ±18 g, I²C interface, 13-bit resolution, no integrated arming logic | Lacks dedicated arming output and AEC-Q100 Grade 1 qualification; requires external comparator for crash decision | Preferred for non-safety-critical motion sensing where SPI interface and ASIL-ready arming are not required |
| MMA8451Q | 3-axis, ±2/4/8 g, I²C/SPI, embedded FIFO, motion detection engine, AEC-Q100 Grade 2 | Lower max range (±8 g), wider temp range (−40 °C to +105 °C), but lacks programmable arming and offset monitor diagnostics | Suitable for rollover or pedestrian protection systems where multi-axis data and lower g-range suffice |
Compared with ADXL312WBRMZ-RL and MMA8451Q, the MMA6851BKWR2 uniquely combines single-axis ±25 g range, AEC-Q100 Grade 1 qualification, hardware arming output, and on-chip offset monitoring-making it purpose-built for ASIL-B-compliant frontal airbag deployment.
Availability
MMA6851BKWR2 is available at Aetrix Electronics and suitable for automotive airbag control units, occupant detection modules, and pre-crash system designs requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for MMA6851BKWR2 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 acquired Freescale in 2015 and continues its automotive sensor portfolio with rigorous AEC-Q100 validation and functional safety support.
The MMA685x family was engineered specifically for automotive safety-critical applications, emphasizing robustness, deterministic timing, and integrated diagnostics for airbag and restraint control systems.
FAQ
What is the full-scale range and sensitivity of the MMA6851BKWR2?
The MMA6851BKWR2 has a fixed ±25 g full-scale range. Its digital sensitivity is 20.479 LSB/g for 10-bit unsigned output, corresponding to a nominal zero-g code of 512. This value is factory-trimmed and specified across −40 °C to +105 °C ambient temperature per the datasheet's Table 59.
Does the MMA6851BKWR2 support both signed and unsigned SPI output formats?
Yes, the MMA6851BKWR2 supports both formats. The SD bit in the DEVCFG register (address $0B, bit 3) selects output format: SD = 1 enables unsigned output (zero-g = 512), while SD = 0 enables signed output (zero-g = 0). This setting is configurable during initialization before ENDINIT is asserted.
How is the ARM/PCM pin configured for arming output in the MMA6851BKWR2?
The ARM/PCM pin is configured via A_CFG[2:0] bits in the DEVCFG register (address $0B). For example, A_CFG = 010 selects moving average mode with active-high output and pulldown current. Configuration occurs during initialization and is locked after ENDINIT is set. Unused ARM pins must remain unconnected.
What low-pass filter options are available on the MMA6851BKWR2, and how are they selected?
The MMA6851BKWR2 offers 12 low-pass filter options: six at 64/fOSC (cutoffs 100–1000 Hz) and six at 128/fOSC (cutoffs 50–500 Hz), all 3- or 4-pole. Selection is done via LPF[3:0] bits in the DEVCFG_X register (address $0C). Filter choice directly impacts latency and noise rejection-e.g., 400 Hz 4-pole provides 380–420 Hz cutoff with minimal phase distortion.
Is the MMA6851BKWR2 qualified to AEC-Q100, and what grade does it meet?
Yes, the MMA6851BKWR2 is qualified to AEC-Q100 Revision G, meeting Grade 1 requirements (−40 °C to +105 °C operating ambient temperature). This qualification covers device-level stress testing including HTOL, TCT, ESD, and mechanical shock, confirming suitability for under-hood and passenger compartment automotive safety systems.
MMA6851BKWR2 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- 16-QFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Digital
- Axis:
- X
- Acceleration Range:
- ±25g
- Sensitivity (LSB/g):
- 20.48
- Sensitivity (mV/g):
- -
- Bandwidth:
- -
- Output Type:
- SPI
- Voltage - Supply:
- 3.135V ~ 5.25V
- Features:
- -
- Operating Temperature:
- -
- Grade:
- Automotive
- Qualification:
- AEC-Q100
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN-EP (6x6)
MMA6851BKWR2 FAQ
1.How can I place an order for MMA6851BKWR2 through Aetrix?
Please submit a Request for Quotation (RFQ) for MMA6851BKWR2 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MMA6851BKWR2 reliable?
The price and inventory of MMA6851BKWR2 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMA6851BKWR2 is usually 5 days.
3.What payment methods are accepted for MMA6851BKWR2?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMA6851BKWR2 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MMA6851BKWR2?
MMA6851BKWR2 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MMA6851BKWR2 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MMA6851BKWR2?
For technical support, including MMA6851BKWR2 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMA6851BKWR2 requirements.
6.How does Aetrix verify that MMA6851BKWR2 is sourced from the original manufacturer or authorized distributors?
All MMA6851BKWR2 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MMA6851BKWR2 meets industry standards.
7.What is the process for return or replacement of MMA6851BKWR2?
All MMA6851BKWR2 units undergo pre-shipment inspection (PSI). If there is an issue with MMA6851BKWR2, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MMA6851BKWR2 part is unused and in its original packaging.
Return procedure for MMA6851BKWR2:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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