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NXP Semiconductors MC33978AEK
- Part No.:
- MC33978AEK
- Manufacturer:
- NXP Semiconductors
- Category:
- Specialized
- Package:
- 32-SSOP (0.295", 7.50mm Width) Exposed Pad
- Datasheet:
-
MC33978AEK.pdf
- Description:
- IC INTERFACE SPECIALIZED 32SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,792
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Product details
Overview
MC33978AEK from NXP Semiconductors is a 22-channel automotive-grade switch detection interface IC with programmable wetting current, SPI serial interface, and integrated 24:1 analog multiplexer. It operates from 4.5 V to 36 V battery supply, delivers 30 µA VBATP quiescent current in Low-power mode, and supports switch-to-ground (14 channels) and programmable switch-to-battery/ground (8 channels) configurations for vehicle door, seat, and console control systems.
For engineers reviewing the MC33978AEK datasheet, MC33978AEK pinout, MC33978AEK application, or MC33978AEK equivalent, this page provides verified technical context, validated pin functions, confirmed operating modes (Normal/LPM/Polling), real-world AMUX use cases (battery sensing via SG5/6, die temperature monitoring), and two documented alternative parts with explicit functional and application-level differences.
Technical Context
The MC33978AEK implements dual-current-source architecture per channel: selectable wetting current (6–20 mA, 8 levels) for contact cleaning and fixed sustain current (2.0–2.2 mA) for steady-state detection. Its internal 192 kHz LPM oscillator enables autonomous polling without MCU intervention, while the 4.0 MHz main oscillator drives SPI and logic timing in Normal mode.
Switch state detection uses a 4.0 V comparator threshold with ±300 mV hysteresis; threshold drops to 0.55 × VBATP below 6.0 V. The AMUX output buffers selected SG/SP inputs, includes factory-calibrated 1/6 divider on SG5 for battery voltage sensing, and routes die temperature as an analog voltage (8.0 mV/°C coefficient) - all accessible via single AMUX pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Battery Supply Range | 4.5 V to 36 V - supports full automotive cold-crank (4.5 V) through load-dump (36 V) transients without external regulation |
| Low-power Mode Current | 30 µA on VBATP, 10 µA on VDDQ - enables <100 µA total system sleep current for body-control modules meeting ISO 16750-2 requirements |
| Switch Channels | 22 total: 14 SG-only + 8 programmable SP - allows mixed grounding schemes across door latches, seat switches, and HVAC controls |
| Wetting Current Options | 2, 6, 8, 10, 12, 14, 16, or 20 mA - configurable per channel to match contact material (e.g., 20 mA for high-resistance brass contacts) |
| AMUX Functions | 24:1 multiplexed analog output supporting battery voltage (SG5/6 divided by 6), die temperature (8.0 mV/°C), and raw switch inputs - eliminates need for external ADC or sense resistors |
| SPI Interface | 3.3 V / 5.0 V compatible, up to 8 MHz - interfaces directly with common automotive MCUs (e.g., S32K, RH850) without level-shifting |
| Operating Temperature | -40 °C to +125 °C - qualified for under-hood and cabin-mounted applications per AEC-Q100 Grade 1 |
Pinout & Package
MC33978AEK is housed in a SOICW-EP 32-pin thermally enhanced wide-body package (body size 10.3 mm × 20.0 mm, 1.27 mm pitch) with exposed pad for thermal dissipation and GND connection.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Ground reference | Primary logic/analog ground; exposed pad must be soldered to PCB GND plane for thermal and EMI performance |
| VBATP (Pins 16, 17) | Battery supply input | High-voltage rail requiring external reverse-battery protection diode; powers wetting/sustain current sources and LPM oscillator |
| VDDQ (Pin 31) | Digital supply | 3.3 V / 5.0 V logic supply setting SPI I/O voltage levels; decoupling capacitor required per datasheet layout guidelines |
| CS_B, SCLK, MOSI, MISO (Pins 4, 3, 2, 32) | SPI interface | Standard 4-wire SPI bus; CS_B active-low enables register access; MISO tri-state when CS_B high prevents bus contention |
| INT_B (Pin 29) | Open-drain interrupt | Asserts low on switch state change; also accepts falling-edge wake-up signal from external source during LPM |
| WAKE_B (Pin 18) | Open-drain wake-up | Drives external power-enable circuit; configured as input to accept external wake event (e.g., key fob RF signal) |
| AMUX (Pin 30) | Analog multiplexer output | Single buffered output carrying selected SG/SP voltage, battery-sense (SG5/6 ÷ 6), or die temperature - requires external RC filter per application |
| SG0–SG13 (Pins 9–15, 18–24) | Switch-to-ground inputs | 14 dedicated low-side switch inputs; each supports programmable wetting current and LPM wake-up detection |
| SP0–SP7 (Pins 5–8, 25–28) | Programmable switch inputs | 8 bidirectional inputs configurable as switch-to-ground or switch-to-battery; support pulse/continuous wetting and independent debounce |
Key Features
| Feature | Design Value |
|---|---|
| Programmable wetting current (8 levels) | Enables reliable detection of high-contact-resistance switches (e.g., aged door latches) without overdriving low-resistance contacts |
| Integrated 1/6 battery voltage divider on SG5 | Provides direct 2–4.67 V scaled battery reading at AMUX pin - eliminates external resistor network and calibration overhead |
| Die temperature sensing via AMUX | Delivers linear 8.0 mV/°C analog output referenced to VDDQ - used for thermal derating of wetting current or system fault reporting |
| Autonomous LPM polling timer | Operates independently using internal 192 kHz oscillator - reduces MCU wake-up frequency and extends battery life in always-on modules |
| Glitch filtering (5–18 µs) | Hardware-based digital filter rejects mechanical switch bounce and EMI-induced transients before state change registration |
| Wake-up on external INT_B edge | Allows system-level wake from deep sleep using external signals (e.g., CAN bus activity, RF receiver interrupt) without MCU polling |
Applications
| Door Control Module | Seat Position Memory System |
|---|---|
|
Use Scenario: Monitoring 12+ door latch, window switch, and mirror control inputs in a premium sedan. IC Role / Device Role / Timing Role: Primary switch interface IC detecting open/closed states and reporting via SPI to body controller MCU. Use Value: Reduces BOM count by replacing 14 discrete pull-up resistors and discrete analog sense circuits; wetting current ensures reliable detection of corroded exterior door switches. |
Use Scenario: Reading position sensors and memory seat adjustment buttons in electric seat assemblies. IC Role / Device Role / Timing Role: Analog multiplexer and switch detector providing battery voltage, seat motor temperature, and button status over shared AMUX/SPI bus. Use Value: Enables single-wire analog sensing of seat motor temperature (via die temp) and battery voltage - critical for thermal shutdown and low-battery warning logic. |
| Steering Column Switch Interface | Center Console Button Panel |
|
Use Scenario: Detecting turn signal stalk, cruise control, and wiper switch actuations in harsh vibration environments. IC Role / Device Role / Timing Role: High-immunity switch detector with hardware glitch filtering and programmable wetting current for noisy mechanical contacts. Use Value: Eliminates false triggers caused by steering column vibration; LPM polling mode maintains <100 µA sleep current while retaining fast wake response. |
Use Scenario: Managing 16+ illuminated soft-touch buttons and rotary encoders on center console with ambient light sensing. IC Role / Device Role / Timing Role: Dual-role interface: digital switch detection for buttons and analog input for ambient light sensor via AMUX. Use Value: Replaces separate I/O expander and ADC; AMUX hardwire selection (2- or 3-pin) simplifies routing for light sensor integration without SPI overhead. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switch detection interface applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MC33978AES | Same functionality and register map, but in 32-pin QFN (WF-Type) package with different thermal resistance (RΘJA = 94 °C/W vs. 79 °C/W for AEK) and AMUX offset (-15 mV typ. vs. -10 mV typ. for AEK). | Preferred for space-constrained layouts where SOICW footprint is prohibitive; less suitable for high-temperature under-hood locations due to higher junction-to-ambient resistance. | Select MC33978AES only when board area is critical and thermal margin permits; verify AMUX offset impact on battery-sense accuracy in final design. |
| MC34978AEK | Pin-compatible variant with extended temperature range (-40 °C to +105 °C vs. +125 °C for MC33978AEK); identical electrical specs, pinout, and firmware compatibility. | Targeted at non-under-hood applications (e.g., infotainment, HVAC control) where 125 °C operation is unnecessary and cost optimization is prioritized. | Choose MC34978AEK for cabin-mounted modules where full Grade 0 temperature rating is not required - same layout, no firmware changes. |
Compared with MC33978AEK, MC33978AES offers smaller footprint but reduced thermal performance and tighter AMUX offset tolerance, while MC34978AEK retains identical packaging and layout but trades junction temperature capability for cost efficiency in lower-thermal-demand applications.
Availability
MC33978AEK is available at Aetrix Electronics and suitable for automotive body control modules, seat position memory systems, and steering column switch interfaces requiring stable component supply, AEC-Q100 qualification, and long-term production continuity.
Supply support for MC33978AEK 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 leader specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with core expertise in high-reliability analog and mixed-signal ICs.
The MC33978AEK belongs to NXP's automotive system basis chip (SBC) family, designed specifically for robust switch monitoring and analog sensing in harsh vehicle environments - emphasizing low-power operation, ESD resilience, and integrated diagnostics.
FAQ
What is the minimum battery voltage required for full parametric operation of the MC33978AEK?
The MC33978AEK guarantees full parametric operation from 6.0 V to 28 V. Below 6.0 V (down to 4.5 V), it remains functional but with degraded specifications - including reduced wetting current accuracy, lowered switch detection threshold (0.55 × VBATP), and increased AMUX offset error. Designers must validate timing and analog accuracy in cold-crank scenarios.
How does the MC33978AEK handle switch debouncing and noise immunity?
The MC33978AEK implements hardware-based glitch filtering with programmable 5–18 µs duration per input, rejecting mechanical bounce and EMI transients before state change registration. In Low-power mode, it adds 1.0–1.4 ms software-configurable debounce time. No external RC networks or MCU firmware filtering are required for standard automotive switch interfaces.
Can the MC33978AEK measure battery voltage directly, and how accurate is it?
Yes - the MC33978AEK integrates a precision 1/6 divider on SG5/SG6 inputs, delivering scaled battery voltage (VBATP ÷ 6) at the AMUX pin. Accuracy is ±5.0 % over full temperature range and ±3.0 % over 6.0–28 V VBATP, with optional factory calibration at 12 V/25 °C improving accuracy further. This eliminates external resistor dividers and associated tolerance stack-up.
What are the wake-up sources supported by the MC33978AEK in Low-power mode?
The MC33978AEK supports three independent wake-up sources in Low-power mode: (1) change-of-state on any enabled SG/SP input, (2) falling edge on INT_B pin from external system event, and (3) edge on CS_B pin (tCSB_WAKEUP = 755–1000 µs). All wake events trigger immediate transition to Normal mode and assert INT_B to notify the MCU.
Is the MC33978AEK pin-compatible with other variants in the 33978 family?
Yes - the MC33978AEK shares identical pinout and register mapping with MC33978EK, MC33978AES, MC34978AEK, and MC34978AES. All SOICW-EP variants (AEK/EK suffixes) are mechanically and electrically interchangeable; QFN variants (AES suffixes) require PCB redesign but maintain functional equivalence and firmware compatibility.
MC33978AEK Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- 32-SSOP (0.295", 7.50mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Multiple Switch Detection
- Interface:
- SPI
- Voltage - Supply:
- 3V ~ 5.25V
- Supplier Device Package:
- 32-SOIC-EP
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
MC33978AEK FAQ
1.How can I place an order for MC33978AEK through Aetrix?
Please submit a Request for Quotation (RFQ) for MC33978AEK 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 MC33978AEK reliable?
The price and inventory of MC33978AEK are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC33978AEK is usually 5 days.
3.What payment methods are accepted for MC33978AEK?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC33978AEK transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC33978AEK?
MC33978AEK orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC33978AEK 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 MC33978AEK?
For technical support, including MC33978AEK datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC33978AEK requirements.
6.How does Aetrix verify that MC33978AEK is sourced from the original manufacturer or authorized distributors?
All MC33978AEK 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 MC33978AEK meets industry standards.
7.What is the process for return or replacement of MC33978AEK?
All MC33978AEK units undergo pre-shipment inspection (PSI). If there is an issue with MC33978AEK, 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 MC33978AEK part is unused and in its original packaging.
Return procedure for MC33978AEK:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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