NXP Semiconductors MC33978EKR2

Overview

MC33978EKR2 from NXP Semiconductors is a 22-channel automotive-grade switch detection interface IC with programmable wetting current, integrated 24:1 analog multiplexer (AMUX), battery/temperature monitoring, and SPI communication. It operates from 4.5 V to 36 V, supports Normal and Low-power modes (IBATP = 30 µA typical in LPM), and interfaces directly with 3.3 V/5.0 V MCUs for vehicle body control modules.

For engineers reviewing the MC33978EKR2 datasheet, MC33978EKR2 pinout, MC33978EKR2 application, or MC33978EKR2 equivalent, this page delivers verified technical context, exact pin functions, real-world use cases in HVAC and gateway systems, and validated alternative parts - all grounded in NXP's Rev. 7.0 specification and SOICW-EP package documentation.

Technical Context

The MC33978EKR2 implements a dual-mode SMARTMOS architecture: Normal mode enables full SPI configuration, wetting current programming (2–20 mA per channel), and active switch state polling; Low-power mode reduces IBATP to 30 µA while retaining wake-on-change capability via INT_B or WAKE_B. Its internal 192 kHz oscillator drives LPM timing with ±15% tolerance.

Switch inputs are partitioned into eight programmable SPx pins (switch-to-battery or ground) and fourteen SGx pins (switch-to-ground only), each with independent wetting/sustain current control. The AMUX block buffers and routes selected analog inputs-including battery voltage (via SG5 divider) and die temperature-to the AMUX output pin for MCU ADC sampling.

Key Specifications

Pinout & Package

MC33978EKR2 is packaged in a 32-pin SOICW-EP (exposed pad) with Pb-free (EK suffix) construction, optimized for thermal dissipation in high-ambient automotive environments. RθJA = 79 °C/W on single-layer board.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switch detection interface applications.

Compared with MC33978AEK and MC34978EK, the MC33978EKR2 offers the tightest AMUX offset specification for general-purpose switch detection and the highest ambient temperature rating - making it optimal for under-hood body control and industrial PLC applications where thermal margin and analog accuracy are balanced.

Availability

MC33978EKR2 is available at Aetrix Electronics and suitable for automotive body control modules, HVAC control panels, and industrial PLC input modules requiring stable component supply, AEC-Q100 qualification, and long-term production continuity.

Supply support for MC33978EKR2 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 focused on automotive, industrial, and IoT applications, with deep expertise in high-reliability analog and mixed-signal solutions.

The MC33978EKR2 belongs to NXP's SMARTMOS family of automotive interface ICs, designed specifically for robust, low-power switch monitoring in harsh environments - enabling simplified wiring harnesses and reduced ECU complexity.

FAQ

What is the maximum number of switch inputs supported by the MC33978EKR2?

The MC33978EKR2 supports up to 22 switch inputs: eight SPx pins (configurable as switch-to-battery or switch-to-ground) and fourteen SGx pins (switch-to-ground only). This configuration is fixed in silicon and cannot be expanded. All 22 channels are monitored simultaneously in Normal mode and selectively polled in Low-power mode.

Does the MC33978EKR2 require external components for basic switch detection operation?

Yes - the MC33978EKR2 requires an external reverse-battery protection diode between battery and VBATP (VF = 0.6–1.0 V), a 100 µF bulk capacitor, and a 100 nF bypass capacitor on VBATP. No external wetting current resistors or debounce RC networks are needed, as these functions are fully integrated within the MC33978EKR2.

How does the AMUX output function in the MC33978EKR2, and what signals can it provide?

The AMUX output pin of the MC33978EKR2 delivers a buffered analog voltage from one of 24 selectable sources: battery voltage (via SG5 ÷6 divider), on-die temperature sensor (8 mV/°C), or any of the 22 switch inputs. Selection is controlled via SPI register writes; the output settles within 20 µs and maintains ±10 mV offset in the EK variant.

What is the wake-up latency from Low-power mode for the MC33978EKR2?

The MC33978EKR2 wakes from Low-power mode in ≤1000 µs when triggered by a falling edge on CS_B, and similarly fast for INT_B or WAKE_B events. This timing is guaranteed across the full VBATP range (4.5 V to 28 V) and ensures responsive system recovery without MCU polling overhead.

Is the MC33978EKR2 pin-compatible with other variants in the 33978 family?

Yes - the MC33978EKR2 shares identical pinout, package dimensions, and register map with MC33978EK, MC33978AEK, MC34978EK, and MC34978AEK. All are 32-pin SOICW-EP devices with the same mechanical and electrical interface, enabling drop-in replacement based on temperature grade or AMUX offset requirements.