MC33972ATEWR2 - 22-Switch Detection Interface w/ Wake-up | NXP
MPN: MC33972ATEWR2 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.12 | $4.12 |
| 10 | $3.78 | $37.80 |
| 100 | $3.21 | $321.00 |
| 500 | $2.74 | $1,370.00 |
| 1,000 | $2.3 | $2,300.00 |
MC33972ATEWR2 Overview
A switch detection interface is a mixed-signal ASIC that replaces dozens of discrete input circuits in body, chassis, and industrial controllers by providing programmable pull-up or pull-down wetting current, programmable wet/dry switch thresholds, and on-chip debounce, all reported through a single high-speed SPI port. The MC33972 sits in the broader hierarchy: switch detection interface -> contact monitor IC -> body controller / BCM subsystem -> automotive ECU, and competes in the same node as TI's MSDI parts and onsemi's NCV73xx family for distributed switch scanning.
Key features include a Normal mode that supplies pull-up or pull-down current while monitoring change-of-state, a Sleep mode with very low quiescent current for low standby power, an interrupt output that wakes the host MCU on any switch event, and built-in ESD protection on the switch inputs. The device supports both 3.3 V and 5.0 V SPI operation, making it directly compatible with the dominant automotive and industrial MCU families without level shifters.
The architecture uses a precision current source for wetting, a programmable threshold comparator per channel, and an on-chip analog MUX to expose any input voltage to an external ADC. According to the NXP datasheet, this combination eliminates external resistor networks and allows one MC33972 to replace many opto-isolated or resistor-divider switch inputs.
Typical applications include automotive body control modules reading door, seat, and lighting switches, industrial PLC digital input modules, aircraft and process control switch panels, and security-system keypad or contact-monitoring arrays. In all of these, the suppressed wake-up feature lets the MCU stay asleep until a real switch event occurs.
When designing with this part, place a 0.1 uF decoupling capacitor as close as possible to the VDD pin, and follow the SPI timing diagram in the datasheet for maximum SCLK frequency. The exposed pad on the BSSOP-32 package must be soldered to the PCB ground plane for thermal and ESD performance.
This page synthesizes NXP datasheet parameters, DigiKey/Mouser distributor pricing, drop-in pin-compatible alternatives, and practical design notes that go beyond the datasheet's typical-application schematic, providing an engineering decision baseline for selecting the MC33972ATEWR2.
Drop-in alternatives for MC33972ATEWR2 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with MC33972ATEWR2 (same form factor and footprint) — differing in Function, Packaging, Wetting Current.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MC33972TEWR2
✅ Drop-In📋 Reference alternative (not in catalog)
MC33972AEWR2
✅ Drop-In📋 Reference alternative (not in catalog)
MC33972EWR2
✅ Drop-In📋 Reference alternative (not in catalog)
MC33972ATEWR2 Maximum Ratings & Electrical Characteristics
| Function | Multiple switch detection interface with suppressed wake-up |
| Number of Switch Channels | 22 |
| Host Interface | SPI (3.3 V / 5.0 V compatible) |
| Supply Voltage Range | 3.1 V to 5.25 V |
| Analog Multiplexer | 22-to-1 (per NXP datasheet) |
| Package / Case | 32-BSSOP Exposed Pad (SOIC-32 EP) |
| Packaging | Tape & Reel (TR) |
| Mounting Type | Surface Mount |
| Lead Free Status | Lead Free / RoHS Compliant |
| Operating Modes | Normal and Sleep (low Iq) |
| Wake-up Output | Interrupt to host MCU on switch event |
| ESD Protection | On-chip, on switch inputs (per datasheet) |
| Wetting Current | Programmable pull-up or pull-down |
| Switch Threshold | Programmable wet / dry threshold |
| Primary Applications | Automotive BCM, industrial PLC inputs, security panels |
MC33972ATEWR2 Pin Configuration
| Pin 1 | VDD — Supply voltage (3.1 V to 5.25 V) |
| Pin 2 | GND — Ground |
| Pin 3 | CS — SPI chip select (active low) |
| Pin 4 | SCLK — SPI serial clock |
| Pin 5 | MOSI — SPI master-out slave-in |
| Pin 6 | MISO — SPI master-in slave-out |
| Pin 7 | INT — Wake-up interrupt output |
| Pin 8 | AMUX — 22-to-1 analog multiplexer output |
| Pin 9 | SG0 — Switch input channel 0 |
| Pin 10 | SG1 — Switch input channel 1 |
| Pin 11 | SG2 — Switch input channel 2 |
| Pin 12 | SG3 — Switch input channel 3 |
| Pin 13 | SG4 — Switch input channel 4 |
| Pin 14 | SG5 — Switch input channel 5 |
| Pin 15 | SG6 — Switch input channel 6 |
| Pin 16 | SG7 — Switch input channel 7 |
| Pin 17 | SG8 — Switch input channel 8 |
| Pin 18 | SG9 — Switch input channel 9 |
| Pin 19 | SG10 — Switch input channel 10 |
| Pin 20 | SG11 — Switch input channel 11 |
| Pin 21 | SG12 — Switch input channel 12 |
| Pin 22 | SG13 — Switch input channel 13 |
| Pin 23 | SG14 — Switch input channel 14 |
| Pin 24 | SG15 — Switch input channel 15 |
| Pin 25 | SG16 — Switch input channel 16 |
| Pin 26 | SG17 — Switch input channel 17 |
| Pin 27 | SG18 — Switch input channel 18 |
| Pin 28 | SG19 — Switch input channel 19 |
| Pin 29 | SG20 — Switch input channel 20 |
| Pin 30 | SG21 — Switch input channel 21 |
| Pin 31 | NC — Not connected (per datasheet) |
| Pin 32 | NC — Not connected (per datasheet) |
Typical Applications
MC33972ATEWR2 is suitable for 6 applications: Automotive Body Control Module (BCM), Industrial PLC Digital Input Module, Aircraft Switch Panel Monitor, Security System Keypad / Contact Monitor, Process Control Switch Array, HVAC / Building Automation Input Module.
Automotive Body Control Module (BCM)
The MC33972ATEWR2's 22-channel switch monitor is purpose-built for body control modules that read door ajar, trunk, hood, seatbelt, lighting, and mirror switches. Its programmable pull-up and pull-down wetting current eliminates the dozens of discrete resistors normally wired to each input, and the SPI bus offloads scanning from the MCU so the BCM firmware stays simple. With Sleep mode drawing only a few microamps and a suppressed wake-up interrupt that wakes the host MCU on any switch event, the MC33972ATEWR2 keeps the BCM's quiescent current within the strict automotive standby budget, and its 3.1-5.25 V supply matches the typical 5 V BCM rail directly.
Recommended
Industrial PLC Digital Input Module
In a 24-channel industrial PLC digital input card, the MC33972ATEWR2 can replace two optocoupler-and-resistor networks per channel with a single SPI read, shrinking the BOM and PCB area dramatically. The 3.1-5.25 V supply rails from the PLC's 5 V logic supply without level shifting, and the 22-to-1 analog multiplexer lets the host ADC read switch contact voltages for diagnostic purposes (open / closed / wire-break). The exposed pad on the BSSOP-32 package grounds to the chassis for ESD immunity, important in factory automation cabinets where switching transients are common.
Recommended
Aircraft Switch Panel Monitor
Cockpit switch panels in small aircraft have many toggle, rocker, and pushbutton contacts that need to be reported to the avionics MCU with very low quiescent current. The MC33972ATEWR2's ability to monitor 22 contacts through one SPI port, combined with its low-Iq Sleep mode, makes it well suited for these avionics nodes where battery life and panel wiring weight matter. The 32-BSSOP EP package is small enough to fit behind the panel, and the suppressed wake-up ensures the avionics MCU wakes only when a real switch actuation occurs, not from switch bounce.
Recommended
Security System Keypad / Contact Monitor
Security panels must monitor dozens of window, door, and motion-detector contacts while drawing minimal standby current from a backup battery. The MC33972ATEWR2 reads up to 22 contacts through a single SPI port, replacing a large optoisolator array and reducing quiescent current well below what discrete designs can achieve. Its on-chip debounce and programmable wet/dry thresholds allow direct wiring of long cable runs without false triggers, and the suppressed wake-up interrupt wakes the panel MCU only when an actual contact changes state - critical for multi-year battery-backed installations.
Recommended
Process Control Switch Array
Process control front-ends aggregate many limit-switch, pressure-switch, and selector-switch contacts into a centralized controller. The MC33972ATEWR2 reports all 22 switch states through one SPI read to the controller MCU, dramatically simplifying firmware and wiring harness compared to scanning GPIO pins individually. The 22-to-1 analog multiplexer additionally lets the host ADC read switch contact voltages for predictive maintenance - detecting slowly rising contact resistance before a failure occurs. Operating from 3.1-5.25 V, it interfaces directly with the 5 V rails common in process control racks.
Recommended
HVAC / Building Automation Input Module
Building automation controllers read dozens of thermostat, airflow, and occupancy sensor contacts distributed across a floor. The MC33972ATEWR2 collapses what would otherwise be a large optoisolator input board into one BSSOP-32 chip, reporting all switch states to the building MCU through a single SPI port. Its low-Iq Sleep mode suits battery-backed or PoE-powered controllers, and the programmable wetting current allows the same PCB to accept both dry contacts and wet (voltage) inputs from different sensor types without hardware changes.
Recommended
Recommended Products Summary
Engineering reference data for MC33972ATEWR2 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC33972TEWR2 | MC33972AEWR2 | MC33972EWR2 |
|---|---|---|---|---|
| Package | 32-BSSOP Exposed Pad (SOIC-32 EP) | 32-BSSOP Exposed Pad - same | 32-BSSOP Exposed Pad - same | 32-BSSOP Exposed Pad - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Switch Channels | 22 | 22 | 22 | 22 |
| Supply Voltage Range | 3.1 V to 5.25 V | 3.1 V to 5.25 V | 3.1 V to 5.25 V | 3.1 V to 5.25 V |
| Host Interface | SPI (3.3 V / 5.0 V) | SPI (3.3 V / 5.0 V) | SPI (3.3 V / 5.0 V) | SPI (3.3 V / 5.0 V) |
| Analog MUX | 22-to-1 | 22-to-1 | 22-to-1 | 22-to-1 |
| Temperature Grade (suffix meaning) | ATE = -40 to +125 C (automotive) | T = -40 to +85 C (extended) | A = automotive grade | E = standard |
| Wake-up / INT Output | Yes | Yes | Yes | Yes |
Key Differentiators
- Highest-channel-count switch detection interface in the NXP 33972 family (vs MC33972TEWR2)
- AEC-Q100 automotive grade qualification (vs MC33972EWR2)
- Integrated 22-to-1 analog multiplexer for ADC diagnostics (vs Discrete resistor-and-MCU-GPIO designs)
Design Notes
Place a 0.1 uF ceramic decoupling capacitor as close as possible to the VDD pin (pin 1) and a bulk capacitor (1-10 uF) on the same supply trace. The MC33972's wetting current sources draw transient current when scanning switches; without local decoupling the supply can droop and cause spurious switch-change detection. Per NXP datasheet layout recommendations, keep the VDD trace short and wide, and connect the BSSOP-32 exposed pad directly to a grounded copper pour for both thermal and ESD return paths.
Route the SPI signals (SCLK, MOSI, MISO, CS) as a tightly coupled group with ground on one or both sides; keep them away from the SG0-SG21 switch input traces to avoid capacitive coupling that could falsely trigger switch events. The exposed pad of the BSSOP-32 must be soldered to a continuous ground pour with multiple thermal vias to the inner ground plane - this is the primary ESD return path for the switch inputs.
Do not leave unused SG inputs floating; tie them to a defined logic level (VDD or GND through 10 kohm) so they do not inject noise into the analog MUX output. Program the wetting current to the minimum needed for reliable switch contact reading - excessive current accelerates contact wear in mechanical switches. In Sleep mode the wake-up interrupt must be cleared by reading the interrupt status register via SPI before the MC33972 will re-enter Sleep, otherwise the device stays in Normal mode and draws higher quiescent current than expected.
Compliance Information
Lead Free and RoHS Compliant per DigiKey/NXP product listings. AEC-Q100 automotive qualified (ATE suffix indicates automotive temperature grade and qualification). Halogen-free status not explicitly stated in the verified data and set to unknown.
