Overview
The NXP MC33978AEK is a multiple switch detection interface (MSDI) designed to detect the closing and opening of up to 22 switch contacts. This SMARTMOS device is particularly suited for automotive and industrial applications where low sleep-state currents are crucial. It communicates with a microprocessor unit (MCU) through a serial peripheral interface (SPI) and supports both 3.3 V and 5.0 V SPI protocols.
The device features a 24-to-1 analog multiplexer for reading input channels as analog inputs and includes a battery and temperature monitor accessible via the AMUX pin. It operates in two modes: Normal mode and Low-power mode (LPM), with the latter providing low quiescent current to conserve power.
Key Specifications
| Parameter | Description | Min. | Max. | Unit |
|---|---|---|---|---|
| VBATP (Battery Voltage) | Battery voltage range | -0.3 | 40 | V |
| VDDQ (Supply Voltage) | Supply voltage range | -0.3 | 7.0 | V |
| SGx, SPx (Switch Input Range) | Switch input voltage range | -14 | 38 | V |
| Operating Temperature (TA) | Operating temperature range | -40 | 125 | °C |
| Wetting Current | Selectable wetting current values | 2.0 mA | 20 mA | mA |
| Standby Current (IBATP, IDDQ) | Typical standby current values | 30 μA, 10 μA | μA | |
| Package Type | Package options | SOICW-EP 32 pins, QFN (WF-TYPE) 32 pins |
Key Features
- Detection of up to 22 switch contacts with transfer of switch status to MCU via SPI.
- 24-to-1 analog multiplexer for reading input channels as analog inputs.
- Integrated battery and temperature monitoring accessible via AMUX pin.
- Selectable wetting current (2, 6, 8, 10, 12, 14, 16, or 20 mA).
- Support for 3.3 V / 5.0 V SPI protocol.
- Selectable wake-up on change of state.
- Active interrupt (INT_B) on change-of-switch state.
- Low-power mode (LPM) with low quiescent current.
Applications
The MC33978AEK is ideal for automotive and industrial products that require low sleep-state currents. It is particularly useful in applications such as:
- Automotive systems requiring switch detection and low power consumption.
- Industrial control systems needing multiple switch monitoring.
- Systems requiring integrated battery and temperature sensing.
Q & A
- What is the primary function of the MC33978AEK?
The primary function is to detect the closing and opening of up to 22 switch contacts and transfer the switch status to a microprocessor unit (MCU) via SPI.
- What are the operating voltage ranges for VBATP and VDDQ?
VBATP operates from -0.3 V to 40 V, and VDDQ operates from -0.3 V to 7.0 V.
- What types of packages are available for the MC33978AEK?
The device is available in SOICW-EP 32 pins and QFN (WF-TYPE) 32 pins packages.
- What is the range of selectable wetting currents?
The wetting current can be selected from 2.0 mA to 20 mA in various steps.
- Does the MC33978AEK support low-power mode?
- How does the device communicate with the MCU?
The device communicates with the MCU using a 3.3 V / 5.0 V SPI protocol.
- What additional monitoring features are included in the MC33978AEK?
The device includes integrated battery and temperature monitoring accessible via the AMUX pin.
- What is the typical standby current of the MC33978AEK?
The typical standby current is 30 μA for IBATP and 10 μA for IDDQ.
- Can the MC33978AEK wake up on a change of state?
- Is there an active interrupt feature on the MC33978AEK?
