MC33978 Switch Detection Interface Evaluation Kit

The MC33978 is a multiple switch detection interface (MSDI) device which is designed to detect the closing and opening of up to 22 switch contacts. The switch status, either open or closed, is transferred to the microprocessor unit (MCU) through a serial peripheral interface (SPI) in automotive environments. This SMARTMOS device features a 24-to-1 analog multiplexer for reading analog inputs. The analog input signal is buffered and provided on the analog multiplexer (AMUX) output pin for the MCU to read. Individually selectable input currents are available in Normal and Low-Power Mode (LPM), as needed in the application. A battery and temperature monitor are included in the IC and available via the AMUX pin. This product interfaces with any microcontroller that supports SPI communications (Freescale or competitor).

Designed to operate 4.5 V = V_BATP = 36 V

Switch input voltage range -14 V to V_PWR, 36 V Max.

Interfaces directly to an MCU using 3.3 V / 5.0 V SPI protocol

• Selectable wake-up on change of state
• Selectable wetting current (2, 6, 8, 10, 12, 14, 16, or 20 mA)

8 programmable inputs (switches to battery or ground) and 14 switch-to-ground inputs

Typical standby current - V_BATP = 30 uA and V_DD = 10 uA

Integrated battery and temperature sensing