The 33975 Multiple Switch Detection Interface with Suppressed Wakeup
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).
The device also features a 22-to-1 analog multiplexer for reading
inputs as analog.
The 33975 device has two modes of operation, Normal and Sleep.
Normal mode allows programming of the device and supplies switch
contacts with pull-up or pull-down current as it monitors the switch
change of state. The Sleep mode provides low quiescent current,
which makes the 33975 ideal for automotive and industrial products
requiring low sleep state currents.
Improvements are a programmable interrupt timer for Sleep mode that
can be disabled, switch detection currents of 32 mA and 4.0 mA for
switch-to-ground inputs, and an interrupt bit that can be reset. This
device is powered using SMARTMOS technology.

Features
• Designed to operate from 5.5 V VPWR 28 V
• Switch input voltage: (33975: -14 to 38 V) (33975A: -14 to 40 V)
• Interfaces to microprocessor using 3.3 V/5.0 V SPI protocol
• Selectable wake-up on change of state
• 14 switch-to-ground inputs
• 8 programmable inputs (switches to battery or ground)
• Selectable wetting current (32 mA or 4.0 mA for switch-to-ground inputs)
• Sleep State current VPWR 100 A, VDD 20 A

Applications
• Automotive systems
• Industrial control systems
• Process control systems
• Security systems
• Systems requiring switch status verification for
safety, operation, or process control purposes