The 33975 Multiple Switch Detection Interface with Suppressed Wake-up 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 32mA and 4.0mA for switch-to-ground inputs, and an interrupt bit that can be reset.

Features
• Designed to operate from 5.5V ≤ VPWR ≤ 28V
• Switch input voltage: (33975: -14 to 38V) (33975A: -14 to 40V)
• Interfaces to microprocessor using 3.3V/5.0V 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 (32mA or 4.0mA for switch-to-ground
   inputs)
• Sleep State current VPWR 100μA, Vdd 20μA
• Pb-free packaging designated by suffix code EK