Multiple Switch Detection Interface

The 33993 Multiple Switch Detection Interface 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 analog input signal is buffered and provided on the AMUX output pin for the MCU to read.
The 33993 device has two modes of operation, Sleep and Normal. The Sleep mode provides low quiescent current and enables the wake-up features of the device. Normal mode allows programming of the device and supplies switch contacts with pull-up or pull-down current as it monitors switch change of state.
The 33993 is packaged in the 32-pin wide-body SOIC, reducing circuit board area. Low quiescent current makes the 33993 ideal for automotive and industrial products requiring low sleep state currents. The internal block diagram of the 33993 is illustrated in Figure 1, page 2.

FEATUREs
• Designed to Operate 5.5 V ≤ VPWR ≤ 26 V
• Switch Input Voltage Range -14 V to VPWR, 40 V Max
• Interfaces Directly to Microprocessor Using 3.3 V/5.0 V SPI Protocol
• Selectable Wake-Up on Change of State
• Selectable Wetting Current (16 mA or 2.0 mA)
• 8 Programmable Inputs (Switches to Battery or Ground)
• 14 Switch-to-Ground Inputs
• VPWR Standby Current 100 µA Typical, VDD Standby Current 20 µA Typical
• Active Interrupt (INT) on Change-of-Switch State