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MC33975A

Multiple Switch Detection Interface with Suppressed Wake-up and 32 mA Wetting Current

Freescale Semiconductor 

Freescale Semiconductor

Technical Data

Document Number: MC33975

Rev 11.0, 01/2014

Multiple Switch Detection

Interface with Suppressed

Wake-up and 32 mA Wetting

Current

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 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

33975

33975A

MULTIPLE SWITCH

DETECTION INTERFACE WITH

SUPPRESSED WAKE-UP

EK SUFFIX (PB-FREE)

98ASA10556D

32-PIN SOICW EP

Applications

• Automotive systems

• Industrial control systems

• Process control systems

• Security systems

• Systems requiring switch status verification for

safety, operation, or process control purposes

VDD

VBAT

VBAT

33975

SP0

VPWR

SP1

VDD

VBAT

VDD

POWER SUPPLY

LVI

ENABLE

SP7

WAKE

SG0

SG1

SG12

SG13

SI

SCLK

CS

SO

INT

AMUX

GND

MCU

MOSI

SCLK

CS

MISO

INT

AN0

WATCHDOG

RESET

Figure 1. 33975 Simplified Application Diagram

© Freescale Semiconductor, Inc., 2005 - 2014. All rights reserved.

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