33972 datasheet(12/32 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33972

FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

Figure 7. Functional Internal Block Description

CONTROL AND PROTECTION CIRCUITRY:

The 33972 is designed to operate from 5.5 V to 38/40 V on

the VPWR terminal. Characteristics are provided from 8.0 to

28 V for the device. Switch contact currents and the internal

logic supply are generated from the VPWR terminal. The

VDD supply terminal is used to set the SPI communication

voltage levels, current source for the SO driver, and pull-up

current on INT and CS.

The on-chip voltage regulator and bandgap supplies the

required voltages to the internal monitor circuitry. The

temperature monitor is active in the Normal mode.

INTERFACE AND CONTROL:

The 33972 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 33972 device has two modes

of operation, Normal and Sleep.

SWITCH PROGRAMMABLE INPUTS:

Programmable switch detection inputs. These 8 inputs can

selectively detect switch closures to Ground or Battery. The

33972 device has 8 switch inputs capable of being

programmed to read switch-to-ground or switch-to-battery

contacts. The input is compared with a 4.0 V reference.

When programmed to be switch-to-battery, voltages greater

than 4.0 V are considered closed. Voltages less than 4.0 V

are considered open. The opposite holds true when inputs

are programmed as switch-to-ground.

SWITCH–TO-GROUND INPUTS:

Switch detection interface inputs. These 14 inputs can

detect switch closures to ground only. The input is compared

with a 4.0 V reference. Voltages greater than 4.0 V are

considered open. Voltages less than 4.0 V are considered

closed. Note: Each of these inputs may be used to supply

current to sensors external to a module.

MC33972 - Functional Block Diagram

Switch Programmable

Inputs

SP0 - SP7

Control & Protection

Voltage Regulation

Bandgap

Interface & Control

Multiplex Control

Control & Protection

SW-GND Inputs

Interface & Control

Switch–to-Ground

Inputs

SG0 - SG13

Oscillator & Clock

Temp. Sense

Interrupt/Wake-up

SPI Interface

SW Prog Inputs

33972 Datasheet(PDF) 12 Page - Freescale Semiconductor, Inc

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