33972_09 Datasheet, PDF (12/32 Pages) Freescale Semiconductor, Inc – Multiple Switch Detection Interface with Suppressed Wake-up

FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
MC33972 - Functional Block Diagram
Control & Protection
Bandgap
Temp. Sense
Voltage Regulation
Oscillator & Clock
Switch Programmable
Inputs
SP0 - SP7
Interface & Control
SPI Interface
Interrupt/Wake-up
Multiplex Control
Switch–to-Ground
Inputs
SG0 - SG13
Control & Protection Interface & Control SW Prog Inputs SW-GND Inputs
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.
33972
12
Analog Integrated Circuit Device Data
Freescale Semiconductor