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Analog Integrated Circuit Device Data
14
Freescale Semiconductor
33975
FUNCTIONAL DESCRIPTIONS
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
Figure 7. Functional Internal Block Description
ANALOG CONTROL AND PROTECTION
CIRCUITRY:
The 33975 is designed to operate from 5.5 V to 38/40 V on
the VPWR pin. 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 pin. The VDD supply
pin 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.
MCU INTERFACE AND CONTROL:
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.
SWITCH PROGRAMMABLE INPUTS:
Programmable switch detection inputs. These 8 inputs can
selectively detect switch closures to ground or battery. The
33975 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.
MC33975 - Functional Block Diagram
Programmable
Monitor Inputs
SP0 - SP7
Analog Control
and Protection Circuitry
Voltage Regulation
Bandgap
MCU Interface and Control
Multiplex Control
Control & Protection
Monitor
Interface & Control
Monitor Inputs
SG0 - SG13
Oscillator & Clock
Temp. Sense
Interrupt/Wake-up
SPI Interface
Prog. Monitor