TYPICAL APPLICATION
STANDALONE MODE
All protection functions are available without SPI
This section consists of evaluating the MC33874
standalone capability.
communication. Nevertheless, any configuration is possible
without an MCU to communicate by SPI. Some functions still
enable, but diagnosis is reduced. Available functions and
default parameters are detailed next.
CONFIGURATION WITHOUT MCU
The standalone mode is intended for customers who
desire to plug the device and then immediately “play” with it,
without having to connect it to a microcontroller. It also
provides an easy way to evaluate the main electrical features.
FUNCTIONING WITHOUT MCU
Without an MCU, SPI communication is not possible. Fail-
safe Mode and watchdog timeout are not useful functions
without an MCU, but still enable. Wake/Sleep Mode is used
to minimize current consumption during Sleep Mode. IN pins
control the corresponding outputs and FS output is active (at
0V) when a default occurs.
Without the Microcontroller to select programmable
parameters and get full diagnosis via the SPI, the MC33874
runs with all parameters set to default.
The input SPI pins and VDD must be connected to ground.
Fail-safe Mode and watchdog timeout must be disabled by
connecting the FSI to GND.
The tables 1 and 2 illustrate the available functions without
SPI and default parameters.
Table 1. Available Functions
Function
Wake/Sleep Mode
With SPI
Without SPI
Available
Available
Output ON/OFF control
Over-temperature protection
Over-voltage protection
Under-voltage protection
Over-current protection
Via SPI or IN pin
Only with IN pin
Available
Available, can be unlatched
Available, can be disabled
Available, can be disabled
Available, always enable
Available, always enable
Available, configurable (with 8 low levels and Available, always enable with default values
2 high levels), can be disabled
Open load, battery disconnect, reverse
battery, ground disconnect protections
Available
Available
Fault diagnosis
Full diagnosis with report by SPI and fault
status pin (/FS)
Limited fault diagnosis with Fault status pin
only
Current sense
Available, 2 configurable ratios
Available, 4 configurable timings
2 slew rate modes
Not available
Watchdog timeout
Available, default value
Default slew rate mode
Available
Configurable slew rate
Analog temperature feedback
Available
Table 2. Default SPI-configurable parameters
Configulable parameter
Default typical value
Over-voltage protection
Under-voltage protection
Over-current protection
Over-current low level
Over-current high level
Over-current detect blanking time
Current sense
Enable
Enable
Enable
OCLO0
OCHI0
tOCLO0
Disable
TWDTO0
Slow mode
Watchdog time timeout
Slew rate mode
Table 2 illustrates default parameters after resetting or
applying supply voltage to the MC33874. Levels and timings
are typical values.
33874
Analog Integrated Circuit Device Data
Freescale Semiconductor
29
FREESCALE [ Freescale ]
