33888 Datasheet, PDF (26/40 Pages) Freescale Semiconductor, Inc – Quad High-Side and Octal Low-Side Switch for Automotive

FUNCTIONAL DEVICE OPERATION
PROTECTION AND DIAGNOSTIC FEATURES
Table 10. Serial Output Bit Assignment (continued)
OD5 Reports the absence or presence of a fault on LS5.
OD4 ^{Reports the absence or presence of a fault on LS4.}
OD3 ^{Reports the absence or presence of a fault on HS3.}
OD2 Reports the absence or presence of a fault on HS2.
OD1 ^{Reports the absence or presence of a fault on HS1.}
LSB OD0 ^{Reports the absence or presence of a fault on HS0.}
LSB OD0 Reports the absence or presence of a fault on HS0.
The MC33888 device reports the occurrence of the
following faults via the output dedicated bits clocked out of
the SO pin:
• Over voltage
• Open Load
• Over temperature
In the event of an occurrence of faults, the bits clocked out
of the device will indicate the presence of a fault with a logic
[1] on the output dedicated bit, prior to and since the last SPI
communication, or at the time of the CSB pin going to logic
[0]. Each type of fault can be differentiated from the others as
follows:
OVER VOLTAGE
An over voltage occurrence can be inferred if all twelve bits
representing each of the outputs are logic [1] at the same
time.
OPEN LOAD
An open load condition is only detected when the output is
off and the open load detection for the output of concern is
enabled. The first SPI read after the output is commanded on
will clear the fault bit for this output.
OVER TEMPERATURE
An over temperature condition is indicated and latched
into the fault register if the output is on and the indicating
output experienced an over temperature event since the last
SPI write. Each output has a dedicated temperature sensor.
The high side drivers will turn off after the over temperature
shutdown level is reached until the temperature falls below
the specified hysteresis level and then will turn back on
automatically, unless the output has been commanded off. In
either case, a fault indication for the faulted output will be
present for the next SPI read.
CURRENT LIMIT
An output which current limits will not indicate a fault
unless the limitation results in enough power dissipation to
increase the temperature of the limiting transistor to its over
temperature shutdown level.
Each of these faults are indicated real time by the FLTB
pin, which could be used as an initial indication of the
presence of a fault within the device. Determining the actual
faulted output would requires an analysis of the fault bits
provided by the device via the SO pin.
Note that the very first SPI read after the battery falls below
6V may not be correct, if the VDD remained in specification
and a reset was not generated by the MCU.
PROTECTION AND DIAGNOSTIC FEATURES
REVERSE BATTERY REQUIREMENTS
The low-side and high-side outputs survive the application
of reverse battery as low as -16 V.
GROUND DISCONNECT PROTECTION
In the event that the 33888 ground is disconnected from
load ground, the device protects itself and safely turns OFF
the outputs, regardless of the state of the output at the time
of disconnection.
33888
26
Analog Integrated Circuit Device Data
Freescale Semiconductor