MC33298 Motorola, MC33298 Datasheet - Page 19

• Manufacturer Part Number: MC33298
• Description: OCTAL SERIAL SWITCH (SPI Input/Output)
• Manufacturer: Motorola

Latch–Up Immunity
characterized. Latch–up immunity has both a dc and a
transient immunity component. DC latch–up immunity results
indicate the device to be capable of withstanding in excess of
four amps of reverse current out of any of the output
transistors while the control logic continues to function
normally. The logic control current (I DD ) was found to
increase by only 0.6 mA with four amps of current being
pulled out of an output. Additionally, the I PWR current was
found to increase by only 0.15 mA under the same condition.
These increases are a result of minority carriers being
injected into substrate and subsequently being collected.
transient latch–up immunity and has been applied to this
automotive circuit design. Results of transient testing indicate
the device to operate properly at output currents greater than
1.5 A. The procedure tests for the device’s immunity to
intermittent load to battery current connection with the device
controlling an inductive load. Appropriately termed “the file
test,” the battery is connected to a shop file while the lead to
the inductive load is dragged across the files surface causing
intermittent load opens producing lots of arcs, sparks, and
smoke, plus severe transients (see Figure 24). It is during
these severe transients that latch–up most likely could occur.
The battery voltage used for this test was 18 V and the
inductive load was 2.0 mH. These values were found to
produce severe transient stresses of the device outputs. All
outputs must maintain operation and input control during
transient generation to pass “the file test.”
SIOP Communication
microprocessors are the Serial Peripheral Interface (SPI) and
Synchronous Input Output Port (SIOP). SIOP is a subset of
the more flexible SPI and the simpler of the two protocols.
SIOP is used on many of the MC68HC05 family of
microcontrollers. Restrictions of the SIOP protocol include:
1) the SCLK frequency is fixed at one–fourth the internal
clock rate and 2) the polarity of the SCLK signal is fixed.
protocol and is not directly compatible with the serial input
requirements of the MC33298. Specifically, the MC33298
accepts data on the falling edge of SCLK whereas its rising
edge triggers data transfer in the SIOP protocol. SCLK is high
during SIOP transmissions, which is the opposite of what the
MC33298 requires.
protocol, the MC33298 can easily be adapted to
communicate with SIOP protocol through the use of
software. The amount of code required to implement SPI in
software is relatively small, so the only major drawback is a
slower transfer of data. The software routine shown in
Table 1 completes a transfer in about 100 s.
MOTOROLA ANALOG IC DEVICE DATA
Device latch–up caused by substrate injection has been
The following procedure has been developed to test for
Two common communication protocols used in Motorola’s
By way of example, the MC68HC05P9 utilizes SIOP
Though designed specifically for SPI communication
APPLICATIONS INFORMATION
MC33298
stable and were not affected by dc or transient latch–up
immunity testing.
Cost
cost effective octal output serial switch for applications
typically encountered in the automotive and industrial market
segments. To accomplish only the most basic serial switch
function the MC33298 offers, using a discrete semiconductor
approach, would require the use of at least eight logic level
power MOSFETs for the outputs and two shift registers for
the I/O plus other miscellaneous “glue” components.
Additional circuitry would have to be incorporated to
accomplish the protection features offered by the MC33298.
Other noteworthy advantages the MC33298 offers are
conservation of power and board space, requirement of
fewer application components, and enhanced application
reliability. The MC33298 is available at a fraction of the cost
required for discrete component implementation and
represents true value.
advanced performance and features and worthy of
consideration.
Battery
The device’s input control currents were found to remain
The bottom line relates to cost. The MC33298 is a very
The MC33298 represents a cost effective device having
Figure 24. Transient Latch–Up Immunity File Test
SFPD
Reset
SCLK
V DD
CSB
SO
SI
V PWR
0.1 F
Control
Detect
Circuit
Detect
Open
Load
Short
Gate
Temperature
Detect
Over
65 V
I limit
R S
Output 0
Outputs
Grounds
1 – 7
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