MCZ33298EGR2 Freescale, MCZ33298EGR2 Datasheet - Page 21

• Manufacturer Part Number: MCZ33298EGR2
• Manufacturer: Freescale

Specifications of MCZ33298EGR2

• Switch Type: Low Side
• Power Switch Family: MCZ33298
• Input Voltage: -0.3 to 7V
• Power Switch On Resistance: 400mOhm
• Output Current: 1A
• Number Of Outputs: 8
• Mounting: Surface Mount
• Supply Current: 1uA
• Package Type: SOIC W
• Operating Temperature (min): -40C
• Operating Temperature Classification: Automotive
• Pin Count: 24
• Power Dissipation: 3W
• Lead Free Status / RoHS Status: Compliant

current) condition is removed or thermal shutdown is
reached.
shutdown circuitry. Consider a load short (output short to
supply) occurring on an output before, during, and after
output turn ON. When the CS signal rises to the high logic
state, the corresponding output is turned ON, activating a
delay timer. The duration of the delay timer is 70 to 250µs. If
the short circuit takes place before the output is turned ON,
the delay experienced is the entire 70 µs to 250µs followed
by shutdown. If the short occurs during the delay time, the
shutdown still occurs after the delay time has elapsed.
However, if the short circuit occurs after the delay time,
shutdown is immediate (within 20µs after sensing). The
purpose of the delay timer is to prevent false faults from being
reported when switching capacitive loads.
disabled when an over-current is detected. The specific
output will, within 5.0 to 10µs of encountering the short-
circuit, go into an analog current limited mode. This feature is
especially useful when switching incandescent lamp loads,
where high in-rush currents experienced during startup last
for 10 to 20 milliseconds.
shutdown circuitry. Over-temperature, and the over-voltage
faults are not affected by the SFPD pin’s state.
incorporated for short fault detection with actual detection
occurring slightly after the onset of current limit. The current
limit circuitry incorporates a SENSEFET™ approach to
measure the total drain current. This calls for the current
through a small number of cells in the power MOSFET to be
measured and the result multiplied by a constant, giving the
total current. Wherein output shutdown circuitry measures
the drain-to-source voltage, shutting down the output if its
threshold (V
output voltage and comparing it to V
requires a voltage of 0.6 times 4.5V (the minimum V
voltage) or 2.7V to be sensed. For an enabled output, with
V
detected as a “short”, while voltages less than 2.7V will not be
detected as “shorts”.
OVER-CURRENT RECOVERY
normal operation automatically after the short-circuit is
removed (unless thermal shutdown has occurred).
occurs, removing the short circuit will result in the output
remaining OFF until the next write cycle. If the short circuit is
not removed, the output will turn ON for the delay time (70 to
250µs) and then turn OFF for every write cycle commanding
a turn ON.
Analog Integrated Circuit Device Data
Freescale Semiconductor
DD
Grounding the SFPD pin enables the short fault protection
If the SFPD pin is at 5.0V, or V
Each output of the 33298 has its own over-current
Both load current sensing and output voltage sensing are
Short fault detection is accomplished by sensing the
If the SFPD pin is in a high logic state, the circuit returns to
If the SFPD pin is grounded and over-current shutdown
= 5.0 ± 0.5V, an output voltage in excess of 4.4V will be
Thres
) is exceeded.
DD
, an output will not be
Thres
. The lowest V
DD
Thres
SFPD PIN VOLTAGE SELECTION
activation of the short fault protection (i.e., shutdown) mode
equally for all eight outputs, the load having the longest
duration of in-rush current determines what voltage (state)
the SFPD pin should be. Usually if at least one load is, an
incandescent lamp for example, the in-rush current on that
input will be milliseconds in duration. Therefore, setting SFPD
at 5.0V will prevent shutdown of the output due to the in-rush
current. The system relies only on the over-temperature
shutdown to protect the outputs and the loads. The 33298
was designed to switch GE194 incandescent lamps, or
equivalents, with the SFPD pin in a grounded state.
Considerably larger lamps can be switched with the SFPD
pin held in a high logic state.
(current limiting of the output) followed by an immediate over-
current shutdown is necessary. This can be accomplished by
programming the SFPD pin to 5.0V for the extended delay
period, allowing the outputs to remain ON in a current limited
mode, then grounding it to accomplish the immediate
shutdown after a period of time. Additional external circuitry
is required to implement this type of function. An MCU
parallel output port can be devoted to controlling the SFPD
voltage during and after the delay period, is often a much
better method. In either case, care should be taken to
execute the SFPD start-up routine every time start-up or
reset occurs.
UNDER-VOLTAGE SHUTDOWN
shutdown of all outputs. The under-voltage threshold is
between 2.5V and 3.5V. When V
threshold, all outputs are turned OFF, thereby resetting the
Serial Output Data register to indicate the same.
output shutdown and reset. When V
9.0V, the outputs will operate per the command word.
However, the status as reported by the SO pin may not be
accurate below 9.0V V
voltages below 5.5V are not be guaranteed.
DECIPHERING FAULT TYPE
system fault has occurred. With eight outputs having open
load, over-current, over-temperature, and over-voltage faults;
a total of 25 different faults are possible. The SO status word
received by the MCU will be compared with the word sent to
the 33298 during the previous write cycle. For a specific
output, if the SO bit compares with the corresponding SI bit
of the previous word; the output is operating normal with no
fault. Only when the SO bit and previous word SI bit differ is
there a fault indicated. If the two words are not the same, the
MCU should be programmed to determine which output or
outputs are faulted.
logic high, the output would be programmed to be OFF; if,
Since the voltage condition of the SFPD pin controls the
Sometimes both a delay period greater than 70 to 250µs
An under-voltage V
An under-voltage condition at the VPWR pin will not cause
The 33298 SO pin can be used to determine what kind of
If, for a specific output, the initial SI command bit were
DD
PWR
condition will result in the global
. Proper operation at V
FUNCTIONAL DESCRIPTION
DD
FAULT LOGIC OPERATION
PWR
goes below the
is between 5.5V and
PWR
33298
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