MCZ33291LEG Freescale Semiconductor, MCZ33291LEG Datasheet - Page 17

• Manufacturer Part Number: MCZ33291LEG
• Description: IC SWITCH 8X LOSIDE W/SPI 24SOIC
• Manufacturer: Freescale Semiconductor
• Type: Low Sider

Specifications of MCZ33291LEG

• Input Type: SPI
• Number Of Outputs: 8
• On-state Resistance: 1.1 Ohm
• Current - Output / Channel: 500mA
• Current - Peak Output: 3A
• Voltage - Supply: 9 V ~ 26.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

FAULT LOGIC OPERATION
INTRODUCTION
operation by comparing the command 8-bit word to the status
8-bit word. Assume after system reset, the MCU first sends
an 8-bit command word to the 33291L. This word is called
Command Word 1. Each output to be turned ON will have its
corresponding data bit low. Refer to the data transfer timing
illustration in
of the 33291L, a status word is being simultaneously written
and received by the MCU. However, the word being received
by the MCU is the status of the previous write word to the
33291L, Status Word 0. If the command word of the MCU is
written a second time (Command Word 2 = Command Word
1), the word received by the MCU, Status Word 2, is the
status of Command Word 1. The timing diagram illustrated in
Figure 17
compared with Command Word 1. The MCU will Exclusive
OR Status Word 2 with Command Word 1 to determine if the
two words are identical. If the two words are identical, no
faults exist. The timing between the two write words must be
greater than 100 s to receive proper drain status. The
system data bus integrity may be tested by writing two like
words to the 33291L within a few microseconds of each
other.
INITIAL SYSTEM SETUP TIMING
word to the 33291L. If the word is repeated within
approximately five microseconds of the first word, the word
received by the MCU, at the end of the repeated word, serves
as a confirmation of data bus integrity (1). At startup, the
33291L will take 25 s to 100 s before a repeat of the first
word should be repeated at least 100 s later to verify the
status of the outputs.
The four possible faults are:
Analog Integrated Circuit Device Data
Freescale Semiconductor
1. Communication errors on the data bus
2. Actual faults of the output loads
1. Overtemperature
2. Output OFF Open Fault
3. Short Fault (overcurrent)
4. V
The MCU can perform a parity check of the fault logic
As Command Word 1 is being written into the Shift register
The MCU can monitor two kinds of faults:
After initial system startup or reset, the MCU will write one
The SO of the 33291L will indicate any one of four faults.
PWR
depicts this operation. Status Word 2 is then
Overvoltage Fault
Figure
17.
faults are output specific. Overtemperature Detect, Output
OFF Open Detect, and Output Short Detect are dedicated to
each output separately such that the outputs are independent
in operation. A V
causing all outputs to be turned OFF.
OVERTEMPERATURE FAULT
circuits are specifically incorporated for each individual
output. The shutdown following an Overtemperature
condition is independent of the system clock or any other
logic signal. Each independent output shuts down at 155°C
to 185°C. When an output shuts down due to an
Overtemperature Fault, no other outputs are affected. The
MCU recognizes the fault since the output was commanded
to be ON and the status word indicates it is OFF. A maximum
hysteresis of 20°C ensures an adequate time delay between
output turn OFF and recovery. This avoids a very rapid turn
ON and turn OFF of the device around the Overtemperature
threshold. When the temperature falls below the recovery
level for the Overtemperature Fault, the device will turn ON
only if the Command Word during the next write cycle
indicates the output should be turned ON.
OVERVOLTAGE FAULT
33291L to shut down all outputs until the overvoltage
condition is removed and the device is re-programmed by the
SPI. The overvoltage threshold on the V
as 28 V to 36 V with 1.0 V typical hysteresis. Following the
overvoltage condition, the next write cycle sends the SO pin
the hexadecimal word $FF (all ones), indicating all outputs
are turned OFF. In this way, potentially dangerous timing
problems are avoided and the MCU reset routine ensures an
orderly startup of the loads. The 33291L does not detect an
overvoltage on the V
the Motorola 33161 Universal Voltage Monitor, is necessary
to accomplish this function.
OUTPUT OFF OPEN LOAD FAULT
reporting of an open load when the corresponding output is
disabled (input bit programmed to a logic high state). To
understand the operation of the Open Load Fault detect
circuit, see
detected by comparing the drain voltage of the specific
MOSFET output to an internally generated reference. Each
output has one dedicated comparator for this purpose.
With the exception of the Overvoltage Fault, all of these
Patent pending Overtemperature Detect and shutdown
An Overvoltage condition on the V
An Output OFF Open Load Fault is the detection and
Figure
PWR
18. The Output OFF Open Load Fault is
Overvoltage Detect is of a global nature,
DD
pin. Other external circuitry, such as
FUNCTIONAL DESCRIPTION
PWR
PWR
pin causes the
pin is specified
33291L
17