MC33298DWR2 Freescale Semiconductor, MC33298DWR2 Datasheet - Page 22

• Manufacturer Part Number: MC33298DWR2
• Description: IC OCTAL SERIAL SWITCH 24-SOIC
• Manufacturer: Freescale Semiconductor
• Type: Low Sider

Specifications of MC33298DWR2

• Input Type: SPI
• Number Of Outputs: 8
• On-state Resistance: 350 mOhm
• Current - Output / Channel: 1A
• Current - Peak Output: 4A
• 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: Contains lead / RoHS non-compliant
• Other names: MC33298DWTR

upon the next command word being entered, a logic low
came back on SO, for that specific output’s corresponding bit,
an Output-OFF Open-Load fault would be indicated. The
resulting SO bit, for that specific output, would be different
from that entered during the previous word for that SI bit,
indicating the fault. The eight output-off open-load faults are
therefore most easily detected.
logic low, calling for the output to be programmed on; upon
the next word command being entered, the corresponding bit
came back with a logic high on SO, an output over-current
fault would be indicated. An over-current fault is always
reported by the SO output and is independent of the logic
state existing on the SFPD pin. When the SFPD pin is in a
logic high state, an over-current condition will be reported on
the SO pin. However, limiting output current is in effect and
the output is permitted to operate if the over-current condition
does not drive output into an over-temperature fault. An over-
temperature fault will shutdown the specific output effected
for the duration of the over-temperature condition.
related. Turning the effected output switches OFF and
waiting for some time to allow the output to cool down should
make these types of faults go away. Soft over-current faults
can sometimes be determined over hard short faults and over
temperature faults by observing the time required for the
device to recover. However, in general over-current and over-
temperature faults can not be differentiated in normal
application usage.
faults can be detected with only one (SO) pin being used for
fault status reporting.
will immediately be turned OFF and remain latched off. A new
THERMAL MODEL
generate negligible power. In contrast, the output transistors
take up most of the die area and are the primary contributors
of power generation. The thermal model illustrated in
Figure 22
PC board. The model is accurate for both steady state and
transient thermal conditions. The components R
R
silicon die for transistor outputs 0 through 7, while C
through C
capacitance of the silicone die translator outputs and plastic.
The device area and die thickness determine the values of
these specific components.
mounting flag to the outside environment is represented by
the terms R
resistance of leads and the PC board make up the steady
state package thermal resistance, R
capacitance of the package is made up of the combined
22
33298
FUNCTIONAL DESCRIPTION
FAULT LOGIC OPERATION
D7
If for a specific output, the initial SI command bit were a
Over-current and over-temperature faults are often
An advantage of the synchronous serial output is multiple
If V
Logic functions take up a very small area of the die and
The thermal impedance of the package from the internal
represent the steady state thermal resistance of the
PWR
D7
was developed for the 33298 mounted on a typical
experiences an over-voltage condition, all outputs
PKG
represent the corresponding thermal
and C
PKG
. The steady state thermal
PKG
. The thermal
THERMAL CHARACTERIZATION
D0
through
D0
command word is required to turn the outputs back on
following an over-voltage condition.
OUTPUT VOLTAGE CLAMPING
clamp to provide fast turn-off and transient protection of the
output. Each clamp independently limits the drain to source
voltage to 65V at drain currents of 0.5A and keeps the output
transistors from avalanching by causing the transient energy
to be dissipated in the linear mode. See
energy clamped (E
current area under the current curve (I
voltage (V
non-repetitive method at 0.5A, indicate the maximum energy
to be 50mJ at 150°C junction temperature per output.
capacitance of the flag and the PC board. The mode
compound was not modeled as a specific component but it is
factored into the other overall component values.
ambient temperature the device and PC board are subjected
to.The I
dissipation and is calculated by totalling the power dissipation
of each individual output transistor. This is easily
accomplished by knowing R
individual outputs.
experienced with this thermal model. Tests indicate the
model accuracy to have less than 10 percent error. Output
interaction with an adjacent output is believed to be the main
contributor to the thermal inaccuracy. Tests indicate little or
no detectable thermal affects caused by distant output
transistors isolated by one or more other outputs. Tests were
conducted with the device mounted on a typical PC board
placed horizontally in a 33 cubic inch still air enclosure. The
PC board was made of FR4 material measuring 2.5 by 2.5
Drain-to-Source ON
Drain-to-Source Clamp
Drain Current
Voltage (VCL = 65V)
Voltage (V
Each output of the 33298 incorporates an internal voltage
Characterization of the output clamps, using a single pulse
The battery voltage in the thermal model represents the
Very satisfactory steady state and transient results are
(ID = 0.5A)
PWR
GND
CL
DS(ON)
Figure 21. Output Voltage Clamping
current source represents the total power
) times the duration the clamp is active (t).
)
J
) can be calculated by multiplying the
Analog Integrated Circuit Device Data
Area (I A )
Current
DS(ON)
and load current of the
Freescale Semiconductor
A
) times the clamp
Figure
Drain Voltage
(E
Clamp Energy
J
= I
21. The total
A
x V
CL
VPWR
Time
x t)