mc33812 Freescale Semiconductor, Inc, mc33812 Datasheet - Page 17

• Manufacturer Part Number: mc33812
• Description: Multifunctional Ignition And Injector Driver
• Manufacturer: Freescale Semiconductor, Inc

the logic level LAMPIN input pin. When LAMPIN is high, the
LAMP pin is pulled to ground, turning on an external bulb or
LED. When LAMPIN is low, the bulb or LED pulls the LAMP
output to V
LAMPOUT Protection Features
Over-current (I
separate protection schemes to prevent damage to the
output device.
current event occurs. In this case the current limiting circuitry
will attempt to limit the maximum current flow to the specified
I
Short to Battery
Off State, Open Load Detection
Since there is no way to annunciate an open load fault for the
lamp output driver, no open load fault detection is performed
by the 33812.
On State, Shorted Load Detection
Even though there is no way to annunciate a shorted load
fault for the lamp output driver, shorted fault detection is
voltage event on VPWR is listed in
Analog Integrated Circuit Device Data
Freescale Semiconductor
OUT LIM-LAMP
The second protection scheme is invoked when the over-
current fault is due to a hard short to battery. In this case, the
The Lamp Driver is a low side driver that is controlled by
The LAMPOUT Driver protection scheme uses three
The first protection scheme is deployed when an over-
How the outputs behave after an over-voltage or under-
BAT
value.
, and the lamp is turned off.
OUT-LIM-LAMP
)
OVER/UNDER-VOLTAGE SHUTDOWN STRATEGY
Table 3
LAMPOUT FAULT DETECTION FEATURES
below:
LAMP DRIVER OPERATION
if the fault clears.
Temperature Limit (T
temperature of the output device. Any time the maximum
temperature limit on the output device is exceeded (
device will shutdown until the junction temperature falls below
this maximum temperature minus the hysteresis temperature
value. The
controls the output device regardless of the state of the
LAMPIN input. The device is unable to be activated until the
junction temperature falls below this maximum temperature
minus the hysteresis temperature value.
performed by the 33812 as part of the protection for the
output FET.
time of t
current
Table 3. Over-voltage/Under-voltage Truth Table
LAMPOUT
LAMPOUT
protection circuitry will, after the short detection filter time,
turn off the output driver.
IGNOUT
INJOUT
Output
ROUT
ROUT
There will be an internal retry timer to try to turn on again
There is no annunciation of any LAMPOUT faults.
The third protection scheme deals with the junction
The maximum temperature (
The LAMPOUT driver also has an over-current blanking
OC(BLANK)
Before OV
T
LIM
or UV
State
OFF
OFF
ON
ON
X
X
hysteresis value is T
to allow for incandescent lamp inrush
OFF
OFF
OFF
ON
OFF
ON
LIM
Returning From
Over-voltage
State When
)
FUNCTIONAL DEVICE OPERATION
T
LIM
LAMP DRIVER OPERATION
) protection scheme
LIM(HYST)
OFF
OFF
OFF
OFF
OFF
OFF
Returning From
Under-voltage
State When
.
T
LIM
), the
33812
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