33812 datasheet(15/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33812

FUNCTIONAL DEVICE OPERATION

IGNITION PRE-DRIVER OPERATION

INJOUT Fault Detection Features

Off State, Open Load Detection

An open load on the injector driver is detected by the

voltage level on the drain of the output device in the off state.

Internal to the device is a pull-down current source. In the

event of an open injector the drain voltage is pulled low.

When the voltage crosses the open load detection threshold,

an open load is detected. The open load fault detect

threshold is set internally and is not programmable. The open

load fault is reported as a high logic level on the INJFLT line.

On State, Shorted Load Detection

The INJOUT driver is capable of detecting a shorted

injector load (short to battery) in the on state. A shorted load

fault is reported when the drain pin voltage is greater than the

preset short threshold voltage. The shorted load fault detect

threshold is set internally and is not programmable. The

shorted load fault is reported as a high logic level on the

INJFLT line.

Clearing the INJFLT line

When the INJFLT line goes high for any of the following

reasons, while the INJIN line is high (on state):

• Short to battery

• Over-temperature

• Over-voltage

• Open load

The INJFLT line will remain high until the INJIN line goes

to a low logic level and the returns high (rising edge).

IGNITION PRE-DRIVER OPERATION

The Ignition pre-driver output is controlled by the logic

level input IGNIN. When IGNIN is high the IGNOUTH pin is

pulled high to IGNSUP. When the IGNIN pin is low, the

IGNOUTL line is pulled to ground turning off the driver

Darlington or IGBT.The IGNOUT pre-driver protects the

output device against over-current, short to battery, and

VPWR over-voltage.

IGNOUT OUTPUT PROTECTION FEATURES

Over-current and Short to battery (ILIM)

The Ignition Pre-driver protection scheme senses over-

current in the driver device by monitoring the voltage at the

IGNFB pin. Since this pin is protected by a 10:1 voltage

divider, the over-current threshold voltage is set internally to

1/10 of the voltage expected on the drain or collector of the

output device in an over-current situation. Since the Ignition

output device is external to the 33812, a short to battery is the

same as an over-current fault.

An over-current fault or short to battery is reported as a

high logic level on the IGNFLT line.

Temperature Limit (TLIM)

Since the Ignition output device is external to the 33812,

there is no over-temperature protection provided.

IGNOUT FAULT DETECTION FEATURES

Off State, Open Load Detection

An open load on the ignition driver external device is

detected by the voltage level on the drain or collector of the

output device in the off state (through a 10:1 voltage divider).

In the event of an open ignition coil the drain/collector voltage

is pulled low. When the voltage crosses the open load

detection threshold, an open load is detected. The open load

fault detect threshold is set internally and is not

programmable. An open load fault is reported as a high logic

level on the IGNFLT line.

Over-voltage (VPWR(OV))

The Ignition pre-driver is also protected against an over-

voltage condition:

When the VPWR supply exceeds the VPWR(OV) threshold,

the IGNOUTL and IGNOUTH outputs turn off and stays off

until the over-voltage condition clears and the next rising

edge of the IGNIN input pin.

Clearing the IGNFLT line

When the IGNFLT line goes high for any of the following

reasons, while the IGNIN line is high (on state):

• Short to battery

• Over-voltage

• Over-temperature of the IGNOUTL and IGNOUTH

transistors

• Open load

The IGNFLT line will remain high until the IGNIN line goes

to the low logic level and then returns high.

33812 Datasheet(PDF) 15 Page - Freescale Semiconductor, Inc

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