33813 Datasheet, PDF (33/54 Pages) Freescale Semiconductor, Inc – One Cylinder Small Engine Control IC

5.1.34 Clamp Active Status Bits
There are two clamp active status bits in the SPI VRS status register. One is for the low pulse clamp and the other is for the high
pulse clamp. When either of these bits are a one (1), it indicates that the peak voltage for that part of the input waveform has
exceeded the clamp voltage and is being clamped to the high or low voltage limit. These status bits can be used to indicate that
the engine has attained the speed necessary to switch from “cranking” values for the threshold and blanking (in the SPI VRS
control register) to the “running” values. (in the SPI VRS configuration register).
5.1.35 Pre-driver Operation
There are three identical pre-drivers in the 33813. Each pre-driver can be configured as either an ignition (IGBT) pre-driver or a
general purpose gate driver (GPGD). By default, one pre-driver is configured as a GPGD (O2HOUT) and two pre-drivers are
configured as ignition (IGNOUT1) pre-drivers.
A bit in each of the SPI Configuration registers, for each pre-driver, defines whether the pre-driver behaves as an ignition or a
GPGD pre-driver.
It should be noted that there are only two current measurement circuits, ISGNSENSP/N and O2SENSP/N. When both pre-drivers
are used as GPGD, then IGNSENSP/N is associated with the IGNOUT1 pre-driver only, and the O2SENSP/N is associated with
the O2OUT pre-driver.
5.1.36 O2HIN Input
The O2HIN pin is the parallel input that controls the O2HOUT pre-driver output. The O2HIN pin is a 5.0 V logic level input with a
built-in pull-down to ground to prevent accidental actuation of the pre-driver output if the connection to the pin is lost. As a default,
the O2HIN input is ORed with the O2HOUT control bit in the SPI ON/OFF control word. This is to allow the O2HOUT to be
controlled by either the O2HIN (parallel input) or via the SPI.
5.1.37 O2HOUT Pre-driver Output with Drain Feedback Input O2HFB
The O2HOUT output is a pre-driver output that controls the gate of a MOSFET to drive a heater on an O2 (Lamda) sensor. The
pre-driver is capable of driving most power MOSFETs. The O2HOUT output and associated drain feedback pin O2HFB provide
short to battery, over-current protection for the external driver MOSFET. More accurate current control can be provided by placing
a current sense resistor between the O2SENSP and O2SENSN pins.
Output-off open circuit (OL) and output-on over-current (OC) faults are detected and annunciated via the SPI.
5.1.38 IGNIN1 Input
The IGNIN1 pin is the parallel inputs that control the IGNOUT1 pre-driver output. The IGNIN1 pin is a 5.0 V logic level input with
a built-in pull-down to ground to prevent accidental actuation of a pre-driver output if the connection to the pin is lost. As a default,
the IGNIN1 input is ORed with the IGNOUT1 control bit in the SPI ON/OFF control word. This is to allow the IGNOUT1 to be
controlled by either the IGNIN1 (parallel input) or via the SPI.
5.1.39 IGNOUT1 Pre-driver Output, with Feedback IGNFB1 and Current
Sense Inputs
The IGNOUT1 output is a pre-driver output that drives an IGBT that controls the ignition coil current to produce a spark. The
IGNOUT1 output and its feedback pins IGNFB1 provide short to battery and one shared current sense resistor provides over-
current protection for the external driver transistors. When used as an IGBT driver, a 10:1 voltage divider (9R:1R) must be used
on the feedback pins to prevent the 400 Volt flyback from damaging the IC.
If two Ignition pre-drivers are not required, they can be reconfigured, via the SPI, as general purpose gate drivers (GPGDs) used
to drive ordinary MOSFETs.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33813
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