Analog Integrated Circuit Device Data



Freescale Semiconductor

30

33814

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 and IGNIN2 Inputs

The IGNIN1 and IGNIN2 pins are the parallel inputs that control the IGNOUT1 and IGNOUT2 pre-driver outputs, respectively.

The IGNIN1 and IGNIN2 pins are 5.0 V logic level inputs with built-in pull-downs to ground to prevent accidental actuation of a

pre-driver output if the connection to the pin is lost. As a default, IGNIN1 and IGNIN2 inputs are ORed with the IGNOUT1 and

IGNOUT2 control bits in the SPI ON/OFF control word. This is to allow the IGNOUTs to be controlled by either the IGNINs

(parallel inputs) or via the SPI.

5.1.39 IGNOUT1 and IGNOUT2 Pre-driver Outputs, with Feedback IGNFB1

and IGNFB2, and Current Sense Inputs

The IGNOUT1 and IGNOUT2 outputs are pre-driver outputs that drive an IGBT that controls the ignition coil current to produce

a spark. The IGNOUTx outputs and their associated feedback pins IGNFBx 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.

More accurate current control can be provided by placing a current sense resistor between the IGNSENSP and IGNSENSN pins.

When both pre-drivers are used as ignition (IGBT) pre-drivers, the both pre-drivers can share one current sense resistor. The

input controls will determine the value of the current sense threshold voltage across the current sense resistor. When either one

When one pre-driver is used as an ignition pre-driver and the other pre-driver is used as a GPGD, the current sense circuit is

connected ONLY to the ignition driver channel. When both pre-drivers are designated as GPGD pre-drivers, only pre-driver #1

will have use of the current sense circuit, the other pre-driver, #2, will only have short to battery protection via the drain sense

voltage comparator.

5.1.40 RESETB

The RESETB pin is a 5.0 volt logic, low level output that is used to reset the MCU.The RESETB pin is an open drain output.

Without power on the 33814 circuit, the RESETB pin is held low by an internal pull-down resistor. In a typical application, the

RESETB pin must be pulled up externally by a pull-up resistor to VCC

When power is applied to the circuit and the voltage on

the VCC pin reaches the lower voltage threshold, the RESETB pin will remain at a low level (open drain FET turned on) for a

pulse is generated due to any of the following events:

1. A watchdog timer timeout event occurs,

2. An under-voltage event on VCC occurs, or

3. An over-voltage event on VPWR occurs.

A Power On Reset (POR) is always provided upon power ON (i.e. anytime the IC goes from sleep state to active state).