Just a WAG from me: Chip drives the gate (base?) of the transistor and provides over current protection. Transistor drives the coil based on the input from PCM. Want more dwell? -> fatten the pulse from PWM. Too much dwell make the pulse less wide.
These are all things the TPU does very well.
Chip is probably there to drive the output transistor and shut things down if there is a short.
I need to get hold of one of these and have a look-see.
Look forward to the pics if you can
-Tom
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