Thread: Crank signal valid limits

I know you can't find a diagram.
I can't find the circuit diagram, and neither can anyone else I know of.

So if you don't have a diagram and someone says to you "The chip is near the connectors and is a TLC2272A, and the output you need is on 2Out" what do you do?

For me the obvious answer is "Embrace your inner hacker".

1. Download the TLC2272A datasheet so you have the pin out, TLC2272A | Precision Op Amps | Operational Amplifiers (Op Amps) | Description & parametrics
   
   
2. Remove lid and locate the 8 pin chip located close to the CKP pins. You know it's 8 pin because you read the datasheet.
   
3. Refer to pinout on datasheet for location of 2Out - it's pin 7 on an 8 pin SOIC package.
   
4. With input signal on CKP +/- probe "2Out".

If you have access to an audio interface with a balanced output I'd suggest using that and tap the +ve and -ve phases to drive CKP + and CKP -.

What you are trying to do is find the point the schmitt trigger ceases to latch transitions properly.

I did a quick test with a bitscope micro, a scope probe and using the bitscope onboard signal gen attached to CKP+.

This with a 3.3V sine wave into the CKP+ input, monitoring the output on pin "2out":


And a 40mV sine wave into CKP+


cheers
Paul

It looks like the high speed crank fault is associated with a threshold of 333 rpm.
Can't be certain exactly what other conditions but suspect that it is the combination lack of clean pulse train from the CKP sensor and RPM above 333 that cause this fault.