Help! DIY 4 amp L297/6203 driver

[Ross77]

Progress so far is three options.

1. Basic . as per data sheet but with half step boost and ne555 controling the idle current reduction
2.Ideal. as basic but with PIC controlling the idle current reduction and shunt reg to stop over voltage (not sure if I need to include the mosfet from the original as well?)
3. Complete. as above but with output short-circuit protection. (not sure about that now as it is quite different fron the data sheet! posted earlier)

Any thoughts, omissions or additions?

[irving2008]

There is an error with the Vref circuitry with the 555... Vref should be connected to the slider of the pot...

[Ross77]

Cheers thats the advantage of a fresh pair of eyes I thought I'd fixed most of the errors.

Any thoughts on using the short circuit protection and if i need the mosfet in the shunt regulator?