555 - Non retriggable one shot circuit

[casemod]

Hi folks,

I am designing a motor control application.

I wish to implement the fault protection in hardware as the micro controller may take too long to respond.

This is my issue currently:
1st:
I thought about using a 555 timer as a one shot triggered, but most circuits will timeout after a while. I wish to either have separate set/reset inputs such as a flip flop or keep it triggered until power is removed. This in turn will disable the output trough a buffer.

2nd:
I need the circuit to actuate in 10uS, the most, so that an output short circuit does not blow the mosfets.
Does the 555 respond in such amount of time, or I am better using some other approach?

Many thanks in advance for your thoughts/tips.
CS

 

[andre_luis]

I wish to implement the fault protection in hardware as the micro controller may take too long to respond

By using micro controller I/O interruption, the action can be performed so immediate as you can optimize service routine, certainly after few instructions.

 

[casemod]

By using micro controller I/O interruption, the action can be performed so immediate as you can optimize service routine, certainly after few instructions.

Few things may happen..

I might have another ISR happening, so Ill have to wait for that to be done for fault ISR is executed.
I might have an over-current situation caused by a software fault. Depending on the fault the ISR may or may not be executed. For example, a CPU freeze.

For the above a an hardware fault circuitry is more suited, at least for the development phase, until everything is properly tested.

 

[Audioguru]

A 555 has a flip-flop inside. Pin 2 triggers it and pin 4 or pin 6 resets it.