LMC555: Create a Power On Delay?

Go Bravos

Part Number: LMC555
Other Parts Discussed in Thread: TPS3808

Team,

Can the LMC555 be used to create a power on delay? I have three reset groups that have to wait 15ms before the next ones are powered up. So the first one starts at t=15ms, the second one at t=30ms and the third at t=45ms.

The LMC555 datasheet only shows pulse and one shot applications, but I’m looking for would be functionally equivalent to 3 line delays with 15ms taps.

Thank you.

over 4 years ago

0 Ron Michallick over 4 years ago

TI__Guru*** 140686 points

Hello Go,

It looks like you need three. Maybe three timers but I won't say that until I know a little more about the loads and supply voltage.

What is the supply voltage and the load current for the three loads?

Would you like to control the rise time of the three outputs or is 'instant on' prefered?

How accurate does the 15ms need to be?

0 Go Bravos over 4 years ago in reply to Ron Michallick

TI__Expert 6090 points

Ron,

The power on reset function that I need has to produce an output that is initially low until a control is negated, then a programmable amount of time later the output goes high permanently (not pulsed). It’s unclear to me how I could get a power on reset delay with the LMC555 because all I see it producing is either a single pulse (low/high/low) or a clock output.

I’m now leaning towards using three of the TPS3808 devices because I need to have a power on delay that can be retriggered to power cycle a processor module.

Thank you.

0 Ron Michallick over 4 years ago in reply to Go Bravos

TI__Guru*** 140686 points

Go,

You should receive an answer shortly the new thread.

https://e2e.ti.com/support/power-management/f/196/t/902386

Clock & timing

Clock & timing forum

LMC555: Create a Power On Delay?