LTC6752 Pulse Stretcher Width

Hi,

Can you share the LTspice circuit you used?

Hi,

Sorry for the delayed reply. I've used the example provided by AD

https://www.analog.com/media/en/simulation-models/LTspice-demo-circuits/LTC6752_F12.asc

and I have not changed anything in the simulation. I tried to calculate where does this 100ns width  value in the datasheet is coming from (although the spice simulation gives ~120ns) with given C_timing = 100pF and R_timing = 6.65 kOhm values.

Thanks,

Hi,

I would say that the datasheet generally saying that the pulse stretch ~100ns.

Even when we look closely at Figure 12 below, the pulse stretch is ~110ns.

The simulation is off by very little but still close enough to demonstrate how the circuit functions.

Thanks for the insight, but where this ~100ns is coming from? Simple RC or ln(2)RC with R_timing and C_timing  calculation is not the giving me the answer. In the simulation, yes, change in the R_timing or C_timing changes the resultant time, but I cannot figure out how to get ~100ns from the given values.

Hi hikmet, Hi ARoxas,

U2 non-inverting input transitions to 0.5V (R5, R6, R7 action with U1, and U2 output both at 3.3V) after the input high transition pulse. The RC time constant is 665ns (R8, and C2). The pulse stops when U2 inverting input reaches / exceeds 0.5V, "V_stop":

V_stop = 3.3V (1 - e^(-t / 665ns) )

V_stop = 0.5V

Solving this I get 109ns which matches LTspice and Figure 12 application section.

Hope this helps.

Regards,

Hooman

Thank you, Hooman, for the answer. It is much clear now.

Thank you, Hooman, for the answer. It is much clear now.