Hi,
K, constant should be depend on CL or Cext ?
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K is dependent on the timing capacitor, Cext. The load capacitance, CL, should not exceed 50pF.
Can I said that RL and CL is the probe jig behaviour that might affect the output pulse ?
RL and CL are not related to the output pulse width - Cext and Rext are the timing components.
Yes, there is a limitation on RL.
At 3.3V operation, to keep V_OH above 2.3V the output current needs to remain less than 24 mA. To ensure this, use Ohm's Law to calculate resistance:
R = V/I = 3.3 / 0.024 = 137.5 ohms
RL should be larger than 137.5 ohms.
Ok. Understand that. I have my output connect to 549ohm up and down to base of NPN. Do i need to change it to larger resistor ?
The Vbe of NPN is max at 0.7V at 5V with Ic = 2mA.
Could i expect the final output is shifted to 12V after 2 NPN ? Could it have any factor affect the pulse duration ?
I'm afraid I can only support the TI device's operation -- I would recommend simulating your circuit to determine any issues that might arise from using a discrete bipolar level shifter.
We do not, and there's a detailed explanation as to why here:
You may also find these other FAQs helpful:
(+) [FAQ] Monostable Multivibrators - Logic forum - Logic - TI E2E support forums
if this is due to the limitation of the spice model, can i say that there is no way to simulate the circuit until we get the prototype board and test on it ?