Original question:
SN74LVC1G123: K, pulse duration constant is depend on Cext or CL ?
Hi TI team,
Appreciated that if TI team could help to confirm that by using Cext = 30pF and potentiometer, Rext from 1kohm to 100kohm can be used to generate the pulse duration of 0.1us, 0.2us, 0.5us, 1us, 5us and 10us.
What are the other factors that may affect the accuracy of the pulse duration ?
Thanks in advanced.
There are five things that will affect the output pulse width of the device if they vary:
(1) Supply voltage
(2) External timing capacitor, C_ext
(3) External timing resistor, R_ext
(4) Temperature
(5) Manufacturing process
1 through 4 are dependent on your system, while 5 is not.
Temperature can cause up to about 2% of variation from our device, however typically the capacitor will have the largest temperature coefficient and will cause the most variation (some can cause greater than 100% variation).
The application report "Designing With the SN74LVC1G123 Monostable Multivibrator (Rev. A)" contains this plot that is from a similar configuration to what you are considering:
Supply voltage variations can cause K to change, and at 3.3V with a 30 pF timing capacitor, K is relatively large and will vary significantly. I do not have data to provide for this capacitor / supply combination. I would recommend including supply variations as part of your prototype testing prior to building a complete system.
Manufacturing process could cause some variation depending on many variables. Unfortunately, our data doesn't isolate this, so I have to discuss this in a more holistic sense.
Looking at our char data, across supply (10%), temperature (-40 to +125C), and process (weak, nominal, strong), the worst case would be a variation of 15% in the output pulse.
the output of the pulse is connected to NPN to level shift up to 12V. May I know any concern for the output pulse duration ?
