SCES586D July 2004 – June 2015 SN74LVC1G123
PRODUCTION DATA.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The SN74LVC1G123 can be used for many applications. The application shown here is a switch debounce circuit. Many switches produce multiple triggers when pressed, and the debounce circuit turns the many triggers into one. This circuit takes advantage of the retrigger capability of the SN74LVC1G123 in that the output pulse length only has to be longer than the longest individual bounce (typically less than 1 ms).
The values for VCC, RPU, R, and C must be selected for proper operation.
VCC is selected at 1.8 V. This value is usually driven by the logic voltage of the system, but is arbitrary in this case.
RPU is selected at 10 kΩ.
R and C are selected via the plots in Application Curves and are based on the time desired for the output pulse. In this case, the output pulse will be 1 ms. Since the supply voltage has been selected at 1.8 V, Figure 11 is used to determine the R and C values required. First convert the desired pulse width (tw), 1 ms, to ns. This yields 106 ns. Next follow that line across to see which R and C values intersect it.
R is selected at 10 kΩ because that line intersects nicely with 106 ns and 105 pF, making the selection of C at 0.1 µF easy.
PARAMETER | VALUE |
---|---|
VCC | 1.8 V |
RPU | 10 kΩ |
tw | 1 ms |
R (Rext) | 10 kΩ |
C (Cext) | 0.1 µF |
In addition to the shown components, a 0.1-µF decoupling capacitor from VCC to ground should be placed as close as possible to the device.