SCLS467F FEBRUARY 2003 – June 2016 SN74LV123A-Q1
PRODUCTION DATA.
Refer to the PDF data sheet for device specific package drawings
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 SNx4LV123A device is a dual monostable multivibrator. It can be configured for many pulse width outputs and rising or falling-edge triggering. The application shown here could be used to signal separate interruptable inputs on a microcontroller when an input had a rising or falling edge.
NOTE
To prevent malfunctions due to noise, connect a high-frequency capacitor between VCC and GND, and keep the wiring between the external components and Cext and Rext/Cext terminals as short as possible.
The output pulse duration, tw, is determined primarily by the values of the external capacitance (CT) and timing resistance (RT). The timing components are connected as shown in Figure 12.
If CT is ≥1000 pF and K = 1.0, the pulse duration is given by Equation 1:
where
if CT is <1000 pF, K can be determined from Figure 5
Equation 1 and Figure 16 can be used to determine values for pulse duration, external resistance, and external capacitance.
The minimum input retriggering time (tMIR) is the minimum time required after the initial signal before retriggering the input. After tMIR, the device retriggers the output. Experimentally, it also can be shown that to retrigger the output pulse, the two adjacent input signals must be tMIR apart, where tMIR = 0.30 × tw. The retrigger pulse duration is calculated as shown in Figure 13.
The minimum value from the end of the input pulse to the beginning of the retriggered output must be approximately 15 ns to ensure a retriggered output (see Figure 14).