Hello all,
I am using the SN74LVC2G125 buffer to interface a µ-controller with Hall sensor.
The Hall sensor is supplied with +5V. The sensor signal is pulled-up to +5V through a 5 Kohms resistor, and tied to GND through a 1nF capacitor (sensor requirements). This signal comes in entry of the SN74LVC2G125.
The SN74LVC2G125 is supplied with the same +5V supply (decoupling capacitor is 100nF). As it is not used the second input (resp. enable) is tied to GND (resp. Vcc).
The SN74LVC2G125 output goes then to the µC input. The µC has internally a +5V pull-up resistor (5 Kohms), and a capacitor between input and GND (unknown value).
When the Hall sensor state is changing (rising edge or falling edge), here is my problem :
- The +5V supply has big disturbance
- The SN74LVC2G125 goes not "directly" from high state to low state (and conversely), but there are some oscillations that can last for some hundreds of ns / some µs
I tried to solve this by adding to SN74LVC2G125 a capacitor between output and GND (I tried 33pF). The behavior is better, but there are still oscillations.
Shall I add some line resistor (500 ohms) as indicated in the datasheet on § Parameter Measurement Information, page 8, figure "load circuit" ? Or shall I just try different capacitor values until I find the right one ?
Thank you for your help,
Best regards,
Julien