Hi,
My customer is using SN74CB3T16211.
Using situation is Vcc=3.3V, IN=3.3V and OUT=3.3V.
He has a issue.
Voltage is outputed when _OE = Low.
After that, Output voltage is decreased as below picture.
Could you advice me about the cause of this issue, please?
Best regards,
Shimizu
Hello Shimizu,
The behavior you are observing appears to be overshoot. Below I have a very simplified circuit to illustrate the concept. However, this is a simplified model and may not match your setup as I do not know what else is in your customer's system besides TI's SN74CB3T16211. In this model, I have included an inductor and some capacitors which together form a resonant circuit and thereby are the primary culprits in the overshoot observed in the accompanying plot. Although your customer may not have an inductor included in their formal schematic, any trace leading to and from the switch will have some amount of parasitic inductance. Within the SN74CB3T16211 there is some capacitance (13 pF) which will add with and board capacitance and additional capacitance from capacitors at the load. The reason that the customer's output eventually settles to a value beneath 3.3V can be attributed to attenuation. If we remove the inductor and capacitors in the model below, the circuit essentially becomes a voltage divider. Rs is the source resistance of your sensor, amplifier, or microcontroller that provides the 3.3V input to the SN74CB3T16211, while RL represents the load resistance. Ron corresponds to the resistance of the SN74CB3T16211.
If RL is relatively low, such as in the example below, the amount of attenuation can be quite noticeable.
Figure 1
