Hi team,
We want to minimize the pull-up resistance in the following figure.
We want to make resistance as small as possible from the viewpoint of immunity.
I want to make it 10kΩ if possible.
Is that possible?
If it is difficult, how much can we make it smaller?
Because it is microampere order, it is assumed that the bias condition does not change significantly.
If you have any concerns, please tell us it.
Best regards,
Tomoaki Yoshida
See [FAQ] How do the LSF translators work?
The primary purpose of the 200 kΩ resistor is not to pull the voltage up to B supply, but to limit the current through the reference transistor. As shown above, the reference transistor regulates itself so that the voltage at the Vref_B pin is always the same, and the voltage between that and the B supply (Vref_B − Vref_A − VTH) is dropped over the resistor.
If you make the resistor smaller, the current through it will be larger. You can make the resistor as small as you want, but please note that the current does not flow to ground; the Vref_A supply must be able to sink this current.
Hi Clemens-san,
Thank you for your support.
In other words, if the power supply on the VrefA side can sink, does it mean that there is no problem using a 10 kΩ resistor?
I think the requirement of Vref_B is VrefA + 0.8V.
I think it will not be able to meet the requirements of Vref_B if the resistance gets too small, but what is the limit?
Best regards,
Tomoaki Yoshida
