Dear Customer, I would like to set the output voltage of the TPS61379-Q1 to about 4 patterns using a rotary switch. I would like to fix the upper resistor and change only the lower resistor to set the following voltages: 6V, 5.4V, 4.8V, 4.2V. Please tell me how to calculate the resistors. What should I pay attention to when doing this? Should I insert a capacitor between FB and ground? How large a capacitor would be? Are there any other points I should be careful of? Thank you in advance.

Hello,

user4961418 said:

Please tell me how to calculate the resistors.

You may refer to the datasheet for the feedback resistor calculation. Following is an example for reference.

user4961418 said:

What should I pay attention to when doing this?

I'm not sure that while switching between different tap positions of the rotary switch, whether there will be a short duration that the bottom resistor is open? If so then during this short duration, the TPS61379 can't maintain the Vout, especially if the load is heavy. So in the above reference design, the 100kΩ is always connected. The Vout can at least maintain 4.2V during the short time when the rotary switch is switching between different tap positions.

user4961418 said:

Should I insert a capacitor between FB and ground? How large a capacitor would be?

I think it's no need.

user4961418 said:

Are there any other points I should be careful of?

I think you may pay attention to the possible Vout drop while the rotary switch is switching between different tap positions and check whether it's OK in you application.

Regards

Lei