TPS62420: Inquire TPS62420 SCH review

Hello Edward,

Your feedback resistor bridges do not have the correct values to regulated those output voltages.

For 1.2V, you should have R12=220kOhm/ R11=220kOhm

and for 3.3V,  R22=220kOhm/ R21=1MOhm.

For an easier debug, you could add an additional 10kOhm resistor on each enable pin that could be removed for further investigation.

If you have any other questions, please ask.

Thank you!

Best Regards,

Dorian 

Hi Dorian,

For 3.3V,  R22=220kOhm/ R21=1MOhm, do you think we can increase R22 and reduce R21 to avoid noise couple?

Thank you.

Edward Chen

Hi user,

You are right, it is important to consider the noise sensitivity here. What is important is to minimize the resistor path to ground on the resistor bridge so the FB leakage current stays low enough. You could use  R22=100kOhm&R21=470kOhm for this.

I recommend you to read this App note, which explains the consideration you need to keep in mind when designing a resistor bridge at feedback:

http://www.ti.com/lit/an/slyt469/slyt469.pdf

Thank you!

Best regards,

Dorian